Bacteriophage Ecology Group
Aquatic Virus References
Dedicated to the ecology and evolutionary biology of the parasites of unicellular organisms (UOPs)
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© Phage et al. last updated on Sunday, July 11, 2004

  1. Association of a bacteriophage with virulence in Vibrio harveyi. Austin,B., Pride,A.C., Rhodie,G.A. (2003). Journal of Fish Diseases 26:55-58. The virulence of Vibrio harveyi, which is a serious pathogen of penaeids (Karunasagar, Pai, Malathi & Karunasagar 1994; Pizzuto & Hirst 1995; Alvarez, Austin, Alvarez & Reyes 1998) and finfish (Kraxberger-Beatty, McGarey, Grier & Lim 1990; Ishimaru & Muroga 1997), has been associated with possession of double haemolysin genes (Zhang, Meaden & Austin 2001). The study seeks to investigate a possible relationship between virulence and the previously described bacteriophage of V. harveyi (Oakey & Owens 2000). The bacteriophage, which has been determined to have an icosahedral head and rigid tail and to contain double stranded linear DNA, has been presumptively assigned to the genus Myovirus (Oakey & Owens 2000). [TOP OF PAGE]

  2. Direct estimates of the contribution of viral lysis and microzooplankton grazing to the decline of a Micromonas spp. population. Evans,C., Archer,S.D., Jacquet,S., Wilson,W.H. (2003). Aquat. Microb. Ecol. 30:207-219. During a mesocosm study in Raunefjorden, Norway, a Micromonas spp. population, initially showing exponential net growth, dramatically declined after Day 4 of the experiment. Using a modification of the dilution approach originally developed to quantify grazing by microzooplankton on phytoplankton, it was possible to partition the mortality of Micromonas spp. between grazing and viral lysis on Days 5, 6 and 7 during the population decline. Parallel dilution experiments were carried out in which 0.2 µm- and 10 kDa-filtered water was used as the diluents. In this way, gradients of grazing pressure (0.2 µm series) and grazing pressure + viral concentration (10 kDa series) were produced. Model 1 linear regression of the fraction of whole water versus the apparent growth rate of chlorophyll a and Micromonas spp. provided an estimate of mortality in the 0.2 µm and 10 kDa dilution series. On Days 5, 6 and 7, the slopes of the linear regressions of 0.2 µm and 10 kDa dilution series were significantly different at p = 0.083, 0.001 and 0.093 respectively. From the differences in slope between the series, estimates of viral mortality amounted to a turnover rate of the Micromonas spp. standing stocks of 10, 25 and 9% d(-1). This compares to a turnover rate by the microzooplankton of 48, 26 and 23% d(-1). On all 3 d the combined viral lysis and grazing mortality exceeded estimates of the potential production of Micromonas spp., in part accounting for the population decline. This study demonstrates that the dilution approach can be adapted to directly determine virus-induced mortality rates of specific phytoplankton. However, further work is required to determine how the specificity of viral infection and variety of viral infection cycles affect the results of this modified dilution approach when applied to other phytoplankton taxa and communities. [TOP OF PAGE]

  3. The physical environment affects cyanophage communities in British Columbia inlets. Frederickson,C.M., Short,S.M., Suttle,C.A. (2003). Microb. Ecol. 46:348-357. Little is known about the natural distribution of viruses that infect the photosynthetically important group of marine prokaryotes, the cyanobacteria. The current investigation reveals that the structure of cyanophage communities is dependent on water column structure. PCR was used to amplify a fragment of the cyanomyovirus gene (g) 20, which codes for the portal vertex protein. Denaturing gradient gel electrophoresis (DGGE) of PCR amplified g20 gene fragments was used to examine variations in cyanophage community structure in three inlets in British Columbia, Canada. Qualitative examination of denaturing gradient gels revealed cyanophage community patterns that reflected the physical structure of the water column as indicated by temperature and salinity. Based on mobility of PCR fragments in the DGGE gels, some cyanophages appeared to be widespread, while others were observed only at specific depths. Cyanophage communities within Salmon Inlet were more related to one another than to communities from either Malaspina Inlet or Pendrell Sound. As well, surface communities in Malaspina Inlet and Pendrell Sound were different when compared to communities at depth. In the same two locations, distinct differences in community composition were observed in communities that coincided with depths of high chlorophyll fluorescence. The observed community shifts over small distances (only a few meters in depth or inlets separated by less than 100 km) support the idea that cyanophage communities separated by small spatial scales develop independently of each other as a result isolation by water column stratification or land mass separation, which may ultimately lead to changes in the distribution or composition of the host community. [TOP OF PAGE]

  4. The complete sequence of marine bacteriophage VpV262 infecting Vibrio parahaemolyticus indicates that an ancestral component of a T7 viral supergroup is widespread in the marine environment. Hardies,S.C., Comeau,A.M., Serwer,P., Suttle,C.A. (2003). Virology 310:359-371. The 46,012-bp sequence of the marine bacteriophage VpV262 infecting the bacterium Vibrio parahaemolyticus is reported. The VpV262 sequence reveals that it is a distant relative of marine Roseophage SIO1, and an even more distant relative of coliphage T7. VpV262 and SIO1 appear to represent a widespread marine phage group that lacks an RNA polymerase gene and is ancestral to the T7-like phages. We propose that this group together with the T7-like phages be designated as the T 7 supergroup. The ancestral head structure gene module for the T7 supergroup was reconstructed by using sensitive biased Psi-blast searches supplemented by statistical support derived from gene order. In the early and replicative segments, these phages have participated in extensive interchange with the viral gene pool. VpV262 carries a different replicative module than SIO1 and the T7-like phages. [TOP OF PAGE]

  5. The vertical distribution and diversity of marine bacteriophage at a station off Southern California. Jiang,S., Fu,W., Chu,W., Fuhrman,J.A. (2003). Microb. Ecol. 45:399-410. Sixty-two bacteriophages were isolated on eight indigenous bacteria from a Pacific Ocean station spanning 887-m vertical depth, on two occasions between 1999 and 2000. On the basis of 16S rRNA sequences, six hosts were tentatively identified to be in the genus Vibrio and the other two were closely related to Altermonas macleodii (W9a) and Pseudoalteromonas spp. (W13a). Restriction fragment length polymorphism (RFLP) analysis of phage genomes using AccI and HapI showed that 16 phages infecting host C4a (Vibrio) displayed 14 unique RFLP patterns. However, identical phages infecting host C4b, C6a, and C6b (all Vibrio) were obtained from both the surface layer and the hypoxic zone at 850 m. Most phage isolates from the second year had a different RFLP pattern but shared genetic similarity to the phages infecting the same host from the previous year based on a hybridization study using phage genome probes. Cluster analysis of RFLP patterns and hybridization results also indicated that phages infecting the same or genetically related hosts, in general, shared higher degrees of homology in spite of the diverse RFLP patterns. Pulsed field gel electrophoresis (PFGE) analysis of native viral genomes indicated a range in genome size from less than 40 to 200 kb, and the dominant band shifted up by about 5-10 kb in the deep samples compared to the shallow ones. Hybridization of phage genome probes with total viral community DNA from various depths suggests these isolates, or at least some of their genes, represent a detectable portion of the natural viral community and were distributed throughout the water column. Thus, the results of this study demonstrated that the genetic diversity of bacteriophage in the ocean is far greater than that of their bacterial hosts. However, host range may have contributed to the evolution of the diverse phage population in the marine environment. [TOP OF PAGE]

  6. Phages of the marine cyanobacterial picophytoplankton. Mann,N.H. (2003). FEMS Microbiol. Rev. 27:17-34. Cyanobacteria of the genera Synechococcus and Prochlorococcus dominate the prokaryotic component of the picophytoplankton in the oceans. It is still less than 10 years since the discovery of phages that infect marine Synechococcus and the beginning of the characterisation of these phages and assessment of their ecological impact. Estimations of the contribution of phages to Synechococcus mortality are highly variable, but there is clear evidence that phages exert a significant selection pressure on Synechococcus community structure. In turn, there are strong selection pressures on the phage community, in terms of both abundance and composition. This review focuses on the factors affecting the diversity of cyanophages in the marine environment, cyanophage interactions with their hosts, and the selective pressures in the marine environment that affect cyanophage evolutionary biology. [TOP OF PAGE]

  7. Bacterial photosynthesis genes in a virus. Mann,N.H., Cook,A., Millard,A., Bailey,S., Clokie,M. (2003). Nature 424:741 A bacteriophage may protect itself and its host against a deadly effect of bright sunlight. [TOP OF PAGE]

  8. Genetic diversity and temporal variation in the cyanophage community infecting marine Synechococcus species in Rhode Island's coastal waters. Marston,M.F., Sallee,J.L. (2003). Appl. Environ. Microbiol. 69:4639-4647. The cyanophage community in Rhode Island's coastal waters is genetically diverse and dynamic. Cyanophage abundance ranged from over 10(4) phage ml(-1) in the summer months to less then 10(2) phage ml(-1) during the winter months. Thirty-six distinct cyanomyovirus g20 genotypes were identified over a 3-year sampling period; however, only one to nine g20 genotypes were detected at any one sampling date. Phylogenetic analyses of g20 sequences revealed that the Rhode Island cyanomyoviral isolates fall into three main clades and are closely related to other known viral isolates of Synechococcus spp. Extinction dilution enrichment followed by host range tests and PCR restriction fragment length polymorphism analysis was used to detect changes in the relative abundance of cyanophage types in June, July, and August 2002. Temporal changes in both the overall composition of the cyanophage community and the relative abundance of specific cyanophage g20 genotypes were observed. In some seawater samples, the g20 gene from over 50% of isolated cyanophages could not be amplified by using the PCR primer pairs specific for cyanomyoviruses, which suggested that cyanophages in other viral families (e.g., Podoviridae or Siphoviridae) may be important components of the Rhode Island cyanophage community. [TOP OF PAGE]

  9. [Development of cyanobacterial phages at the Institute of Microbiology and Virology of the National Academy of Sciences of Ukraine (History and perspectives)]. Mendzhul,M.I., Lysenko,T.G., Syrchin,S.A. (2003). Mikrobiol. Zh. 65:133-140. The paper deals with the basic trends of fundamental investigations of the Department of Algae Viruses in the field of cyanophagia-ecology, biological and physico-chemical properties of cyanophages as well as interrelation with the host cells. Such problems as a possibility to use the system cyanophage-cyanobacteria as the experimental model for development of the unified functional model of productive infection, efficient methods of prophylaxis and therapy of virus infections as well as the solution of various biotechnological problems are discussed. [TOP OF PAGE]

  10. [Comparative characteristics of native proteinases of the cyanobacteria Plectonema boryanum and Anabaena variabilis and those induced by cyanophages]. Mendzhul,M.I., Perepelytsia,S.I. (2003). Mikrobiol Zh 65:21-28. Physico-chemical and catalytic properties of proteinases of native and induced cells of cyanobacteria Plectonema boryanum have been comparatively studied. It has been established that at early stages of reproduction of cyanophage LPP-3 in cyanobacteria P. boryanum is formed de novo proteinase complex consisting at least of five enzymes. Proteinases induced by the virus are distinguished from those of native cells by a series of physico-chemical characteristics and possess higher catalytic activity. Analogous virus-induced changes in proteinase complex also occur in the system cyanobacterium Anabaena variabilis--cyanophage A-1. Possible functions of certain enzymes of proteinase complex in the virus pathology of cyanobacteria cells are discussed in the paper. [TOP OF PAGE]

  11. Virus-induced transfer of organic carbon between marine bacteria in a model community. Middelboe,M., Riemann,L., Steward,G.L., Hansen,V., Nybroe,O. (2003). Aquat. Microb. Ecol. ???:??? [TOP OF PAGE]

  12. Spatial distribution of viruses and relation to bacterial activity in a coastal marine sediment. Middelboe,M., Glud,R.N., Finster,K. (2003). Limnol. Oceanogr. ???:??? [TOP OF PAGE]

  13. Genomes of two lysogenic marine phage that infect Vibrio paraheamolyticus. Rohwer,F., Seguritan,V., Feng,I., Segall,A. (2003). [TOP OF PAGE]

  14. Virus succession observed during an Emiliania huxleyi bloom. Schroeder,D., Oke,J., Malin,G., Wilson,W.H. (2003). Appl. Environ. Microbiol. 69:2484-2490. Denaturing gradient gel electrophoresis was used as a molecular tool to determine the diversity and to monitor population dynamics of viruses that infect the globally important coccolithophorid Emiliania huxleyi. We exploited variations in the major capsid protein gene from E. huxleyi-specific viruses to monitor their genetic diversity during an E. huxleyi bloom in a mesocosm experiment off western Norway. We reveal that, despite the presence of several virus genotypes at the start of an E. huxleyi bloom, only a few virus genotypes eventually go on to kill the bloom. [TOP OF PAGE]

  15. Cyanophages infecting the oceanic cyanobacterium Prochlorococcus. Sullivan,M.B., Waterbury,J.B., Chisholm,S.W. (2003). Nature 424:1047-1051. Prochlorococcus is the numerically dominant phototroph in the tropical and subtropical oceans, accounting for half of the photosynthetic biomass in some areas. Here we report the isolation of cyanophages that infect Prochlorococcus, and show that although some are host-strain-specific, others cross-infect with closely related marine Synechococcus as well as between high-light- and low-light-adapted Prochlorococcus isolates, suggesting a mechanism for horizontal gene transfer. High-light-adapted Prochlorococcus hosts yielded Podoviridae exclusively, which were extremely host-specific, whereas low-light-adapted Prochlorococcus and all strains of Synechococcus yielded primarily Myoviridae, which has a broad host range. Finally, both Prochlorococcus and Synechococcus strain-specific cyanophage titres were low (< 10(3) ml(-1)) in stratified oligotrophic waters even where total cyanobacterial abundances were high (> 10(5) cells x ml(-1)). These low titres in areas of high total host cell abundance seem to be a feature of open ocean ecosystems. We hypothesize that gradients in cyanobacterial population diversity, growth rates, and/or the incidence of lysogeny underlie these trends. [TOP OF PAGE]

  16. Wide geographic distribution of bacteriophages that lyse the same indigenous freshwater isolate (Sphingomonas sp. strain B18). Wolf,A., Wiese,J., Jost,G., Witzel,K.P. (2003). Appl. Environ. Microbiol. 69:2395-2398. An indigenous freshwater bacterium (Sphingomonas sp. strain B18) from Lake Plubetasee (Schleswig-Holstein, Germany) was used to isolate 44 phages from 13 very different freshwater and brackish habitats in distant geographic areas. This bacterial strain was very sensitive to a broad spectrum of phages from different aquatic environments. Phages isolated from geographically distant aquatic habitats, but also those from the same sample, were diverse with respect to morphology and restriction pattern. Some phages were widely distributed, while different types coexisted in the same sample. It was concluded that phages could be a major factor in shaping the structure of bacterial communities and maintaining a high bacterial diversity. [TOP OF PAGE]

  17. Fundamental changes in light scattering associated with infection of marine bacteria by bacteriophage. Balch,W.M., Vaughn,J.M., Novotny,J.F., Drapeau,D.T., Goes,J.I., Booth,E., Lapierre,J.M., Vining,C.L., Ashe,A., Vaughn,J.J. (2002). Limnol. Oceanogr. 47:1554-1561. Bacteria and phytoplankton are key determinants of the ocean's inherent optical properties. Despite their high abundance, marine viruses have generally been thought to play a minor role in ocean optics because of their small scattering cross-sections. Nevertheless, the role of specific viral infection on the optical properties of bacteria and phytoplankton has remained unknown (i.e., as viruses disrupt micron-sized host cells to produce submicron cell debris). Here, we used laboratory and mesocosm cultures of marine bacteria for virus infection experiments in which growth conditions and host-virus specificity were controlled. We report that the chief optical impact of viruses is associated with infection and lysis of their hosts. We quantitatively describe, for the first time, two optical changes associated with infection and lysis of marine bacteria by bacteriophage: (1) rapid, strong shifts in the magnitude and shape of the optical volume scattering function and (2) rapid production of colored dissolved organic material. Qualitatively, these changes result in nearly complete clearing of turbid host bacterial suspensions. Although some optical differences would be expected between infection of bacteria in laboratory cultures versus field populations (mainly because of differences in cell size), these results are applicable to the field, especially for dense host suspensions such as in blooms. Even in nonbloom situations, as long as the host bacteria contribute a significant amount of the total particle backscattering, we expect that virus-induced backscattering changes would be detectable by use of satellite or aircraft remote-sensing techniques. [TOP OF PAGE]

  18. Genomic analysis of uncultured marine viral communities. Breitbart,M., Salamon,P., Andresen,B., Mahaffy,J.M., Segall,A.M., Mead,D., Azam,F., Rohwer,F. (2002). Proc. Natl. Acad. Sci. USA 99:14250-14255. Viruses are the most common biological entities in the oceans by an order of magnitude. However, very little is known about their diversity. Here we report a genomic analysis of two uncultured marine viral communities. Over 65% of the sequences were not significantly similar to previously reported sequences, suggesting that much of the diversity is previously uncharacterized. The most common significant hits among the known sequences were to viruses. The viral hits included sequences from all of the major families of dsDNA tailed phages, as well as some algal viruses. Several independent mathematical models based on the observed number of contigs predicted that the most abundant viral genome comprised 2-3% of the total population in both communities, which was estimated to contain between 374 and 7,114 viral types. Overall, diversity of the viral communities was extremely high. The results also showed that it would be possible to sequence the entire genome of an uncultured marine viral community. [TOP OF PAGE]

  19. On the stability properties of a stochastic model for phage-bacteria interaction in open marine environment. Carletti,M. (2002). Math. Biosci. 175:117-131. In this paper we extend the deterministic model for the epidemics induced by virulent phages on bacteria in marine environment introduced by Beretta and Kuang [Math. Biosci. 149 (1998) 57], allowing random fluctuations around the positive equilibrium. The stochastic stability properties of the model are investigated both analytically and numerically suggesting that the deterministic model is robust with respect to stochastic perturbations. [TOP OF PAGE]

  20. Genomic sequence and evolution of marine cyanophage P60: a new insight on lytic and lysogenic phages. Chen,F., Lu,J. (2002). Appl. Environ. Microbiol. 68:2589-2594. The genome of cyanophage P60, a lytic virus which infects marine Synechococcus WH7803, was completely sequenced. The P60 genome contained 47,872 bp with 80 potential open reading frames that were mostly similar to the genes found in lytic phages like T7, fYeO3-12, and SIO1. The DNA replication system, consisting of primase-helicase and DNA polymerase, appeared to be more conserved in podoviruses than in siphoviruses and myoviruses, suggesting that DNA replication genes could be the critical elements for lytic phages. Strikingly high sequence similarities in the regions coding for nucleotide metabolism were found between cyanophage P60 and marine unicellular cyanobacteria. [TOP OF PAGE]

  21. Occurrence and levels of indicator bacteriophages in bathing waters throughout Europe. Contreras-Coll,N., Lucena,F., Mooijman,K., Havelaar,A., Pierz,V., Boque,M., Gawler,A., Holler,C., Lambiri,M., Mirolo,G., Moreno,B., Niemi,M., Sommer,R., Valentin,B., Wiedenmann,A., Young,V., Jofre,J. (2002). Water Res. 36:4963-4974. Somatic coliphages, F-specific RNA bacteriophages, bacteriophages infecting Bacteroides fragilis, Escherichia coli and enterococci were counted in bathing waters in the late spring and summer. We tested fresh and marine bathing waters from North, South, East and West Europe expected to contain between 100 and 500 E. coli per 100 ml, although wider ranges were sometimes found. Bacteriophages were counted after concentration, since a preliminary study proved that this step was necessary to obtain positive counts. During monitoring, a first-line quality control with reference materials for bacteria and bacteriophages was performed by all the laboratories participating in the study. The same microbes were also counted in raw sewage samples from various areas in Europe, where the bacterial indicators and the three groups of bacteriophages were detected in roughly the same numbers. All groups of bacteriophages were detected in both fresh and marine bathing waters throughout Europe. Reliable and complete results from 147 samples showed that for log-transformed values, E. coli and bacteriophages were slightly correlated. However, the slope of the regression line changed according to E. coli concentration and the correlation diminished when this concentration was close to zero per 100 ml. The ratios between E. coli and phages in bathing waters differed significantly from those in sewage. The relative amounts of bacteriophages, mainly somatic coliphages and phages infecting Bact. fragilis RYC2056, increased in bathing waters with low E. coli concentration, especially in seawater samples containing < 100 E. coli per 100 ml. The relationship of bacteriophages with respect to enterococci paralleled that of bacteriophages with respect to E. coli. Somatic coliphages and bacteriophages infecting Bact. fragilis are useful to predict the presence of some pathogens with the same origin as present bacterial indicators but with higher survival rates. [TOP OF PAGE]

  22. High control of bacterial production by viruses in a eutrophic oxbow lake. Fischer,U.R., Velimirov,B. (2002). Aquat. Microb. Ecol. 27:1-12. The aim of the study was to test the hypothesis that the magnitude of viral control on bacterial production in a eutrophic oxbow lake of the River Danube would be higher than all average values reported so far in the literature. This assumption was based on the findings of low grazing of heterotrophic nanoflagellates (HNF) in this system, accounting on average for 5% of the bacterial mortality. Several approaches (viral decay method, estimation of the frequency of infected bacterial cells) to determine viral control of bacterial production were applied on a comparative basis. All system-specific parameters necessary to describe virus-bacteria interactions (burst size, bacterial production, contact rates) were monitored simultaneously. The average viral control of bacterial production determined by the different approaches was similar, ranging from 55.7 to 62.7 %, and prevailing over HNF grazing by a factor of more than 11. For individual events, however, we observed large variations between the methods, indicating that the use of one single method is not reliable to decide whether a detected trend is representative of a specific system. We discuss error sources of the applied methods and mathematical models, and accounted for them when calculating the contribution of viruses to bacterial mortality. We demonstrated that viruses could control more than 100 % of the bacterial production in the Alte Donau, which implies that occasionally up to 1.6 % h-1 of the bacterial standing stock was removed from the water column. High bacterial mortality due to viruses indicated that a large amount of dissolved organic carbon might be recycled from bacteria by phage-induced cell lysis. On average 15.2 mu g C l-1 d-1, corresponding to some 46 % of the bacterial secondary production (BSP), was released into the water column due to viral lysis of bacterial cells and again became available for microheterotrophic consumption. [TOP OF PAGE]

  23. Prokaryotic and viral diversity patterns in marine plankton. Fuhrman,J.A., Griffith,J., Schwalbach,M. (2002). Ecol. Res. 17:183-194. Prokaryotes and viruses play critical roles in marine ecosystems, where they are both highly abundant and active. Although early work on both prokaryotes and viruses revealed little of their diversity, molecular biological approaches now allow us to break apart these 'black boxes.' The most revealing methods have been cloning and sequencing of 16S rRNA genes, community fingerprinting (such as terminal restriction fragment length polymorphism; TRFLP), and fluorescent in situ hybridization. Viral diversity can now be analyzed by pulsed field gel electrophoresis (PFGE) of viral genomes. The present paper summarizes recent advances in bacterial and virus diversity studies, and presents examples of measurements from polar, tropical, and temperate marine waters. Terminal restriction fragment length polymorphism shows that many of the same operationally defined prokaryotic taxa are present in polar and tropical waters, but there are also some unique to each environment. By one measure, a sample from over a Philippine coral reef had about 100 operationally defined taxa, whereas one from the open tropical Atlantic had about 50 and from the icy Weddell Sea, about 60. Pulsed field gel electrophoresis of two depth profiles, to 500 m, from Southern California, measured 2 months apart, shows striking similarities in viral genome length diversity over time, and some distinct differences with depth. The euphotic zone samples had extremely similar apparent diversity, but samples from 150 m and 500 m were different. An obvious next step is to compare the bacterial and viral diversity patterns, because theory tells us they should be related. [TOP OF PAGE]

  24. Sunlight inactivation of human enteric viruses and fecal bacteria. Fujioka,R.S., Yoneyama,B.S. (2002). Water Sci. Technol. 46:291-295. Three human enteric viruses (poliovirus, echovirus, coxsackievirus) suspended in seawater or buffer were stable for 6 hr in the absence of sunlight but were inactivated at the same rate in the presence of sunlight. Under summer sunlight conditions, at least 3 logs of these viruses were inactivated by one-hit kinetics while under winter sunlight conditions only 1 log of these viruses was inactivated by two-hit kinetics. Under these same conditions, 6 logs of E. coli were inactivated within 1 hr by one-hit kinetics under summer and winter conditions. In comparison, E. faecalis was inactivated by two-hit kinetics and only 2.5 logs of inactivation were observed after 4 hr of exposure to winter sunlight. Since human enteric viruses are considerably more resistant to sunlight inactivation than E. coli and moderately more resistant than E. faecalis, marine recreational water quality standards should be based on concentrations of enterococci and not on coliform bacteria. Since the mechanism and rate of inactivation of coliphage and human enteric viruses are similar, coliphages appear to be the best indicator for the presence of human enteric viruses in recreational waters, especially coastal waters where abundant sunshine is available. [TOP OF PAGE]

  25. Bacteriophage replication and reactivation in stationary phase hosts. Gallimore,W.H., Burgess,J.M., Kokjohn,T.A. (2002). Research Signpost 6:467-476. Bacteriophage dynamics in stationary phase or stressed bacterial hosts are poorly understood. Using one-step growth experiments we have demonstrated that stationary phase does not constitute an absolute block to phage multiplication, although latent periods are extended and burst sizes decreased substantially compared to exponential phase infections. Using infectious center assays to quantify lysogen responses to DNA damage revealed that while there was a range of sensitivity to ultraviolet (UV) radiation, no prophages were induced by sunlight exposure. Comparing the capacity of exponential phase and stationary phase cells to resist UV irradiation and reactivate UV-damaged phage revealed that cells maintained in the stationary phase at the time of infection expressed significantly higher levels of DNA repair. Photoreactivation experiments in stationary phase hosts revealed that light-mediated reversal of phage DNA damage definitely occurred in stationary phase bacterial hosts. Our experiments demonstrate that many bacteriophages multiply actively and are competent to reverse DNA damage in post exponential phase host cells. In order to establish the scope and significance of bacteriophages to aquatic ecosystem ecology a more complete understanding of virus dynamics in both growing and stationary phase hosts is essential. [TOP OF PAGE]

  26. Observations on cyanobacterial population collapse in eutrophic lake water. Gons,H.J., Ebert,J., Hoogveld,H.L., van den Hove,L., Pel,R., Takkenberg,W., Woldringh,C.J. (2002). Antonie van Leeuwenhoek 81:319-326. In two laboratory-scale enclosures of water from the shallow, eutrophic Lake Loosdrecht (the Netherlands), the predominating filamentous cyanobacteria grew vigorously for 2 weeks, but then their populations simultaneously collapsed, whereas coccoid cyanobacteria and algae persisted. The collapse coincided with a short peak in the counts of virus-like particles. Transmission electron microscopy showed the morphotype Myoviridae phages, with isometric heads of about 90 nm outer diameter and > 100-nm long tails, that occurred free, attached to and emerging from cyanobacterial cells. Also observed were other virus-like particles of various morphology. Similar mass mortality of the filamentous cyanobacteria occurred in later experiments, but not in Lake Loosdrecht. As applies to lakes in general, this lake exhibits high abundance of virus-like particles. The share and dynamics of infectious cyanophages remain to be established, and it is as yet unknown which factors primarily stabilize the host-cyanophage relationship. Observations on shallow, eutrophic lakes elsewhere indicate that the cyanophage control may also fail in natural water bodies exhibiting predominance of filamentous cyanobacteria. Rapid supply of nutrients appeared to be a common history of mass mortality of cyanobacteria and algae in laboratory and outdoor enclosures as well as in highly eutrophic lakes. [TOP OF PAGE]

  27. [Action of Spirulina platensis on bacterial viruses]. Gorobets,O.B., Blinkova,L.P., Baturo,A.P. (2002). Zh. Mikrobiol. Epidemiol. Immunobiol. 18-21. The impact of the biomass of the blue-green microalga (cyanobacterium) S. platensis on bacteriophage T4 (bacterial virus) has been evaluated. The study revealed that the addition of S. platensis biomass into the agar nutrient medium, followed by sterilization with 2% chloroform and thermal treatment, produced an inhibiting or stimulating effect on the reproduction of the bacteriophage in Escherichia coli B cells, depending on the concentration of S. platensis and the multiplicity of phage infection, as well as on the fact whether the microalgae were added during the first cycle of the development of the virus. The reproduction of the bacteriophage in E. coli B was influenced by the method and duration of the sterilization of the nutrient medium with S. platensis. [TOP OF PAGE]

  28. Viral distribution and activity in Antarctic waters. Guixa-Boixereu,N., Vaque,D., Gasol,J.M., Sanchez-Camara,J., Pedros-Alio,C. (2002). Deep-Sea Research II 49:827-845. Variability in abundance of virus-like particles (VLP), VLP decay rates and prokaryotic mortality due to viral infection were determined in three Antarctic areas: Bellingshausen Sea, Bransfield Strait and Gerlache Strait, during December 1995 and February 1996. VLP abundance showed very small spatial variability in the three areas (7 x 106-2 x 107 VLP ml-1). VLP abundance, on the other hand, decreased one order of magnitude from the surface to the bottom, in two stations where deep vertical profiles were sampled. Low seasonal variability in VLP abundance was found when comparing each area separately. Diel VLP variability was also very low. VLP abundance showed the lowest values when solar irradiation was maximal, in two of the three stations where diel cycles were examined. Viral decay rates (VDR) were determined using KCN in two kinds of experiments. Type 1 experiments were performed in 6 stations to determine viral decay. Type 2 experiments were carried out in 2 stations to examine the influence of temperature and organic matter concentration on viral decay. VDR was not influenced by these parameters. Prokaryotic mortality due to viral infection was always higher than that due to bacterivores in the stations where both factors of prokaryotic mortality were measured. Viral infection accounted for all the prokaryotic heterotrophic production in Bellingshausen Sea and Gerlache Strait and for half of the prokaryotic heterotrophic production in Bransfield Strait. These high values of prokaryotic mortality due to viral infection are difficult to reconcile in nature, and more work is necessary to determine the mechanisms involved in the disappearance of viruses. [TOP OF PAGE]

  29. Use of signal-mediated amplification of RNA technology (SMART) to detect marine cyanophage DNA. Hall,M.J., Wharam,S.D., Weston,A., Cardy,D.L.N., Wilson,W.H. (2002). BioTechniques 32:604-611. Here, we describe the application of an isothermal nucleic acid amplification assay, signal-mediated amplification of RNA technology (SMART), to detect DNA extracted from marine cyanophages known to infect unicellular cyanobacteria from the genus Synechococcus. The SMART assay is based on the target-dependent production of multiple copies of an RNA signal, which is measured by an enzyme-linked oligosorbent assay. SMART was able to detect both synthetic oligonucleotide targets and genomic cyanophage DNA using probes designed against the portal vertex gene (g20). Specific signals were obtained for each cyanophage strain (S-PM2 and S-BnMI). Nonspecific genomic DNA did not produce false signals or inhibit the detection of a specific target. In addition, we found that extensive purification of target DNA may not be required since signals were obtained from crude cyanophage lysates. This is the first report of the SMART assay being used to discriminate between two similar target sequences. [TOP OF PAGE]

  30. Flow cytometric analysis of an Emiliania huxleyi bloom terminated by viral infection. Jacquet,S., Heldal,M., Iglesias-Rodriguez,D., Larsen,A., Wilson,W.H. (2002). Aquat. Microb. Ecol. 27:111-124. During a field mesocosm experiment conducted in coastal waters off western Norway, 11 m(3) enclosures were filled with unfiltered seawater and enriched daily with different nitrate and phosphate concentrations in order to induce a bloom of the coccolithophorid Emiliana huxleyi under different nutrient regimes. Flow cytometry (FCM) analysis was performed 5 times d(-1) in order to follow the initiation, development and termination of the bloom as well as the production of large virus-like particles (LVLPs) identified as E. huxleyi viruses (EhV). EhV production was observed first in the enclosure where N was in excess, and P limitation induced a lower burst size compared to nitrate-replete enclosures. These observations suggest a critical role for both P and N in E. huxleyi-EhV interactions. Concomitant to EhV production, a shift was observed between the original population (coccolith-bearing cells) towards a population characterized by the same chlorophyll a (chl a) fluorescence but with lower right angle light scatter values. This population is likely to correspond to either senescent cells losing their coccoliths or cells characterized by a lower production of coccoliths possibly due to viral infection. At the end of experiment, a significant proportion of E. huxleyi had survived after the end of the bloom. This suggests either the presence of a resistant form of the coccolithophorid or a change in the dominance of different host and/or viral strains during the bloom. A periodical pattern in virus production was recorded with virus number decreasing during the second part of the day suggesting that virus production may be synchronized to the daily light cycle. Our results provide new insights towards the understanding of the relationship between a key marine species and its specific virus. [TOP OF PAGE]

  31. Degree of ultraviolet radiation damage and repair capabilities are related to G+C content in marine vibriophages. Kellogg,C.A., Paul,J.H. (2002). Aquat. Microb. Ecol. 27:13-20. A key issue in the ecology of viruses in the marine environment is the rate of viral production and decay. The ultraviolet (UV) radiation in sunlight has been found to cause loss of infectivity in marine bacteriophages at rates nearly equal to all other decay mechanisms combined. There are 2 main host-mediated mechanisms that can repair UV-damaged phage DNA: photoreactivation and excision repair. Both these mechanisms were investigated in 2 marine Vibrio parahaemolyticus hosts as they catalyzed the reactivation of 7 phages. Photoreactivation was the dominant repair mode in all but one case. A significant correlation was found between G+C content of the phage DNAs (16 to 70 %) and degree of DNA damage (r = 0.955), indicating a strong relationship between the number of thymine dimer targets and the capability to photoreactive DNA damage. Evolution of high G+C content may be a strategy for protection from UV damage in marine phages. [TOP OF PAGE]

  32. Viruses causing lysis of the toxic bloom-forming alga, Heterosigma akashiwo (Raphidophyceae), are widespread in coastal sediments of British Columbia, Canada. Lawrence,J.E., Chan,A.M., Suttle,C.A. (2002). Limnol. Oceanogr. 47:545-550. Viruses that infect and cause lysis of the toxic alga Heterosigma akashiwo are abundant and widespread in the Strait of Georgia, Canada, and adjacent inlets during the summer months when blooms of this alga occur. Because viruses are subjected to many mechanisms of removal and their host is intermittently dormant, the persistence of viruses may be dependent on environmental reservoirs. We extracted pore water from sediments collected in the Strait of Georgia and screened for the presence of infectious agents that cause lysis of H. akashiwo. Lytic agents were widespread throughout the study region, being detected in 17 of 20 sites surveyed. Lytic agents were present in sediments ranging from highly organic to clay-rich and were retrieved from cores taken at water depths of 25-285 m. The highest concentration of lytic agents was found at the sediment-water interface; however, lytic agents were found as deep as 40 cm below the sediment-water interface. Examination of agents isolated from various sites revealed virus-like particles similar to50 nm in diameter. These are similar to other virus-like particles that have been isolated that infect this alga. This suggests that the most abundant lytic agents in the sediments are viruses and that these viruses may be long-lived once buried in the sediments. The widespread presence of viral-size lytic agents that infect H. akashiwo is consistent with viral infection being a mortality agent of this alga in the overlying waters and suggests that they may play in important role in regulating their population dynamics. [TOP OF PAGE]

  33. Plankton blooms: Lysogeny in marine Synechococcus. McDaniel,L., Houchin,L.A., Williamson,S.J., Paul,J.H. (2002). Nature 415:496 Viral infection of bacteria can be lytic, causing destruction of the host cell, or lysogenic, in which the viral genome is instead stably maintained as a prophage within its host. Here we show that lysogeny occurs in natural populations of an autotrophic picoplankton (Synechococcus) and that there is a seasonal pattern to this interaction. Because lysogeny confers immunity to infection by related viruses, this process may account for the resistance to viral infection seen in common forms of autotrophic picoplankton. We undertook a seasonal study in Tampa Bay, Florida, of prophage induction in cyanobacteria over the year ending in October 2000 to find out whether lysogeny occurs in natural Synechococcus populations and, if so, how it is affected by changing environmental conditions. [TOP OF PAGE]

  34. Regeneration of dissolved organic matter by viral lysis in marine microbial communities. Middelboe,M., Lyck,P.G. (2002). Aquat. Microb. Ecol. 27:187-194. The influence of viruses on bacterial net growth and respiration was investigated in batch cultures with natural assemblages of marine bacterioplankton, which were manipulated with respect to abundance of natural virioplankton. In 1 set of cultures (-virus), a virus-free water sample (0.02 mu m filtered) was inoculated with a bacterioplankton concentrate, and in a parallel set of cultures (control) a virus-containing water sample (0.2 mu m filtered) was inoculated with the bacterioplankton concentrate. The 0.02 mu m filtration procedure reduced viral abundance by 62 to 92% in the -virus cultures relative to the parallel control cultures with the natural density of viruses (i.e. the fraction of natural viruses < 0.2 mu m). This approach allowed us to examine the effects of reduced viral densities on the production of natural assemblages of bacteria and viruses and on the distribution of added 3H-thymidine into size fractions (the bacterial size fraction, viral size fraction, dissolved size fraction and respired fraction). The results showed significantly higher bacterial net growth and growth efficiency in cultures with a reduced abundance of viruses relative to control cultures with natural viral abundance, and indicated viral regulation of bacterial abundance in the control cultures. We suggest that viral lysis significantly affected the bacterial carbon cycling in the cultures by liberating a fraction of the organic matter already taken up by the bacteria, thus stimulating recycling of bacterial carbon and reducing the net bacterial production. The implications of such regeneration of dissolved organic matter by viral lysis for pelagic carbon cycling and for measurements of bacterial production are discussed. [TOP OF PAGE]

  35. Virus-like particle analysis in a seston-rich coastal pond using transmission electron microscopy. Montanie,H., Hartmann,H.J., Crottereau,C., Trichet,C. (2002). Aquat. Microb. Ecol. 28:105-115. A method was developed to analyse virus-like particles (VLPs) in seston-rich waters and to quantify their dynamics in a coastal marsh of the Bay of Biscay, French Atlantic coast. The method combined clarification and concentration steps with electron microscopy to obtain information on particle abundance, type and size distribution (e.g. presence of tailed phages, Fuselloviridae, etc.). The mean recovery rates of T2-phages using this method were 71 to 79%, higher than other published rates. The transmission electron microscopy (TEM) counts were validated with T2 plaque lysis assay and epifluorescent (DAPI-stained) particle counting: the TEM method was valid for environmental particle concentrations above 1 to 2 x 106 VLP ml-1; TEM counts were lower than T2-plaque counts (TEM/lysis median = 0.293) but higher than DAPI counts (TEM/DAPI median = 2.39). The method was used to evaluate the coupling between viral and bacterial dynamics in a marsh pond during 2 months. The VLP abundance varied from 1 to 30 x 106 ml super(-1) and the viral population was dominated by small particles (20 to 64 nm). Tailed phages, identified as bacteriophages, were always less abundant than non-tailed VLPs (4 to 23% of total virus), yet their dynamics were better linked with bacterial development than those of total virus. Our results demonstrate that the best way to characterise bacterial lysis from virus in seston-rich coastal environments would be to study the dynamics of tailed phages and virus size-classes rather than the commonly applied total VLPs. [TOP OF PAGE]

  36. Lysogeny and lytic viral production during a bloom of the cyanobacterium Synechococcus spp. Ortmann,A.C., Lawrence,J.E., Suttle,C.A. (2002). Microb. Ecol. 43:225-231. Lytic viral production and lysogeny were investigated in cyanobacteria and heterotrophic bacteria during a bloom of Synechococcus spp. in a pristine fjord in British Columbia, Canada. Triplicate seawater samples were incubated with and without mitomycin C and the abundances of heterotrophic bacteria, cyanobacteria, total viruses and infectious cyanophage were followed over 24 h. Addition of mitomycin C led to increases in total viral abundance as well as the abundance of cyanophages infecting Synechococcus strain DC2. Given typical estimates of burst size, these increases were consistent with 80% of the heterotrophic bacteria and 0.6% of Synechococcus cells being inducible by the addition of mitomycin C. This is the highest percentage of lysogens reported for a natural microbial community and demonstrates induction in a marine Synechococcus population. It is likely that the cyanophage production following the addition of mitomycin C was much higher than that titered against a single strain of Synechococcus; hence this estimate is a minimum. In untreated seawater samples, lytic viral production was estimated to remove ca. 27% of the gross heterotrophic bacterial production, and a minimum of 1.0% of the gross cyanobacterial production. Our results demonstrate very high levels of lysogeny in the heterotrophic bacterial community, outside of an oligotrophic environment, and the presence of inducible lysogens in Synechococcus spp. during a naturally occurring bloom. These data emphasize the need for further examination of the factors influencing lytic and lysogenic viral infection in natural microbial communities. [TOP OF PAGE]

  37. Marine phage genomics. Paul,J.H., Sullivan,M.B., Segall,A.M., Rohwer,F. (2002). Comparative Biochemistry and Physiology 133:463-476. Marine phages are the most abundant biological entities in the oceans. They play important roles in carbon cycling through marine food webs, gene transfer by transduction and conversion of hosts by lysogeny. The handful of marine phage genomes that have been sequenced to date, along with prophages in marine bacterial genomes, and partial sequencing of uncultivated phages are yielding glimpses of the tremendous diversity and physiological potential of the marine phage community. Common gene modules in diverse phages are providing the information necessary to make evolutionary comparisons. Finally, deciphering phage genomes is providing clues about the adaptive response of phages and their hosts to environmental cues. [TOP OF PAGE]

  38. A filterable lytic agent obtained from a red tide bloom that caused lysis of Karenia brevis (Gymnodinum breve) cultures. Paul,J.H., Houchin,L., Griffin,D., Slifko,T., Guo,M., Richardson,B., Steidinger,K. (2002). Aquat. Microb. Ecol. 27:21-27. A filterable lytic agent (FLA) was obtained from seawater in the southeastern Gulf of Mexico during a red tide bloom that caused lysis of Karenia brevis (formerly Gymnodinium breve) Piney Island. This agent was obtained from <0.2 mu m filtrates that were concentrated by ultrafiltration using a 100 kDa filter. The FLA was propagated by passage on K. brevis cultures, and the filtered supernatants of such cultures resulted in K. brevis lysis when added to such cultures. The lytic activity was lost upon heating to 65 degree C or by 0.02 mu m filtration. Epifluorescence and transmission electron microscopy (TEM) of supernatants of K. brevis cultures treated with the lytic agent indicated a high abundance of viral particles (4 x 109 to 7 x 109 virus-like particles [VLPs] ml-1) compared to control cultures ( similar to 107 ml-1). However, viral particles were seldom found in TEM photomicrograph thin sections of lysing K. brevis cells. Although a virus specific for K. brevis may have been the FLA, other explanations such as filterable bacteria or bacteriophages specific for bacteria associated with the K. brevis cultures cannot be discounted. [TOP OF PAGE]

  39. Spatial stability of bacterial and viral community compositions in Danish coastal waters as depicted by DNA fingerprinting techniques. Riemann,L., Middelboe,M. (2002). Aquat. Microb. Ecol. 27:219-232. [TOP OF PAGE]

  40. Viral lysis of marine bacterioplankton: Potential implications for organic matter cycling and bacterial clonal composition. Riemann,L., Middelboe,M. (2002). Ophelia 56:57-68. [TOP OF PAGE]

  41. Coccolithovirus (Phycodnaviridae): characterisation of a new large dsDNA algal virus that infects Emiliania huxleyi. Schroeder,D., Oke,J., Malin,G., Wilson,W.H. (2002). Arch Virol 147:1685-1698. Emiliania huxleyi-specific viruses (EhV) were isolated from E. huxleyi blooms off the coast of Plymouth, UK, in July 1999 and July/August 2001, and from an E. huxleyi bloom induced during a mesocosm experiment in a fjord off Bergen, Norway, during June 2000. Transmission electron microscopy revealed that all 10 virus isolates are 170-200 nm in diameter with an icosahedral symmetry. Their density is approximately 1.2 in CsCl gradients and they have large double stranded DNA genomes approximately 410 kb in size. Phylogenetic analysis of the DNA polymerase genes of these viruses suggests that EhV belongs to a new genus within the family of algal viruses, Phycodnaviridae. We propose to name this new virus genus Coccolithovirus. Differences within members of the Coccolithovirus were elucidated by host range analysis of the virus isolates and sequence analysis of a gene fragment encoding part of their putative major capsid protein. All 10 virus isolates within this new genus only infected E. huxleyi strains that have previously been shown to exhibit low dimethylsulphoniopropionate lyase (DMSP-lyase) activity (CCMP1516, CCMP374 and L), while E. huxleyi strains with high DMSP-lyase activity (CCMP373 and CCMP379) were resistant to infection. [TOP OF PAGE]

  42. Sequence analysis of marine virus communities reveals groups of related algal viruses are widely distributed in nature. Short,S.M., Suttle,C.A. (2002). Appl. Environ. Microbiol. 68:1290-1296. Algal-virus-specific PCR primers were used to amplify DNA polymerase (pol) gene fragments from geographically isolated natural virus communities. Natural algal virus communities were obtained from coastal sites in the Pacific Ocean in British Columbia, Canada, and the Southern Ocean near the Antarctic peninsula. Genetic fingerprints of algal virus communities were generated using denaturing gradient gel electrophoresis (DGGE). Sequencing efforts recovered 33 sequences from the gradient gel. Of the 33 sequences examined, 25 encoded a conserved amino acid motif indicating that the sequences were pol gene fragments. Furthermore, the 25 pol sequences were related to pol gene fragments from known algal viruses. In addition, similar virus sequences (>98% sequence identity) were recovered from British Columbia and Antarctica. Results from this study demonstrate that DGGE with degenerate primers can be used to qualitatively fingerprint and assess genetic diversity in specific subsets of natural virus communities and that closely related viruses occur in distant geographic locations. DGGE is a powerful tool for genetically fingerprinting natural virus communities and may be used to examine how specific components of virus communities respond to experimental manipulations. [TOP OF PAGE]

  43. [Physical mapping of DNA of cyanophage LPP-3]. Syrchin,S.A., Mendzhul,M.I. (2002). Mikrobiol. Zh. 64:24-30. Restrictases fit for the purposes of physical mapping of cyanophage LPP-3 DNA have been selected as a result of the restriction analysis. The use of the methods of mutual hydrolysis, restriction of the fragment isolated from gel and terminal labeling allowed formation a physical map of LPP-3 cyanophage DNA with the complete scheme of allocation of 14 sites for 8 restrictases: Alw44I, Bsp1191, BsuRI, Eco147I, EheI, NcoI, Kpn2I and PvuI as well as the position of certain sites for restrictases HindIII, KpnI and Sau3A. [TOP OF PAGE]

  44. [Some peculiarities of DNA structure of cyanophage LPP-3]. Syrchin,S.A., Mendzhul,M.I. (2002). Mikrobiol. Zh. 64:35-43. The efficiency of radioactive labeling of 3'- and 5'-ends of cyanophage LPP-3 DNA by polynucleotide kinase T4 and terminal transferase under various reaction conditions has been investigated. The obtained data prove that cyanophage LPP-3 DNA has the protruding 3'-ends. The experiments on ligation of native molecules of LPP-3 DNA evidence that the virus genome ends do not display any complimentarity. Separate fragments of LPP-3 DNA were cloned. The restriction analysis of the cloned fragments has confirmed a supposition on the absence of LPP-3 cyanophage of GGGCC and GGCCC sequences in the genome. A hypothesis has been suggested about similar site-specificity of the virus. Counterselection of the genome LPP-3 cyanophage allows it to be considered a promising one in the construction of new cloning vectors in cyanobacterium. [TOP OF PAGE]

  45. Reconsidering transmission electron microscopy based estimates of viral infection of bacterio-plankton using conversion factors derived from natural communities. Weinbauer,M.G., Winter,C., Hofle,M.G. (2002). Aquat. Microb. Ecol. 27:103-110. The frequency of virus infected bacterial cells (FIC) was estimated in surface waters of the Mediterranean Sea, the Baltic Sea and the North Sea using the frequency of visibly infected cells (FVIC) as determined by transmission electron microscopy (TEM) and published average conversion factors (average 5.42, range 3.7 to 7.14) to relate FVIC to FIC. A virus dilution approach was used to obtain an independent estimation of FIC in bacterioplankton, and we provide evidence for the reliability of this approach. Across all investigated environments, FIC ranged from 2.4 to 43.4 %. FIC data using both approaches were well correlated; however, the values were higher using the virus dilution approach, This indicates that the TEM approach has the potential to reveal spatiotemporal trends of viral infection; however, it may underestimate the significance of viral infection of bacteria when average conversion factors are used. Using data from the virus dilution approach and the TEM approach, we calculated new conversion factors for relating FVIC to FIC (average 7.11, range 4.34 to 10.78). Virally caused mortality of bacteria estimated from published FVIC data of marine and freshwater systems and using the new conversion factors ranged from not detectable to 129 %, thus confirming that viral infection is a significant and spatiotemporally variable cause of bacterial cell death. [TOP OF PAGE]

  46. Pseudoalteromonas spp. phages, a significant group of marine bacteriophages in the North Sea. Wichels,A., Gerdts,G., Schuett,C. (2002). Aquat. Microb. Ecol. 27:233-239. The occurrence and distribution of specific bacteriophages of marine Pseudoalteromonas spp. in the North Sea (North Sea phages) and their genetic relationship to several previously isolated marine phage species from waters of the Helgoland Roads (German Bight, Helgoland phages) were investigated. During 3 cruises from the Elbe estuary to western Norwegian waters, phages were concentrated by ultrafiltration. Detection and isolation of North Sea phages were performed by plaque assay, with 70 host bacteria of the genus Pseudoalteromonas. The genetic relationship between North Sea phages from different stations and Helgoland phages, formerly described as Pseudoalteromonas spp. phages, was assessed by DNA-DNA hybridization. DNA probes were prepared using whole phage DNA derived from 13 Helgoland phages. This approach provides the first information on the distribution of specific Pseudoalteromonas spp. phage-host systems (PHS) in the North Sea. The occurrence of Pseudoalteromonas spp. phages, which are specific for the tested Pseudoalteromonas spp. host bacteria, was restricted to a narrow geographical region of the German Bight between 53 degree 30' and 57 degree 00' N latitude. Most of the previously isolated Helgoland phages were highly host specific (54%), whereas this was true for only some of the 39 North Sea phages (16%). The most common Pseudoalteromonas spp. phage species found in the North Sea belong to the virus family Siphoviridae (species H103/1). Several phage strains within this phage species displayed different host sensitivity patterns. [TOP OF PAGE]

  47. Virus dynamics in a coccolithophore-dominated bloom in the North Sea. Wilson,W.H., Tarran,G., Zubkoy,M.V. (2002). Deep Sea Research Part II: Tropical Studies in Oceanography 49:2951-2963. We used analytical flow cytometry (AFC) to determine virus concentrations through vertical profiles in a coccolithophore-dominated bloom in the northern North Sea during June 1999. We present the first high-intensity sampling data of viruses from a lagrangian survey to gain a unique insight into the temporal and spatial dynamics of viruses in an open-water sight. Virus abundances ranged from 2.6×10(5) to 5.4×10(6)ml(-1), which is within the range expected for open-water environments. The highest concentrations were invariably observed in surface waters. During the lagrangian experiment there was a net decrease in virus numbers, suggesting that they were actively infecting hosts. Large viruses could be easily discriminated from small viruses since there was at least an order of magnitude difference in their AFC side-scatter values. Large viruses, assumed to infect DMS-producing algae, did not appear to influence DMS/DMSP production. It is likely that microzooplankton out-competed viruses for coccolithophore prey/hosts. Lower small virus to bacteria ratios (VBR) were observed in a subsurface layer compared to the more productive surface layers. The subsurface layer was dominated by a species of a-proteobacteria related to the genus Roseobacter, and the low VBR may indicate that viruses were infecting Roseobacter in this layer. Application of AFC is an excellent technique for high-definition sampling of virus communities, although it is recognised that we are working at the limit of detection for many small viruses using currently available nucleic acid stains. [TOP OF PAGE]

  48. Isolation of viruses responsible for the demise of an Emiliania huxleyi bloom in the English Channel. Wilson,W.H., Tarran,G.A., Schroeder,D., Cox,M., Oke,J., Malin,G. (2002). Journal of the Marine Biological Association of the UK 82:369-377. [TOP OF PAGE]

  49. Evolution of lambdoid replication modules. Wrobel,B., Wegrzyn,G. (2002). Virus Genes 24:163-171. Comparison of the putative iteron-binding proteins of lambdoid phages allows us to propose that in the case of lambdoid replication modules, the units on which natural selection acts do not coincide with the open reading frames. Rather, the first replication gene is split into two segments, and its 3' part (corresponding to the C-terminal domain of the iteron-binding protein) forms one unit with the second gene. We also propose from the phylogenetic analysis of phage-encoded homologs of E. coli DnaB and DnaC, that the recombination with the host sequences is not frequent. Accessory ATP-ases for helicase loading (E. coli DnaC homologs) may not be universal replication proteins. Our analysis may suggest that the bacterial helicase loaders might be of phage origin. The comparison of DnaC homologs of enterobacteria and enterobacterial phages supports the experimental data on residues important in interaction with DnaB. We propose that construction of plasmids carrying the replication origins of lambdoid prophages could be useful not only in further research on DNA replication but also on the role of these prophages in shuttling genes for bacterial virulence. The phage replication sequences could be also useful for identification of clinical enterobacterial isolates. [TOP OF PAGE]

  50. Phylogenetic diversity of marine cyanophage isolates and natural virus communities as revealed by sequences of viral capsid assembly protein gene g20. Zhong,Y., Chen,F., Wilhelm,S.W., Poorvin,L., Hodson,R.E. (2002). Appl. Environ. Microbiol. 68:1576-1584. In order to characterize the genetic diversity and phylogenetic affiliations of marine cyanophage isolates and natural cyanophage assemblages, oligonucleotide primers CPS1 and CPS8 were designed to specifically amplify ca. 592-bp fragments of the gene for viral capsid assembly protein g20. Phylogenetic analysis of isolated cyanophages revealed that the marine cyanophages were highly diverse yet more closely related to each other than to enteric coliphage T4. Genetically related marine cyanophage isolates were widely distributed without significant geographic segregation (i.e., no correlation between genetic variation and geographic distance). Cloning and sequencing analysis of six natural virus concentrates from estuarine and oligotrophic offshore environments revealed nine phylogenetic groups in a total of 114 different g20 homologs, with up to six clusters and 29 genotypes encountered in a single sample. The composition and structure of natural cyanophage communities in the estuary and open-ocean samples were different from each other, with unique phylogenetic clusters found for each environment. Changes in clonal diversity were also observed from the surface waters to the deep chlorophyll maximum layer in the open ocean. Only three clusters contained known cyanophage isolates, while the identities of the other six clusters remain unknown. Whether or not these unidentified groups are composed of bacteriophages that infect different Synechococcus groups or other closely related cyanobacteria remains to be determined. The high genetic diversity of marine cyanophage assemblages revealed by the g20 sequences suggests that marine viruses can potentially play important roles in regulating microbial genetic diversity. [TOP OF PAGE]

  51. Distribution of virus-like particles in an oligotrophic marine environment (Alboran Sea, Western Mediterranean). Alonso,M.C., Jimenez-Gomez,F., Rodriguez,J., Borrego,J.J. (2001). Microb. Ecol. 42:407-415. Viruses are abundant in a variety of aquatic environments, often exceeding bacterial abundance by one order of magnitude. In the present study, the spatial distribution of viruses in offshore waters of the Alboran Sea (Western Mediterranean) have been studied to determine the relationships between viruses and host communities in this oligotrophic marine environment. Viral abundance was determined using two methods: (i) epifluorescence light microscopy using the dsDNA binding fluorochrome DAPI, and (ii) direct counts by transmission electron microscopy (TEM). The results obtained were significantly different; the highest viral counts were obtained by mean of TEM analyses. In all the samples tested the number of viruses was exceeded by the bacterial concentrations, with a ratio between viral and bacterial titers varying between 1.4 and 20. VLP (virus-like particle) counts were not significantly correlated (p>0.001) with chlorophyll a concentration or the abundance of cyanobacteria. However, there was a positive and significant correlation with bacterial abundance (p<0.001). The analysis of size and morphology of viral particles by TEM and the correlation obtained between the numbers of VLP and bacteria suggest that the majority of the viral particles in the Alboran Sea are bacteriophages. None of the indirect evidence suggested that eukaryotic algae or cyanobacteria were important host organisms in these waters. [TOP OF PAGE]

  52. Microbial population dynamics and diversity during a bloom of the marine coccolithophorid Emiliania huxleyi (Haptophyta). Castberg,T., Larsen,A., Sandaa,R.A., Brussaard,C.P.D., Egge,J.K., Heldal,M., Thyrhaug,R., van Hannen,E.J., Bratbak,G. (2001). Mar. Ecol. Prog. Ser. 221:39-46. Several previous studies have shown that Emiliania huxleyi blooms and terminations have been succeeded by an increase in large virus-like particles (LVLP), strongly suggesting the bloom collapse was caused by viral lysis. However, due to methodological limitations, knowledge of how such blooms affect the rest of the microbial community is limited. In the current study we induced a bloom of E. huxleyi in seawater enclosures and applied methods enabling us to describe the algae, bacteria and virus communities with greater resolution than has been done previously, The development of the dominating algal, viral and bacterial populations in the nutrient-amended seawater enclosures was followed by flow cytometry (FCM). Light microscopy (LM), PCR-denaturing gradient gel electrophoresis (PCR-DGGE) and pulsed-field gel electrophoresis (PFGE) were used to describe the changes in community composition in greater detail. The algal community was dominated by E. huxleyi until termination of the bloom by viral lysis, After bloom termination the additional algal populations present in the enclosures increased in abundance. A marked increase in viruses other than the one infecting E. huxleyi was also observed. Total bacterial number and community composition were also greatly influenced by the bloom and its collapse. [TOP OF PAGE]

  53. Use of octyl beta-thioglucopyranoside in two-dimensional crystallization of membrane proteins. Chami,M., Pehau-Arnaudet,G., Lambert,O., Ranck,J.L., Levy,D., Rigaud,J.L. (2001). J Struct Biol 133:64-74. A great interest exists in producing and/or improving two-dimensional (2D) crystals of membrane proteins amenable to structural analysis by electron crystallography. Here we report on the use of the detergent n-octyl beta-d-thioglucopyranoside in 2D crystallization trials of membrane proteins with radically different structures including FhuA from the outer membrane of Escherichia coli, light-harvesting complex II from Rubrivivax gelatinosus, and Photosystem I from cyanobacterium Synechococcus sp. We have analyzed by electron microscopy the structures reconstituted after detergent removal from lipid-detergent or lipid-protein-detergent micellar solutions containing either only n-octyl beta-d-thioglucopyranoside or n-octyl beta-d-thioglucopyranoside in combination with other detergents commonly used in membrane protein biochemistry. This allowed the definition of experimental conditions in which the use of n-octyl beta-d-thioglucopyranoside could induce a considerable increase in the size of reconstituted membrane structures, up to several micrometers. An other important feature was that, in addition to reconstitution of membrane proteins into large bilayered structures, this thioglycosylated detergent also was revealed to be efficient in crystallization trials, allowing the proteins to be analyzed in large coherent two-dimensional arrays. Thus, inclusion of n-octyl beta-d-thioglucopyranoside in 2D crystallization trials appears to be a promising method for the production of large and coherent 2D crystals that will be valuable for structural analysis by electron crystallography and atomic force microscopy. [TOP OF PAGE]

  54. Application of digital image analysis and flow cytometry to enumerate marine viruses stained with SYBR gold. Chen,F., Lu,J.R., Binder,B.J., Liu,Y.C., Hodson,R.E. (2001). Appl. Environ. Microbiol. 67:539-545. A novel nucleic acid stain, SYBR Gold, was used to stain marine viral particles in various types of samples. Viral particles stained with SYBR Gold yielded bright and stable fluorescent signals that could be detected by a cooled charge-coupled device camera or by flow cytometry. The fluorescent signal strength of SYBR Gold-stained viruses was about twice that of SYBR Green I-stained viruses. Digital images of SYBR Gold-stained viral particles were processed to enumerate the concentration of viral particles by using digital image analysis software. Estimates of viral concentration based on digitized images were 1.3 times higher than those based on direct counting by epifluorescence microscopy. Direct epifluorescence counts of SYBR Gold-stained viral particles were in turn about 1.34 times higher than those estimated by the transmission electron microscope method. Bacteriophage lysates stained with SYBR Gold formed a distinct population in flow cytometric signatures. Flow cytometric analysis revealed at least four viral subpopulations for a Lake Erie sample and two subpopulations for a Georgia coastal sample. Flow cytometry-based viral counts for various types of samples averaged 1.1 times higher than direct epifluorescence microscopic counts. The potential application of digital image analysis and flow cytometry for rapid and accurate measurement of viral abundance in aquatic environments is discussed. [TOP OF PAGE]

  55. A conserved genetic module that encodes the major virion components in both the coliphage T4 and the marine cyanophage S-PM2. Hambly,E., Tétart,F., Desplats,C., Wilson,W.H., Krisch,H.M., Mann,N.H. (2001). Proc. Natl. Acad. Sci. USA 98:11411-11416. Sequence analysis of a 10-kb region of the genome of the marine cyanomyovirus S-PM2 reveals a homology to coliphage T4 that extends as a contiguous block from gene (g)18 to g23. The order of the S-PM2 genes in this region is similar to that of T4, but there are insertions and deletions of small ORFs of unknown function. In T4, g18 codes for the tail sheath, g19, the tail tube, g20, the head portal protein, g21, the prohead core protein, g22, a scaffolding protein, and g23, the major capsid protein. Thus, the entire module that determines the structural components of the phage head and contractile tail is conserved between T4 and this cyanophage. The significant differences in the morphology of these phages must reflect the considerable divergence of the amino acid sequence of their homologous virion proteins, which uniformly exceeds 50%. We suggest that their enormous diversity in the sea could be a result of genetic shuffling between disparate phages mediated by such commonly shared modules. These conserved sequences could facilitate genetic exchange by providing partially homologous substrates for recombination between otherwise divergent phage genomes. Such a mechanism would thus expand the pool of phage genes accessible by recombination to all those phages that share common modules. [TOP OF PAGE]

  56. Effects of concentrated viral communities on photosynthesis and community composition of co-occurring benthic microalgae and phytoplankton. Hewson,I., O'Neil,J.M., Heil,C.A., Bratbak,G., Dennison,W.C. (2001). Aquat. Microb. Ecol. 25:1-10. Marine viruses have been shown to affect phytoplankton productivity; however, there are no reports on the effect of viruses on benthic microalgae (microphytobenthos). Hence, this study investigated the effects of elevated concentrations of virus-like particles on the photosynthetic physiology and community composition of benthic microalgae and phytoplankton. Virus populations were collected near the sediment surface and concentrated by tangential flow ultrafiltration, and the concentrate was added to benthic and water column samples that were obtained along a eutrophication gradient in the Brisbane River/Moreton Bay estuary, Australia. Photosynthetic and community responses of benthic microalgae, phytoplankton and bacteria were monitored over 7 d in aquaria and in situ. Benthic microalgal communities responded to viral enrichment in both eutrophic and oligotrophic sediments. In eutrophic sediments, Euglenophytes (Euglena sp.) and bacteria decreased in abundance by 20 to 60 and 26 to 66%, respectively, from seawater controls. In oligotrophic sediments, bacteria decreased in abundance by 30 to 42% from seawater controls but the dinoflagellate Gymnodinium sp. increased in abundance by 270 to 3600% from seawater controls, The increased abundance of Gymnodinium sp. may be related to increased availability of dissolved organic matter released from lysed bacteria. Increased (140 to 190% from seawater controls) initial chlorophyll a fluorescence measured with a pulse-amplitude modulated fluorometer was observed in eutrophic benthic microalgal incubations following virus enrichment, consistent with photosystem II damage. Virus enrichment in oligotrophic water significantly stimulated carbon fixation rates, perhaps due to increased nutrient availability by bacterial lysis. The interpretation of data from virus amendment experiments is difficult due to potential interaction with unidentified bioactive compounds within seawater concentrates. However, these results show that viruses are capable of influencing microbial dynamics in sediments. [TOP OF PAGE]

  57. Virus-like particle distribution and abundance in sediments and overlying waters along eutrophication gradients in two subtropical estuaries. Hewson,I., O'Neil,J.M., Fuhrman,J.A., Dennison,W.C. (2001). Limnol. Oceanogr. 46:1734-1746. Viruses are recognized as ubiquitous components of marine ecosystems; however, there has been limited study of viral abundance and its ecological role in sediments. Viral abundance was determined in both the water column and sediments of a eutrophic (Brisbane River/Moreton Bay; 27º25'S, 153º5'E) and oligotrophic (Noosa River; 26º15'S, 153º0'E) estuary in subtropical Queensland, Australia. Viruses, bacteria, and microalgae from both water column and extracted sediment samples were enumerated using SYBR Green I staining and epifluorescence microscopy. Sediment viral abundance ranged from 107 to 109 particles cm-3 of sediment, bacterial abundance ranged from 107 to 108 cells cm-3 of sediment, and microalgal abundance ranged from 104 to 105 cells cm-3 sediment. Pelagic abundances for all microorganisms were 10-1,000-fold lower than sediment abundances. Correlations between viral abundances and suspended solids suggest that viruses sorbed to suspended material in the water column may settle out and contribute to the benthic viral population. Virus production was measured by a time course increase of viral abundance in seawater using a dilution technique. Virus production was highest in eutrophic waters of the Brisbane River, and addition of inorganic nutrients (NO3- + NH4+ + PO4-3 + SiO3) stimulated viral production rates at all stations by 14-52% above ambient, suggesting that inorganic nutrient availability may play a key role in aquatic viral abundance. [TOP OF PAGE]

  58. Seasonal dynamics of viruses in an alpine lake: Importance of filamentous forms. Hofer,J.S., Sommaruga,R. (2001). Aquat. Microb. Ecol. 26:1-11. Viruses are an important component of the planktonic food web in freshwater and marine systems, but most studies have been done in the ocean and in lowland lakes. In this work, the seasonal dynamics and structure of the virioplankton as well as their impact on bacteria during a day/night cycle were studied in an alpine lake located 2417 m above sea level. The abundance of virus-like particles (VLP) was determined at 5 discrete depths (0.5 to 8 m) by direct counts with a TEM in samples collected from May to November 1998 at weekly to bi-weekly intervals. Viruses reached the highest abundances under ice (4.6 X 106 VLP ml-1) with a second maximum in autumn. After ice-break, the VLP abundance decreased to undetectable values (<2 X 104 VLP ml-1) probably because of the negative effect of solar radiation that was negatively correlated with the viral abundance in the upper 2 m of the water column (Spearman rank correlation, rs = -0.773, p < 0.01). The virioplankton was morphologically diverse, consisting of forms commonly found in other aquatic systems, but unlike other studies, we found filamentous VLP (FVLP) 450 to 730 nm long that attained abundances of up to 1.3 X 106 ml-1 and accounted for 7 to 100% of the total viral abundance. These FVLP were found occasionally inside filamentous heterotrophic bacteria (> 10 mum) and their respective abundances were positively correlated (rs = 0.728, p < 0.01). The absence of these conspicuous forms in other aquatic ecosystems suggests that FVLP are well adapted to the harsh environmental conditions or are specific to bacterial hosts found in alpine lakes. Finally, between 5 and 28% of the newly produced bacteria were killed by non-filamentous viruses, which therefore are a modest cause of bacterial mortality in this lake. [TOP OF PAGE]

  59. The chaperonins of Synechocystis PCC 6803 differ in heat inducibility and chaperone activity. Kovacs,E., van der Vies,S.M., Glatz,A., Torok,Z., Varvasovszki,V., Horvath,I., Vigh,L. (2001). Biochem Biophys Res Commun 289:908-915. The chaperonins GroEL and Cpn60 were isolated from the cyanobacterium Synechocystis PCC 6803 and characterized. In cells grown under optimal conditions their ratio was about one to one. However, the amount of GroEL increased considerably more than that of Cpn60 in response to heat stress. The labile chaperonin oligomer required stabilization by MgATP or glycerol during isolation. Use of the E. coli mutant strain, groEL44 revealed that the functional properties of the two cyanobacterial chaperonins are strikingly different. Overexpression of cyanobacterial GroEL in the E. coli mutant strain allowed growth at elevated temperature, the formation of mature bacteriophage T4, and active Rubisco enzyme assembly. In contrast, Cpn60 partially complemented the temperature-sensitive phenotype, the Rubisco assembly defect and did not promote the growth of the bacteriophage T4. The difference in chaperone activity of the two cyanobacterial chaperonins very probably reflects the unique chaperonin properties required during the life of Synechocystis PCC 6803. [TOP OF PAGE]

  60. Population dynamics and diversity of phytoplankton, bacteria and viruses in a seawater enclosure. Larsen,A., Castberg,T., Sandaa,R.A., Brussaard,C.P.D., Egge,J.K., Heldal,M., Paulino,A., Thyrhaug,R., van Hannen,E.J., Bratbak,G. (2001). Mar. Ecol. Prog. Ser. 221:47-57. We now know that the abundance of free viruses in most marine environments is high. There is still, however, a lack of understanding of their occurrence and distribution and of in situ relationships between viral and host communities in natural environments. This may be partly due to methodological limitations. Our main aim was therefore to perform a case study in which a variety of methods were applied in order to give an improved, high-resolution description of the microbial communities in a natural environment, In order to do this we combined light microscopy (LM), transmission electron microscopy (TEM), flow cytometry (FCM), PCR denaturing gradient gel electrophoresis (PCR-DGGE) and pulsed-field gel electrophoresis (PFGE) and studied the diversity and succession of algae, bacteria and viruses in a nutrient enriched seawater enclosure. In the enclosure we experienced a situation where the development of the dominating algal population, which consisted of several flagellate species, was followed by proliferation of several different size-classes of viruses. The total bacterial number decreased markedly during the flagellate bloom but the community composition was maintained and the diversity remained high. Our results indicate a close linkage between various algal, bacterial and viral populations and show that virioplankton do not necessarily terminate algal and bacterial blooms but that they keep the host populations at non-blooming levels. [TOP OF PAGE]

  61. A novel virus (HaNIV) causes lysis of the toxic bloom-forming alga Heterosigma akashiwo (Raphidophyceae). Lawrence,J.E., Chan,A.M., Suttle,C.A. (2001). J. Phycol. 37:216-222. We describe a previously unknown virus that causes lysis of the toxic blopm-forming alga Heterosigma akashiwo (Hada) Hara et Chihara (Raphidophyceae). Heterosigma akashiwo nuclear inclusion virus (HaNIV) does not resemble other algal viruses described to date. HaNIV is small (ca. 30 nm diameter), is assembled in the nucleus, and forms crystalline arrays. We estimate that approximately 105 HaNIV particles are released during lysis of a cell. During a time-course experiment, TEM revealed the first signs of HaNIV infection 24 h after viral addition, and by 74 h 98% of observed cells were visibly infected. The onset of cell lysis, as indicated by a decrease in the relative fluorescence of the cultures, was apparent by 42 h postinfection. The heterochromatin of infected cells is frequently found at the margin of the nucleoplasm, which is consistent with virus-mediated programmed cell death, or apoptosis. HaNIV is clearly different from other described viruses that infect alg ae, including other viral pathogens of H, akashiwo. These results indicate that viruses other than Phycodnaviridae are pathogens and cause mortality of microalgae in marine systems. It is Likely that HaNIV plays an integral role in the population dynamics of H. akashiwo. [TOP OF PAGE]

  62. Viruses in the plankton of freshwater and saline Antarctic lakes. Laybourn-Parry,J., Hofer,J.S., Sommaruga,R. (2001). Freshwater Biology 46:1279-1287. 1. Virus-like particle (VLP) abundances in nine freshwater to saline lakes in the Vestfold Hills, Eastern Antarctica (68degree S) were determined in December 1999. In the ultra-oligotrophic to oligotrophic freshwater lakes, VLP abundances ranged from 1.01 to 3.28 X 106 mL-1 in the top 6 m of the water column. In the saline lakes the range was between 6.76 and 36.5 X 106 mL-1. The lowest value was found in meromictic Ace Lake and the highest value in hypersaline Lake Williams. Virus to bacteria ratios (VBR) were lowest in the freshwater lakes and highest in the saline lakes, with a maximum of 23.4 in the former and 50.3 in the latter. 2. A range of morphologies among VLP was observed, including phages with short (Podoviridae) and long tails, icosahedric viruses of up to 300 nm and star-like particles of about 80 nm diameter. 3. In these microbially dominated ecosystems there was no correlation between VLP and either bacterial numbers of chlorophyll a. There was a significant correlation between VLP abundances and dissolved organic carbon concentration (r = 0.845, P < 0.01). 4. The data suggested that viruses probably attack a spectrum of bacteria and protozoan species. Virus-like particle numbers in the freshwater lakes were lower than values reported for lower latitude systems. Those in the saline lakes were comparable with abundances reported from other Antarctic lakes, and were higher than most values published for lower latitude lakes and many marine systems. Across the salinity spectrum from freshwater through brackish to hypersaline, VLP concentrations increased roughly in relation to increasing trophy. 5. Given that Antarctic lakes have a plankton almost entirely made up of bacteria and protists, and that VLP abundances are high, it is likely that viruses play a pivotal role in carbon cycling in these extreme ecosystems. [TOP OF PAGE]

  63. Distribution, isolation, host specificity, and diversity of cyanophages infecting marine Synechococcus spp. in river estuaries. Lu,J., Chen,F., Hodson,R.E. (2001). Appl. Environ. Microbiol. 67:3285-3290. The abundance of cyanophages infecting marine Synechococcus spp. increased with increasing salinity in three Georgia coastal rivers. About 80% of the cyanophage isolates were cyanomyoviruses. High cross-infectivity was found among the cyanophages infecting phycoerythrin-containing Synechococcus strains. Cyanophages in the river estuaries were diverse in terms of their morphotypes and genotypes. [TOP OF PAGE]

  64. Turning the phage on produce pathogens. McBride,J. (2001). Agricultural Research 2001(July), 12. Even bacteria have their nemesis. Tiny viruses, called phages, infect and kill bacteria naturally, including the foodborne pathogens that sometimes make humans so sick, they wish they were dead. ¶ So why not put these phages to work on fresh-cut fruit, thought ARS plant pathologists Britta Leverentz and William S. Conway at the Produce Quality and Safety Laboratory in Beltsville, Maryland. ¶ Since phages home in on a bacterium's surface proteins, they are very selective about their hosts. Phages specific for Salmonella, for instance, would leave beneficial bacteria free to multiply on fresh-cut produce and crowd out potential pathogens, Leverentz explains. ¶ What's more, these tiny viruses are natural, safe, and ubiquitous. A small dropperful of fresh water from a stream or lake, for example, contains an average 250 million phages. Before antibiotics, phages were used to treat human infections in the United States and are still used therapeutically in other parts of the world. ¶ Phages are already under study to control pathogens in poultry, meat, and eggs. Leverentz and Conway are the first to investigate their potential to reduce pathogens on fruits and vegetables— both whole and fresh-cut. They are working under a cooperative research and development agreement with Intralytix in Baltimore, Maryland, which is providing known phages for Salmonella Enteritidis. A patent application has been filed on the use of phages with produce. [TOP OF PAGE]

  65. Effects of bacteriophages on the population dynamics of four strains of pelagic marine bacteria. Middelboe,M., Hagstrom,A., Blackburn,N., Sinn,B., Fischer,U., Borch,N.H., Pinhassi,J., Simu,K., Lorenz,M.G. (2001). Microb. Ecol. 42:395-406. Viral lysis of specific bacterial populations has been suggested to be an important factor for structuring marine bacterioplankton communities. In the present study, the influence of bacteriophages on the diversity and population dynamics of four marine bacterial phage-host systems was studied experimentally in continuous cultures and theoretically by a mathematical model. By use of whole genome DNA hybridization toward community DNA, we analyzed the dynamics of individual bacterial host populations in response to the addition of their specific phage in continuous cultures of mixed bacterial assemblages. In these experiments, viral lysis had only temporary effects on the dynamics and diversity of the individual bacterial host species. Following the initial lysis of sensitive host cells, growth of phage-resistant clones of the added bacteria resulted in a distribution of bacterial strains in the phage-enriched culture that was similar to that in the control culture without phages after about 50-60 h incubation. Consequently, after a time frame of 5-10 generations after lysis, it was the interspecies competition rather than viral lysis of specific bacterial strains that was the driving force in the regulation of bacterial species composition in these experiments. The clonal diversity, on the other hand, was strongly influenced by viral activity, since the clonal composition of the four species in the phage-enriched culture changed completely from phage-sensitive to phage-resistant clones. The model simulation predicted that viral lysis had a strong impact on the population dynamics, the species composition, and the clonal composition of the bacterial community over longer time scales (weeks). However, according to the model, the overall density of bacteria in the system was not affected by phages, since resistant clones complemented the fluctuations caused by viral lysis. Based on the model analysis, we therefore suggest that viral lysis can have a strong influence on the dynamics of bacterial populations in planktonic marine systems. [TOP OF PAGE]

  66. Environmental bacteriophage-host interactions: Factors contribution to natural transduction. Miller,R.V. (2001). Antonie van Leeuwenhoek 79:141-147. Over the past two decades the potential for the exchange of bacterial genes in natural environments through transduction (bacteriophage-mediated gene transfer) has been well established. Studies carried out by various laboratories throughout the world have demonstrated that both chromosomal and plasmid DNA can be successfully transduced in natural environments ranging from sewer plants to rivers and lakes. Transduction has been shown to take place in the gills of oysters and the kidneys of mice. Model studies have demonstrated the ability of transduction to maintain genetic material in bacterial gene pools that would otherwise be lost because of negative fitness. Thus, transduction may affect the course of bacterial evolution. Identification of natural transduction has led to the investigation of the dynamics of bacteriophage host interactions in natural aquatic environments and to the exploration of various environmental factors that affect virus-host interactions. Two important environmental factors which affect virus-host interactions are the metabolic state of the host and the exposure of the host to DNA-damaging stresses such as solar UV light. Recent researches on these two areas of virus-host relationships are reviewed. [TOP OF PAGE]

  67. Validity of Escherichia coli, enterovirus, and F-specific RNA bacteriophages as indicators of viral shellfish contamination. Miossec,L., Le Guyader,F., Pelletier,D., Haugarreau,L., Caprais,M.P., Pommepuy,M. (2001). J. Shelfish Res. 20:1223-1227. The sanitary classification of harvesting areas for bivalve mollusks in France is based on the level of Escherichia coli contamination detected in shellfish meat, as defined in EC Directive 91/492 EEC. However, outbreaks of gastroenteritis or hepatitis after consumption of shellfish meeting current bacteriological standards suggest that E. coli is a poor indicator of viral contamination. The purpose of this study was to assess the adequacy of enterovirus and F-specific RNA bacteriophages as new indicators of human enteric viruses. Shellfish were sampled over a 37-mo period to characterize microbial contamination in two coastal areas subjected to different sewage contamination inputs. Contamination by E. coli, F-specific RNA bacteriophages (F+ RNA) and human enteric viruses (enterovirus, EV; hepatitis A virus, HAV; Norwalk-like virus, NLV; astrovirus, AV; and rotavirus, RV) was measured in the same samples. E. coli analysis was performed by conductance measurement, enteric viruses were detected by reverse-transcription polymerase chain reaction (RT-PCR) and hybridization, and F+ RNA was evaluated by culture according to the ISO 10705-1 method. Statistical analysis based on bootstrap methods was performed on 95 series of paired observations. The validity of E. coli, enterovirus, and F-specific RNA bacteriophages as viral indicators was evaluated by measuring their sensitivity and specificity in the presence of enteric viruses. None of the tested indicators proved adequate to protect the public from viral shellfish contamination. The sensitivity of all indicators was better in the highly contaminated zone, and enteroviruses showed the highest specificity for both sites. [TOP OF PAGE]

  68. Estimating viral proliferation in aquatic samples. Noble,R., Steward,G. (2001). Methods in Mcirobiology 30:67-84. It is only within the last decade that marine viruses were determined to be consistently the most abundant biological entities in the sea (Fuhrman, 1999). Since then, many advances have been made in understanding viral ecology (Fuhrman, 1999, Wilhelm and Suttle, 1999). Initial discoveries showed that viruses are both abundant in the ocean and that many bacteria are infected with viruses (Bergh et al., 1989; Proctor and Fuhrman, 1990). These data led researchers to believe that viruses are an important source of mortality in marine microbial food webs, but only provided a static picture. Subsequent studies have shown that virus populations are extremely dynamic, and can change quickly over short time scales (Bratbak et al 1990, 1996). Estimates of viral production and decay rates provided the valuable confirmation that viruses are active members of the marine community (Heldal and Bratbak, 1991; Steward et al., 1992b). The production of viruses implies the lysis of host cells and the release of cellular material as dissolved and colloidal organic carbon. Therefore, measurements of viral replication rates are also useful for assessing the contribution of viruses to bacterial mortality and organic matter cycling in the ocean. By assuming a burst size, viral productivity can be used to estimate rates of bacterial lysis. This approach provides an additional means to assess bacterial mortality along with the original electron microscopy-based method of Proctor and Fuhrman (1990). Accurate measurements of viral productivity and turnover are required if we are to properly model their dynamics and impact within the microbial food web. So far, however, there is no standard method for measuring viral productivity. A wide variety of different approaches have been used each with associated advantages and disadvantages. These methods include:
    1. Quantifying net increases in viral abundance over time (Bratbak et al., 1990)
    2. Measuring rates of viral decay (Heldal and Bratbak, 1991)
    3. Estimating viral DNA synthesis rates by radiolabeling (Steward et al., 1992a,b)
    4. Calculating expected viral release rates from estimated rates of bacterial lysis and an assumed burst size (Weinbauer et al., 1993)
    5. Measuring tracer dilution rates using fluorescently labeled viruses (FLV) as tracers (Noble and Fuhrman, submitted)
    The first approach, observing net increases in viruses over time, is the simplest means of demonstrating viral proliferation. However, use of this method is restricted to times when viral abundance is increasing and only provides a minimum estimate of productivity unless the viral decay rate is also known. The productivity estimates obtained are also dramatically influenced by the time scale of sampling (Bratbak et al., 1994, 1996). In the second approach, virus production is prevented by poisoning or removing host organisms and the rate at which viruses disappear (or decay) is observed. If the system was initially in steady state, the decay rate is assumed equal to the original rate of production. These two approaches have been used in a number of studies and variations on them are possible. Due to space limitations, however, this chapter focuses only on the last three methods listed above. [TOP OF PAGE]

  69. Fingerprinting viral assemblages by pulsed field gel electrophoresis. Steward,G.F. (2001). pp. 85-102. In In Paul,J.H. (ed.), Marine Microbiology. Academic Press, London. Viruses are the most abundant microorganisms in marine and freshwater environments and perhaps the most genetically diverse (Fuhrman and Suttle, 1993). Counting viruses in aquatic samples is now a routine matter, but assessing the diversity and dynamics within complex assemblages is still a challenge. DNA-based fingerprinting approaches which rely on amplification of rRNA gene fragments by PCR have facilitated analyses of bacterial community composition. These approaches have more restricted application when analyzing viral assemblages, because of the extreme genetic diversity among viruses. Unlike in bacteria, there are no gene sequences conserved in all viruses which can serve as universal primer sites for PCR amplification. PCR-based analyses of viral assemblages must therefore target specific subsets of the total viral assemblage. For example, PCR amplification of specific genes has recently been used to examine the genetic diversity among cyanophages (Fuller et al., 1998) and among phycodnaviridae (Chen et al., 1996; Short and Suttle, 1999). A more general fingerprinting approach, which encompasses the total viral assemblage, is a valuable complement to these more specific, higher resolution analyses. The approach described here uses variation in genome size as the basis for obtaining a fingerprint of a viral assemblage (Klieve and Swain, 1993). A whole genome fingerprinting approach is possible, because viral genomes can vary greatly in length (a few thousand to hundreds of thousands of base pairs) yet they fall within a range that is easily resolved using pulsed field gel electrophoresis (PFGE). The PFGE fingerprinting technique provides a quick and relatively simple means of visualizing differences in the composition of viral assemblages (Swain et al., 1996; Wommack et al., 1999a; Steward and Azam, 2000). As a supplement to the more specific treatment of PFGE provided in this chapter, the reader is encouraged to consult the excellent introductory text to PFGE by Birren and Lai (1993). [TOP OF PAGE]

  70. Filamentous phage biology. Occurrence of coliphages in fish and aquaculture farms. Webster,R., Barbas,C.F., III, Burton,D.R., Scott,J.K., Silverman,G.J., Rao,B.M., Surendran,P.K. (2001). Fishery Technology 37:146-149. Coliphages were detected in water samples collected from brackish water and fresh water fish farms. Coliphages were also detected in the farmed fresh water fish, common carp and marine fish, oil sardine, from local market. Coliphage levels obtained were as follows:- water from brackish water fish farm 3, water from fresh water fish farm 23, fresh water fish 240 pfu.g-1 and marine fish 3500 pfu.g-1. [TOP OF PAGE]

  71. Interaction of the FHSIC virus with its host: lysogeny or pseudolysogeny? Williamson,S.J., McLaughlin,M.R., Paul,J.H. (2001). Appl. Environ. Microbiol. 67:1682-1688. The marine phage PhiHSIC has been previously reported to enter into a lysogenic relationship with its host, HSIC, identified as Listonella pelagia. This phage produces a variety of plaques on its host, including turbid and haloed plaques, from which lysogens were previously isolated. These lysogens were unstable during long-term storage at -80° C and were lost. When HSIC was reinfected with phage PhiHSIC, pseudolysogen-like interactions between the phage and its host were observed. The cells (termed HSIC-2 or HSIC-2e) produced high viral titers (1011 ml-1) in the absence of inoculating phage and yet reached culture densities of nearly 109 ml-1. Prophages were not induced by mitomycin C or the polyaromatic hydrocarbon naphthalene in cells harboring such infections. However, such cells were homoimmune to superinfection. Colonies hybridized strongly with a gene probe from a 100-bp fragment of the PhiHSIC genome, while the host did not. Analysis of chromosomal DNA preparations suggested the presence of a chromosomally integrated prophage. Phage adsorption experiments suggested that HSIC-2 was adsorption impaired. Because of the chromosomal prophage integration and homoimmunity, we interpret these results to indicate that PhiHSIC establishes a lysogenic relationship with its host that involves an extremely high level of spontaneous induction. This could be caused by a weak repressor of phage production. Additionally, poor phage adsorption of HSIC-2 compared to the wild type probably helped maintain this pseudolysogen-like relationship. In many ways, pseudolysogenic phage-host interactions may provide a paradigm for phage-host interactions in the marine environment. [TOP OF PAGE]

  72. Bacteriophage lambda and plasmid pUR288 transgenic fish models for detecting in vivo mutations. Winn,R.N., Norris,M., Muller,S., Torres,C., Brayer,K. (2001). Marine Biotechnology 3:185-195. We adapted transgenic rodent mutation assays based on fish carrying bacteriophage lambda and plasmid pUR288 vectors to address the needs for improved methods to assess health risks from exposure to environmental mutagens and also to establish new animal models to study in vivo mutagenesis. The approach entails separating the vectors from fish genomic DNA and then shuttling them into specialized strains of E. coli bacteria to analyze spontaneous and induced mutations in either lacI and cII or lacZ mutational targets. Fish exhibited low frequencies of spontaneous mutants comparable to the sensitivity of transgenic rodent models. Mutations detected after treating fish with chemical mutagens showed concentration-dependent, tissue-specific, and time-dependent relationships. Spontaneous and induced mutational spectra also were consistent with the specificity of known mutagens, further supporting the utility of transgenic fish for studies of in vivo mutagenesis. [TOP OF PAGE]

  73. Dynamic bacterial and viral response to an algal bloom at subzero temperatures. Yager,P.L., Connelly,T.L., Mortazavi,B., Wommack,K.E., Bano,N., Bauer,J.E., Opsahl,S., Hollibaugh,J.T. (2001). Limnol. Oceanogr. 46:790-801. New evidence suggests that cold-loving (psychrophilic) bacteria may be a dynamic component of the episodic bloom events of high-latitude ecosystems. Here we report the results of an unusually early springtime study of pelagic microbial activity in the coastal Alaskan Arctic. Heterotrophic bacterioplankton clearly responded to an algal bloom by doubling cell size, increasing the fraction of actively respiring cells (up to an unprecedented 84% metabolically active using redox dye CTC), shifting substrate-uptake capabilities from kinetic parameters better adapted to lower substrate concentrations to those more suited for higher concentrations, and more than doubling cell abundance. Community composition (determined by polymerase chain reaction/DGGE and nucleotide sequence analysis) also shifted over the bloom. Results support, for the first time with modern molecular methods, previous culture-based observations of bacterial community succession during Arctic algal blooms and confirm that previously observed variability in pelagic microbial activity can be linked to changes in community structure. During early bloom stages, virioplankton and bacterial abundance were comparable, suggesting that mortality due to phage infection was low at that time. The virus-to-bacteria ratio (VBR) increased 10-fold at the height of the bloom, however, suggesting an increased potential for bacterioplankton mortality resulting from viral infection. The peak in VBR coincided with observed shifts in both microbial activity and community structure. These early-season data suggest that substrate and virioplankton interactions may control the active microbial carbon cycling of this region. [TOP OF PAGE]

  74. Symposium on Harmful Marine Algae in the U.S. Anonymous (2000). [TOP OF PAGE]

  75. Role of ciliates, flagellates and bacteriophages on the mortality of marine bacteria and on dissolved-DNA concentration in laboratory experimental systems. Alonso,M.C., Rodriguez,V., Rodriguez,J., Borrego,J.J. (2000). Journal of Experimental Marine Biology and Ecology 244:239-252. Several marine bacteriophages, a ciliate (Uronema sp.), and a flagellate (Pseudobodo sp.) were used to study comparatively the grazing and clearance rates of four marine bacteria. Bacteria were fluorescently labelled using rhodamine isothiocyanate. The results obtained indicate that bacteriophages and flagellates caused a significantly higher (P < 0.025) decrease in the number of marine bacteria compared to the ciliate Uronema sp. The role of bacteriophages, ciliates and flagellates in the production of dissolved-DNA (D-DNA) was also studied. The interaction between both bacteriophages and protists with marine bacteria are responsible for an increase of the D-DNA concentration, although a direct relationship between D-DNA concentration and predator number was only obtained from experiments performed with Uronema sp. [TOP OF PAGE]

  76. Microbiological quality of the Catania coastal sea water. Aulicino,F.A., Mauro,L., Marranzano,M., Biondi,M., Ursino,A., Carere,M. (2000). Annali di Igiene 12:533-541. This study was carried out from 1997 to 1998 along a selected coastal area near Catania to ascertain bacteriological and virological quality of marine waters. 44 seawater samples, collected from 4 stations, were assayed for the presence of total and fecal coliforms, fecal streptococci, coliphages, Salmonellae and enteric viruses. Two stations localized at canal outfalls showed high levels of fecal pollution. The other stations were of good microbiological quality and showed a limited number of samples exceeding the standards laid down as guide values for bathing waters by Italian normative during the bathing period. Salmonellae were isolated in 8 out of 44 sea water samples (18%). Their presence was ascertained mainly in samples of the two polluted stations. Enteroviruses were not isolated. Enteric viruses such as Reoviruses were isolated from all stations, in 12 out of 44 samples (27%). The presence of these viruses was ascertained only during autumnal and winter seasons. The results of this study showed that, notwithstanding some stations showed high levels of bacteriological indicators of fecal pollution and presence of Salmonellae, enteroviruses growing on cell cultures were not isolated. Reoviruses confirmed their high diffusion in marine waters. [TOP OF PAGE]

  77. The presence of viruses and bacteria along the Adriatic Coast. Aulicino,F.A., Ammazzalorso,P., Ercolessi,M., Banini,L., Silverii,G., Orsini,P., Mastrantonio,A., Bellucci,C., Carere,M. (2000). Ig. Mod. 113:99-116. A study was carried out on seawater samples, collected from the Adriatic sea near the coast of Pesaro, to determine the presence of enteric viruses and Escherichia coli bacteriophages besides the common indicators of fecal pollution and of trophic conditions of the marine environment (Pseudomonas, Vibrio, algae). During 1994-95, seawater samples were tested in 8 stations located in seaside resorts; in 1994 samples of sediment were also analyzed. Generally the results showed a good situation from the microbiological and eutrophic point of view. Only 2 stations showed fecal pollution. Enteroviruses were not detected while Reovirus was isolated from samples of the two most contaminated stations and from a not polluted area. [TOP OF PAGE]

  78. Light scattering by viral suspensions. Balch,W.M., Vaughn,J., Novotny,J., Drapeau,D.T., Vaillancourt,R., Lapierre,J., Ashe,A. (2000). Limnol. Oceanogr. 45:492-498. Viruses represent one of the most abundant, ocean-borne particle types and have significant potential for affecting optical backscattering. Experiments addressing the light-scattering properties of viruses have heretofore not been conducted. Here we report the results of laboratory experiments in which the volume-scattering functions of several bacterial viruses (bacteriophages) were measured at varying concentrations with a laser light-scattering photometer using a He-Ne and/or Argon ion laser (632.8 and 514.0 nm, respectively). Four bacterial viruses of varying size were examined, including the coliphages MS-2 (capsid size 25-30 nm) and T-4 (capsid size apprx100 nm), and marine phages isolated from Saco Bay, Maine (designation Y-1, capsid size 50-80 nm) and Boothbay Harbor, Maine (designation C-2, capsid size apprx110 nm). Volume-scattering functions (VSFs) were fitted with the Beardsley-Zaneveld function and then integrated in the backward direction to calculate backscattering cross section. This was compared to the virus geometric cross section as determined by transmission electron microscopy and flow-field fractionation. Typical backscattering efficiencies varied from 20 X 10-6 to 1,000 X 10-6. Data on particle size and backscattering efficiencies were incorporated into Mie scattering calculations to estimate refractive index of viruses. The median relative refractive index of the four viruses was apprx1.06. Results presented here suggest that viruses, while highly abundant in the sea, are not a major source of backscattering. [TOP OF PAGE]

  79. Evolution of life's fringes. Balter,M. (2000). Science 289:1866-1867. Fresh evidence that viruses have existed for billions of years has scientists wondering what role these stripped-down microbes played in evolution. [TOP OF PAGE]

  80. Viral density and virus-to-bacterium ratio in deep-sea sediments of the Eastern Mediterranean. Danovaro,R., Serresi,M. (2000). Appl. Environ. Microbiol. 66:1857-1861. Viruses are now recognized as a key component in pelagic systems, but their role in marine sediment has yet to be assessed. In this study bacterial and viral densities were determined at nine deep-sea stations selected from three main sites (i.e., the Sporades Basin, the Cretan Sea, and the Ierapetra Trench at depths of 1,232, 1,840, and 4,235 m, respectively) of the Eastern Mediterranean. The three areas were characterized by different phytopigment and biopolymeric carbon concentrations and by changes in the protein and carbohydrate pools. A gradient of increasing trophic conditions was observed from the Sporades Basin (North Aegean) to the Ierapetra Trench (South Aegean). Viral densities (ranging from 1 x 109 to 2 x 109 viruses ml of sediment(-1)) were significantly correlated to bacterial densities (n = 9, r2 = 0.647) and reached values up to 3 orders of magnitude higher than those generally reported for the water column. However, the virus-to-bacterium density ratio in deep-sea sediments was about 1 order of magnitude lower (range of 2 to 5, with a modal value of 2.6) than in pelagic environments. Virus density decreased vertically with depth in sediment cores at all stations and was below detection limits at the 10-cm depth of the abyssal sediments of the Ierapetra Trench. Virus density in the sediment apparently reflected a gradient of particle fluxes and trophic conditions, displaying the highest values in the Sporades Basin. The low virus-to-bacterium ratios and their inverse relationship with station depth suggest that the role played by viruses in controlling deep-sea benthic bacterial assemblages and biogeochemical cycles is less relevant than in pelagic systems. [TOP OF PAGE]

  81. Pulsed-field gel electrophoresis analysis of virus assemblages present in a hypersaline environment. Diez,B., Anton,J., Guixa-Boixereu,N., Pedros-Alio,C., Rodriguez-Valera,F. (2000). International Microbiology 3:159-164. A method for analyzing virus assemblages in aquatic environments was developed and used for studying the highest-salinity ponds (from 13.4 to 35% salinity) from a multi-pond solar saltern in Alicante, Spain. The protocol consisted of a series of concentration and purification steps including tangential flow filtration and ultracentrifugation, followed by the preparation of total viral nucleic acids that were subsequently separated by pulsed-field gel electrophoresis. For every sample analyzed, a characteristic DNA pattern was obtained, whose complexity was related to viral diversity. The comparison of our results with a similar analysis carried out with marine virus assemblages shows that, as expected, the viral diversity corresponding to the analyzed hypersaline environment is considerably lower than that of a marine environment. [TOP OF PAGE]

  82. Causative agents of bacterial mortality and the consequences to marine food webs. Fuhrman,J.A., Noble,R.T. (2000). p. ??? In Bell,C.R., Brylinsky,M., and Johnson-Green,P. (eds.), Microbial Biosystems: New Frontiers. Atlantic Canada Society for Microbial Ecology, Halifax, Canada. [TOP OF PAGE]

  83. Ultraviolet radiation effects on bacterioplankton and viruses in marine ecosystems. Jeffrey,W.H., Kase,J.P., Wilhelm,S.W. (2000). pp. 206-236. In In De Mora,S.J. and et al. (eds.), Effects Of UV Radiation On Marine Ecosystems. Cambridge University Press, Cambridge. [TOP OF PAGE]

  84. Genomic sequence of a lytic cyanophage of Synechococcus spp. Lu,J.R., Chen,F., Hodson,R.E. (2000). Abstracts of the General Meeting of the American Society for Microbiology 100, 465. [TOP OF PAGE]

  85. Bacterial growth rate and marine virus–host dynamics. Middelboe,M. (2000). Microb. Ecol. 40:114-124. The dynamics of a marine virus–host system were investigated at different steady state growth rates in chemostat cultures and the data were analyzed using a simple model. The virus–host interactions showed strong dependence on host cell growth rate. The duration of the infection cycle and the virus burst size were found to depend on bacterial growth rate, and the rate of cell lysis and virus production were positively correlated with steady state growth rate in the cultures (r 2 > 0.96, p < 0.05). At bacterial growth rates of 0.02 to 0.10 h-1 in the chemostats the virus burst size increased from 12 ± 4 to 56 ± 4, and the latent period decreased from 2.0 to 1.7 h. Resistant clones of the host strain were present in the cultures from the beginning of the experiment and replaced the sensitive host cells following viral lysis in the cultures. Regrowth of resistant cells correlated significantly (r 2 = 1.000, p < 0.02) with the lysis rate of sensitive cells, indicating that release of viral lysates stimulated growth of the non-infected, resistant cells. The constructed model was suitable for simulating the observed dynamics of the sensitive host cells, viruses and resistant clones in the cultures. The model was therefore used in an attempt to predict the dynamics of this virus–host interaction in a natural marine environment during a certain set of growth conditions. The simulation indicated that a steady state relationship between the specific viruses and sensitive and resistant bacterial clones may occur at densities that are reasonable to assume for natural environments. The study demonstrates that basic characterization and modeling of specific virus–host interactions may improve our understanding of the behavior of bacteria and viruses in natural systems. [TOP OF PAGE]

  86. Rapid movement of wastewater from on-site disposal systems into surface waters in the Lower Florida Keys. Paul,J.H., McLaughlin,M.R., Griffin,D.W., Lipp,E.K., Stokes,R., Rose,J.B. (2000). Estuaries 23:662-668. Viral tracer studies have been used previously to study the potential for wastewater contamination of surface marine waters in the Upper and Middle Florida Keys. Two bacteriophages, the marine bacteriophage phiHSIC and the Salmonella phage PRD1, were used as tracers in injection well and septic tank studies in Saddlebunch Keys of the Lower Florida Keys and in septic tank studies in Boot Key Harbor, Marathon, of the Middle Keys. In Boot Key Harbor, both phages were detected in a canal adjacent to the seeded septic tank within 3 h 15 min of the end of the seed period. The tracer was then detected at all sampling sites in Boot Key Harbor, including one on the opposite side of U.S. Highway 1 in Florida Bay, and at an Atlantic Ocean beach outside Boot Key Harbor. Rates of migration based on first appearance of the phage ranged from 1.7 to 57.5 m h-1. In Saddlebunch Keys, phiHSIC and PRD1 were used to seed a residential septic tank and a commercial injection well. The septic tank tracer was not found in any surface water samples. The injection well tracer was first detected at a site most distant from the seed site, a channel that connected Sugarloaf Sound with the Atlantic Ocean. The rate of tracer migration from the injection well to this channel ranged from 66.8 to 141 m h-1. Both tracer studies showed a rapid movement of wastewater from on-site sewage treatment and disposal systems in a southeasterly direction toward the reef tract and Atlantic Ocean, with preferential movement through tidal channels. These studies indicate that wastewater disposal systems currently in widespread use in the Florida Keys can rapidly contaminate the marine environment. [TOP OF PAGE]

  87. Evaluation of marine bacterial lysogens for use in a mutagen detection (Prophage Induction) assay. Paul,J.H., Griffin,D.W., Crespo-Gomez,J., McDaniel,L., McLaughlin,M.R. (2000). Abstracts of the General Meeting of the American Society for Microbiology 100, 464. [TOP OF PAGE]

  88. Ecology of bacteriophages in nature. Paul,J.H., Kellogg,C.A. (2000). pp. 211-246. In In Hurst,C.J. (ed.), Viral Ecology. Academic Press, San Diego. [first paragraph] The role of bacteriophages (viruses that infect bacteria) in the environment has been the subject of intense investigation over the past several years. The development of techniques to study natural viral populations in situ has progressed tremendously. Various aspects of bacteriophage ecology in nature - including abundance, role in microbial mortality and water column trophodynamics, viral decay rates, repair mechanisms, and lysogeny - are now becoming or are nearly understood. However, most of these studies have been performed in aquatic environments. Thus, this review will mainly be limited to a discussion of aquatic environments. For reviews of the earlier literature, the reader is referred to Moebus (1987), Goyal et a2. (1987), Fuhrman and Suttle (1993), Ackermann and DuBow (1987), and Proctor (1997). [TOP OF PAGE]

  89. Occurrence of coliphages in fish and aquaculture farms. Rao,B.M., Surendran,P.K. (2000). Fishery Technology 37:146-149. Coliphages were detected in water samples collected from brackish water and fresh water fish farms. Coliphages were also detected in the farmed fresh water fish, common carp and marine fish, oil sardine, from local market. Coliphage levels obtained were as follows:- water from brackish water fish farm 3, water from fresh water fish farm 23, fresh water fish 240 pfu.g-1 and marine fish 3500 pfu.g-1. [TOP OF PAGE]

  90. The complete genomic sequence of the marine phage Roseophage SIO1 shares homology with nonmarine phages. Rohwer,F., Segall,A., Steward,G., Seguritan,V., Breitbart,M., Wolven,F., Azam,F. (2000). Limnol. Oceanogr. 45:408-418. Viruses are ubiquitous components of the marine environment, frequently reaching concentrations of 107-108 viruses per milliliter of surface seawater The majority of these viral particles are bacteriophages (phages). Although the oceans are probably the largest pool of bacteriophages on the planet, the evolutionary relationships of marine phages to phages from other environments are unknown. To address this issue, we have completely sequenced the genome of the lytic marine phage, Roseophage SIO1, that infects the heterotrophic marine bacterium Roseobacter SIO67. This phage has an isometric capsid with a diameter of approximately 43 nm, a short tail, a buoyant density of 1.49 g cm-3 in CsCl, and a 39,906-bp dsDNA genome. Sequence similarities and relative positions within the genome suggest that three of the open reading frames (ORFs) are homologous to the primase, DNA polymerase, and endodeoxyribonuclease I proteins of coliphages T3 and T7. The results are consistent with the mosaic theory of phage evolution and indicate a genetic link between marine and nonmarine phages. Additionally, basic life histories of marine phages can be elucidated by comparison of complete genomes to those of other extensively studied phages (e.g., lambda, T4, T7). The DNA replication machinery of Roseophage SIO1 shows a clear homology with that of coliphages T3 and T7, suggesting that the process of DNA replication may be similar among these phages. The Roseophage SIO1 genome also encodes four predicted proteins involved in phosphate metabolism (RP PhoH, RP ribonucleotide reductase, RP Thy1, and RP endodeoxyribonuclease I) suggesting that phosphate recycling is important to Roseophage SIO1's life cycle. Other interesting clues about Roseophage SIO1's life history come from the absence of certain expected protein regions. For example, we have not been able to identify the Roseophage SIO1 structural proteins (e.g., capsid proteins) by homology to other phages. It is also conspicuous that the Roseophage SIO1 genome lacks a recognizable RNA polymerase, an essential component of T3 and T7 life cycles. Analysis of the Roseophage SIO1 genome shows that marine and nonmarine phages are genetically related but basic life histories may be significantly different. [TOP OF PAGE]

  91. Genome size distributions indicate variability and similarities among marine viral assemblages from diverse environments. Steward,G., Montiel,J., Azam,F. (2000). Limnol. Oceanogr. 45:1697-1706. [TOP OF PAGE]

  92. Analysis of marine viral assemblages. Steward,G.F., Azam,F. (2000). pp. 159-165. In In Bell,C.R., Brylinski,M., and Johnson-Green,P. (eds.), Microbial Biosystems: New Frontiers. Atlantic Canada Society for Microbial Ecology, Halifax, Canada. Viruses are the numerically dominant microbes in every oceanic environment from the surface into the sediments. A liter of surface seawater from a typical mesotrophic area contains 1010 of them, about ten times more than bacteria. While total counts of viruses are becoming easier to make, we still know very little about the viruses that comprise a given assemblage. Infectivity assays are extremely useful and still the best way to assay for infectious viruses for any particular host. However, this approach requires that each potential host organism be cultured, making it impractical if not impossible to completely characterize natural assemblages. Morphological studies have been enlightening, but are time consuming and difficult to do quantitatively. Here we report a fingerprinting approach to characterize natural viral assemblages. In this approach, viruses are concentrated and intact viral genomes are separated based on their size via pulsed-field gel electrophoresis. The number of distinguishable bands provides a minimum estimate of the number of different viruses, while band position and staining intensity reveal the genome size distribution within the assemblage. With this technique we have detected spatial and temporal differences, as well as many similarities, in viral assemblages among a variety of marine habitats. Current efforts are directed toward combining this technique with other methods of fractionation and sequence analysis to allow both morphological and genetic description of uncultivated marine viruses. Direct investigation of dominant or particularly widespread viruses may ultimately provide clues as to which marine organisms contribute most to the viral pool, and which organisms are likely to be significantly influenced by viral mortality. [TOP OF PAGE]

  93. Genome size distributions indicate variability and similarities among marine viral assemblages from diverse environments. Steward,G.F., Montiel,J.L., Azam,F. (2000). Limnol. Oceanogr. 45:1697-1706. Pulsed field gel electrophoresis (PFGE) was used to determine the size distributions of virus-like DNA in seawater from diverse environments (Arctic Ocean, Ross Sea, Coastal Pacific Ocean, and Northern Adriatic Sea). Changes in DNA banding patterns indicated that shifts in the viral assemblage composition occurred on the order of = 2 d during an intense dinoflagellate bloom in coastal Pacific waters. Different DNA banding patterns from diverse locations also indicated spatial variability in composition, but all of the samples analyzed had similar features. Size frequency distributions for virus-like genomes (VLGs) were multi-modal with major peaks occurring around 31-36 kilobases (kb) and 58-63 kb. The smallest discrete band resolved was 26 kb and the largest was >200 kb and the overall mean virus-like genome size was 50 ± 4 kb (mean ± sd, n = 30). On average, in surface seawater, > 90% of the VLGs occurred in the 26-69 kb size range and at least half were between 28 to 45 kb. This first extensive survey of viral genome sizes in seawater indicates that most marine viruses have physical properties similar to other known viruses. The distributions revealed that the vast majority of the detected VLGs have sizes typical of bacteriophages while only a few percent were in the size range of known algal viruses. [TOP OF PAGE]

  94. Cyanophages and their role in the ecology of cyanobacteria. Suttle,C.A. (2000). pp. 563-589. In In Whitton,B.A. and Potts,M. (eds.), The Ecology of Cyanobacteria: Their Diversity in Time and Space. Kluwer Academic Publishers, Boston. Cyanophages belong to three recognized families of double-stranded DNA viruses; Myovirida (contractile tails); Styloviridae (long non-contractile tails); and Podoviridae (short tails). They have a complex pattern of host ranges, are widely distributed, and can be readily isolated from marine and fresh waters. Although cyanophages are related to other bacteriophages, it is likely that they evolved more than 3 billion years ago when cyanobacteria diverged from other prokaryotes. In marine waters, genetically-diverse Myoviridae which infected Synechococcus spp. are the most abundant cyanophages; Styloviridae and Podoviridae are most commonly isolated from fresh waters. Morphological evidence also suggests that freshwater and marine myoviruses are more closely related to each other than they are to other bacteriophages. Cyanophages that infect phycoerythrin-rich Synechococcus spp. can be extremely abundant in coastal marine environments where they can occur at titers in excess of 10[6] mL[-1] and 10[5] g[-1] of sediment. In surface waters abundance varies over orders of magnitude on a seasonal basis. Abundance follows that of Synechococcus, with evidence for a threshold in Synechococcus of ca. 10[3] to 10[4] mL[-1] beyond which cyanophage abundance increases greatly. In nearshore waters the high concentrations of cyanophages and Synecoccus result in high encounter frequencies and selection for Synecoccus communities that are largely resistant to infection. Encounters are much less frequent offshore and this leads to the appearance of a community that appears to have low resistance to infection. In freshwaters, viruses which infect filamentous cyanobacteria appear to be most abundant and also show strong seasonal dynamics however; even in the most eutrophic environments titers are orders of magnitude less than in productive coastal waters. Little effort was made to screen freshwaters for cyanophages that infect phycoerythrin-rich Synechococcus. In marine surface waters turnover times for cyanophage populations range from hours to days. Solar radiation has a major effect on cyanophage infectivity and results in the selection of cyanophage communities that are more resistant to destruction by sunlight during summer. In constrast to surface waters, infectious cyanophages can persist in sediments for at least 100 years. Although the effect of cyanophages on the mortality of cyanobacterial communities is likely to be variable, current estimates suggest that cyanophages are responsible for the removal of approximately 3% of marine Synechococcus on a daily basis. In addition to the lytic infection, lysogenic associations were clearly demonstrated in filamentous and unicellular cyanobacteria, but the ecological implications of lysogeny remain unexplored. Environmental factors and the physiological state of cyanobacteria clearly affect cyanophage-cyanobacterial interactions but remain poorly understood. [TOP OF PAGE]

  95. The ecology, evolutionary and geochemical consequences of viral infection of cyanobacteria and eukaryotic algae. Suttle,C.A. (2000). pp. 248-286. In In Hurst,C.J. (ed.), Viral Ecology. Academic Press, New York. [first paragraph] More than 35 years ago, Safferman and Morris (1963) reported the isolation of a virus (cyanophage) that infected a freshwater filamentous “blue-green alga.” This discovery stimulated research that led to isolation of many viruses that infect freshwater cyanobacteria. Although the potential for viruses to control cyanobacterial blooms was recognized (Safferman and Morris, 1964; Shilo, 1971), much of this work focused on the biology rather than the ecology of cyanophages (reviewed in Brown, 1972; Padan and Shilo, 1973; Safferman, 1973; Stewart and Daft, 1977; Sherman and Brown, 1978; Martin and Benson, 1988). At about the same time, evidence for viral infection of eukaryotic algae was beginning to emerge with reports by Zavarzina (1961, 1964) of lysis of Chlorella pyrenoidosa cultures. However, it was not until a decade later that observations of viruslike particles (VLPs) in eukaryotic algae began to appear in the literature (e.g., Lee, 1971; Chapman and Lang, 1973; Lemke, 1976; Dodds, 1979, 1983), and shortly thereafter a virus (CCV) was isolated that infected the macroalga Cham corullina (Gibbs et al., 1975; Skotnicki et al., 1976). This was followed a few years later by isolation of a virus (MPV) that infected the marine photosynthetic flagellate Micromonas pusilla (Mayer, 1978; Mayer and Taylor, 1979). Despite the ecological implications of viruses infecting major primary producers in aquatic environments, interest in viruses that infect eukaryotic algae was slow to gather. In fact, after the work by Waters and Chan (1982), there was little further interest in MPV, and the virus was lost from culture (F. J. R. Taylor, personal communication). Furthermore, by the 1980s ecological interest in cyanophages also began to wane as cyanobacterial blooms were brought under control by regulations reducing nutrient inputs to lakes. The decline in interest was exacerbated by the lack of appreciation by many algal and aquatic ecologists of the ecological importance of microbes in general and of viruses in particular. Although there was little interest in the ecological aspects, there were major advances in our understanding of the biology of a group of viruses that infect Chlorella-like algae that are symbionts of Hydra viridis and Paramecium bursaria. These viruses were isolated in the early 1980s and possess a number of unusual features (reviewed in Van Etten et al., 1991; Reisser, 1993; Van Etten, 1995; Van Etten and Meints, 1999) that led to the creation of a new family of viruses, Phycodnaviridae (Van Etten and Ghabrial, 1991). As well, work has progressed on a group of widely distributed viruses that infect filamentous brown algae belonging to order Ectocarpales (Oliveira and Bisalputra, 1978; Muller, 1991; Henry and Meints, 1992; Muller and Frenzer, 1993; Muller, 1996; Van Etten and Meints, 1999). [TOP OF PAGE]

  96. Elements of a theory for the mechanisms controlling abundance, diversity, and biogeochemical role of lytic bacterial viruses in aquatic systems. Thingstad,T.F. (2000). Limnol. Oceanogr. 45:1320-1328. Mechanisms controlling virus abundance and partitioning of loss of bacterial production between viral lysis and protozoan predation are discussed within the framework of an idealized Lotka-Volterra-type model. This combines nonselective protozoan predation with host-selective viral lysis of bacteria. The analysis leads to a reciprocal relationship between bacterial diversity and viruses, in which coexistence of competing bacterial species is ensured by the presence of viruses that “kill the winner,” whereas the differences in substrate affinity between the coexisting bacterial species determine viral abundance. The ability of the model to reproduce published observations, such as an approximate 1:10 ratio between bacterial and viral abundance, and the ability of viral lysis to account for 10-50% of bacterial loss are discussed. [TOP OF PAGE]

  97. Quantification of algal viruses in marine samples. Wilhelm,S.W., Poorvin,L. (2000). Methods in Microbiology 30:??? [TOP OF PAGE]

  98. Bacterial carbon production in Lake Erie is influenced by viruses and solar radiation. Wilhelm,S.W., Smith,R.E.H. (2000). Canadian Journal of Fisheries and Aquatic Sciences 57:317-326. Bacterial production is an integral recycling mechanism that facilitates carbon flow through aquatic food webs. Factors influencing bacterial activity therefore impact carbon flow. Although ecologists consider grazing and dissolved organic carbon flux to be the major regulators of bacterial activity, we explored two other important pressures. Virus-like particle abundance ranged from 3.7 to 37.9 x 1010 L-1 in samples collected during August 1997 and July 1998. Bacterial abundance during these periods ranged from 1.8 to 4.6 x 109 L-1. Based on electron microscopic analysis, viruses in Lake Erie would have been responsible for 12.1 to 23.4 % of bacterial mortality and, in quasi-steady state conditions, a comparable loss of bacterial productivity. In the central basin, solar radiation was also demonstrated to regulate bacterial productivity. Ultraviolet radiation (UVR, 295-400 nm) was shown to inhibit bacterial productivity according to a cumulative exposure kinetic model, and biological weighting functions were derived to enable calculation of time- and depth-integrated photoinhibition. The daytime photoinhibitory loss of bacterial carbon production was estimated to be 14 to 30% over the upper 5 m, primarily due to UVR > 320 nm. Viruses and sunlight are therefore of comparable importance as regulators of bacterial activity in this system. [TOP OF PAGE]

  99. Interaction of a marine virus with its host: Lysogeny or Pseudolysogeny? Williamson-Smith,S.J., McLaughlin,M.R., Paul,J.H. (2000). Abstracts of the General Meeting of the American Society for Microbiology 100, 464-465. [TOP OF PAGE]

  100. Transmission electron microscope analysis of viruses in the freshwater lakes of Signy Island, Antarctica. Wilson,W.H., Lane,D., Pearce,D., Ellis-Evans,J.C. (2000). Polar Biology 23:657-660. [TOP OF PAGE]

  101. Virioplankton: viruses in aquatic ecosystems. Wommack,K.E., Colwell,R.R. (2000). Microbiol. Mol. Biol. Rev. 64:69-114. [FIRST TWO PARAGRAPHS] From studies of the genetics and biology of viruses has come a more profound understanding of the basic biological processes of life, not the least of which has been the discovery of DNA as the carrier molecule of genetic information (125) and mRNA as an intermediate molecule in the transfer of genetic information to the ribosomes (43). Other breakthroughs in molecular biology attributable to bacteriophage models are the definition and mapping of the first gene (18); discovery of the discontinuous nature of DNA replication (222); discovery of restriction endonucleases (212); and the mechanics of gene regulation (261). Indeed, basic research on the biology of the bacteriophage has been fundamental to the establishment of the field of molecular biology (73). The value of basic research to technological and economic advancement is perhaps best illustrated by the historical link between basic bacteriophage biology and the present-day, multibillion dollar biotechnology industry. ¶ In contrast to extensive information on the biology and genetics of viruses, there is only a limited understanding of the diversity of host populations. In general, the discussion is focused on in situ measurement of virioplankton populations. Model phage-host systems are included, as appropriate, for background information. Readers interested in aquatic phagehost relationships will find relevant information in reviews by Børsheim (29) and Proctor (253) and an earlier review by Moebus (193). A brief synopsis of current views on marine virus ecology was recently provided by Furhman (91). The distribution and survival of human and animal pathogenic enteroviruses in aquatic environments are not covered herein, since detection and distribution of human disease-causing viruses in natural waters have been extensively reviewed elsewhere (99, 103, 104, 112, 182). [TOP OF PAGE]

  102. Reconsidering the relationship between virally induced bacterial mortality and frequency of infected cells. Binder,B. (1999). Aquat. Microb. Ecol. 18:207-215. The relative contribution of viral lysis to overall mortality in aquatic bacterial populations is often estimated as twice the frequency of infected cells (FIC). The `factor-of-two rule' upon which this estimate is based assumes (1) steady-state conditions, (2) that latent period is equivalent to generation time, and (3) that infected cells are not grazed. FIC values for this calculation are themselves derived from measurements of the frequency of visibly infected cells (FVIC) by the use of a simple conversion factor. A steady-state model was developed to more rigorously define the relationships between FIC, FVIC, and the fraction of mortality from viral lysis (FMVL). This model shows that even under the restrictive assumptions listed above, the factor-of-two rule systematically overestimates FMVL for typically reported values of FVIC. The model also shows that although grazing on infected cells further reduces FMVL for a given estimate of FIC, at the same time such grazing increases FIC for a given measurement of FVIC. In combination, these 2 effects minimize the influence of grazing on the calculation of FMVL from FVIC. Overall, the relationship between FMVL and FVIC is well approximated as follows: FMVL epsilon FVIC/[ gamma ln(2) (1 - epsilon - FVIC)], where gamma = the ratio between the latent period and generation time, and \g?\ = the fraction of the latent period during which viral particles are not yet visible. Using typically observed values of FVIC, and assuming that gamma = 1 (per assumption 2, above) and \g?\ = 0.186 (per literature estimates), the model suggests that, on average, viral lysis accounts for approximately 22% (range: 4.5 to 45%) of total bacterial mortality in a range of aquatic environments, corresponding to a mean overestimate of 24% (range: 4 to 44%) by the factor-of-two rule. Perhaps most importantly, the model shows that calculations of FMVL from FIC or FVIC are very sensitive to changes in the relative length of the latent period ( gamma ) and in the assumed proportion of the latent period during which viral particles are not recognizable ( epsilon ). Constraining these 2 factors would greatly improve the reliability of FMVL calculations. [TOP OF PAGE]

  103. Flow cytometric analyses of virus infection in two marine phytoplankton species, Micromonas pusilla (Prasinophyceae) and Phaeocystis pouchetii (Prymnesiophyceae). Brussaard,C.P.D., Thyrhaug,R., Marie,D., Bratbak,G. (1999). J. Phycol. 35:941-948. Cell characteristics of two axenic marine phytoplankton species, Micromonas pusilla (Butscher) Manton et Parke and Phaeocystis pouchetii (Hariot) Lagerheim, were followed during viral infection using flow cytometry, Distinct differences between noninfected and infected cultures were detected in the forward scatter intensities for both algal species. Changes in side scatter signals on viral infection were found only for P, pouchetii. Chlorophyll red fluorescence intensity per cell decreased gradually over time in the infected cultures, DNA analyses were performed using the nucleic acid-specific fluorescent dye SYBR Green I. Shortly after infection the fraction of algal cells with more than one genome equivalent increased for both species because of the replication of viral DNA in the infected cells. Over time, a population of algal cells with low red autofluorescence and low DNA fluorescence developed, likely representing algal cells just prior to viral lysis, The present study provides insight into basic virus-algal host cell interactions. It shows that flow cytometry can be a useful tool to discriminate between virus infected and noninfected phytoplankton cells. [TOP OF PAGE]

  104. Device and method for phage-based antibiotic susceptibility testing. Cottingham,H.V. (1999). Becton Dickinson and Company. 883722(5,858,693). Franklin Lakes, NJ. A phage-based antibiotic susceptibility test is carried out by maintaining a patient sample in a sealed sample well during addition of the phage and Luciferin substrate used in the test, in order to prevent contamination of the laboratory environment. The phage is adhered in dried form to a metal carrier disk which is retained beneath the cap of the sealed sample well by means of an external magnet, and is mixed with the patient sample by removing the external magnet and allowing the carrier disk to fall to the bottom of the sample well. The Luciferin substrate is adhered to the underside of the cap and is mixed with the patient sample by shaking or inverting the sealed sample well after the metal carrier disk has separated from the underside of the cap. A row of connected sample wells and caps may be employed to allow the same patient sample to be tested with multiple antibiotics. [TOP OF PAGE]

  105. Marine viruses and their biogeochemical and ecological effects. Fuhrman,J.A. (1999). Nature 399:541-548. Viruses are the most common biological agents in the sea, typically numbering ten billion per litre. They probably infect all organisms, can undergo rapid decay and replenishment, and influence many biogeochemical and ecological processes, including nutrient cycling, system respiration, particle size-distributions and sinking rates, bacterial and algal biodiversity and species distributions, algal bloom control, dimethyl sulphide formation and genetic transfer. Newly developed fluorescence and molecular techniques leave the field poised to make significant advances towards evaluating and quantifying such efforts. [TOP OF PAGE]

  106. Impact of viruses on planktonic bacteria. Fuhrman,J.A. (1999). p. ??? In Kirchman,D.L. (ed.), Microbial Ecology of the Oceans. Wiley & Sons, ??? [TOP OF PAGE]

  107. Enteroviruses in the recreational waters of Lake Orta. Maiello,A., Guidetti,A., Poncetta,D., Ossola,O., Guidetti,L., Buttinelli,G., Fiore,L., Ruggenini,A.M. (1999). Lakes Reservoirs Research and Management 4:93-99. The water quality of Lake Orta was evaluated for recreational use. This lake was the only Italian lake to undergo a 'liming treatment' which neutralizes water acidity by adding carbonates. Chemical, bacteriological and virological parameters were monitored for 3 years after the treatment ended. Chemical and bacteriological studies were performed according to national standard methods (DPR 470/82) whereas F' specific bacteriophage were enumerated according to an international standard (ISO 10705-1). Enteroviruses were detected by the observation of a cytophatic effect on buffalo green monkey cultures. Also, the possibility of applying molecular biological techniques for enterovirus detection directly to waters concentrated without previous isolation of viruses in cell culture was verified. The sensitivity, specificity and feasibility of both methods were evaluated. The association between the direct detection of enteroviruses and the indirect indication of their presence by the presenceof bacteriophages, and the relationship between bacteriophage presence and bacteriological contamination were also evaluated. In the course of surveillance, none of the samples infringed the law with respect to the physical-chemical parameter (pH < 6). As far as bacteriological characteristics were concerned, 16.6% of the samples taken in 1993 infringed the law, as well as 19.4% of samples in 1994 and 19.4% in 1995. The level of faecal coliforms most frequently exceeded the given limits. The detection test for enteroviruses was positive in 5.1% of the samples using the traditional method with cell culture, and it was positive in 7.6% using the antigen capture polymerase chain reaction (AC-PCR) method directly applied to concentrated waters, indicating the feasibility and a higher sensitivity of the AC-PCR method compared to cell culture. Bacteriophages were present in all the samples that were positive in the virological analysis, as well as in 46.7% of negative samples. [TOP OF PAGE]

  108. Seasonal changes in densities of cyanophage infectious to Microcystis aeruginosa in a hypereutrophic pond. Manage,P., Kawabata,Z., Nakano,S. (1999). Hydrobiologia. 411:211-216. Seasonal changes in densities of cyanophages infectious to Microcystis aeruginosa were studied in a hypereutrophic pond from March 1997 to January 1998 to elucidate the potential impact of the cyanophage on M. aeruginosa mortality. Densities of M. aeruginosa ranged between 1.8 X 104 and 9.4 X 105 cells ml-1, while those of the cyanophages were between 2.0 X 102 and 4.2 X 104 PFU ml-1. Sharp decreases in densities of M. aeruginosa were detected on 10 June and 24 September, as densities of the cyanophages increased, suggesting release of the cyanophages due to the lysis of infected M. aeruginosa. Thus, infection by cyanophages may have a substantial effect on cyanobacterial succession in the pond. Densities of cyanophages became undetectable when those of M. aeruginosa were at low levels during winter. We suggest that there is a tight host-pathogen relationship between M. aeruginosa and the cyanophage in the pond. [TOP OF PAGE]

  109. Enumeration of marine viruses in culture and natural samples by flow cytometry. Marie,D., Brussaard,C.P.D., Thyrhaug,G., Bratbak,G., Vaulot,D. (1999). Appl. Environ. Microbiol. 65:45-52. Flow cytometry (FCM) was successfully used to enumerate viruses in seawater after staining with the nucleic acid-specific dye SYBR Green-I. The technique was first optimized by using the Phaeocystis lytic virus PpV-01. Then it was used to analyze natural samples from different oceanic locations. Virus samples were fixed with 0.5% glutaraldehyde and deep frozen for delayed analysis. The samples were then diluted in Tris-EDTA buffer and analyzed in the presence of SYBR Green-I. A duplicate sample was heated at 80 degree C in the presence of detergent before analysis. Virus counts obtained by FCM were highly correlated to, although slightly higher than, those obtained by epifluorescence microscopy or by transmission electron microscopy (r = 0.937, n = 14, and r = 0.96, n = 8, respectively). Analysis of a depth profile from the Mediterranean Sea revealed that the abundance of viruses displayed the same vertical trend as that of planktonic cells. FCM permits us to distinguish between at least two and sometimes three virus populations in natural samples. Because of its speed and accuracy, FCM should prove very useful for studies of virus infection in cultures and should allow us to better understand the structure and dynamics of virus populations in natural waters. [TOP OF PAGE]

  110. Cyanophages. Martin,E.L., Kokjohn,T.A. (1999). pp. 324-332. In In Granoff,A. and Webster,R.G. (eds.), Encyclopedia of Virology second edition. Academic Press, San Diego. The cyanobacteria with their prokaryotic structure and oxygenic photosynthesis occupy a unique position among living organisms. These characteristics closely relate them not only to the eubacteria, but also to eucaryotic algae and plants. Over the last 5 or 6 years research has continued to investigate the genetics, physiology, and metabolism, primarily for cyanophages which replicate in both unicellular and filamentous freshwater cyanobacteria; however, the major impetus of the latest research has shifted to the role cyanophages occupy in marine ecosystems. Cyanophages are of critical importance in that they can cause substantial lysis of primary producer organisms. This in turn can exert an extensive effect on the dynamics of carbon flow in many of the marine environments studied. It is hoped that many of the aspects of the research described here can continue to come together to give a more interconnected and complete understanding of the interactions between cyanophages and cyanobacteria. [TOP OF PAGE]

  111. Breakdown and microbial uptake of marine viruses and other lysis products. Noble,R.T., Fuhrman,J.A. (1999). Aquat. Microb. Ecol. 20:1-11. To understand the roles of marine viruses in marine microbial food webs, it is important to determine rates and mechanisms of virus degradation and subsequent uptake of degraded virus material and other cell lysis products by heterotrophic marine bacteria. We radiolabeled and concentrated viruses and viral lysis products from either pure cultures (3H) or natural communities (3H and 33P) and added them to seawater samples of differing trophic status from coastal (mesotrophic) and offshore (oligotrophic) California waters and French Mediterranean waters (oligotrophic). Rates of degradation were determined by the loss of high molecular weight radiolabel over time and the fate of the degraded material (microbial uptake or accumulation in low molecular weight pools) was followed by size fractionation and/or acid extraction. Preliminary experiments with 3H-labeled, single-stranded RNA phage MS2 and marine phage H11/1 demonstrated that MS2 degraded significantly faster in coastal Santa Monica Bay seawater (2.5 ± 0.6% h-1), than the marine phage, H11/1 (0.99 ± 0.1% h-1). For labeled virus material from natural populations, rates of degradation were slower in oligotrophic waters (ranges from 1.0 to 3.3% h-1) than in mesotrophic waters (ranges from 4.9 to 6.0% h-1), corresponding to turnover rates of 1 to 4 d for this material. Degradation rates of labeled virus material are likely underestimates, because during preparation, degradation and uptake are continually occurring, resulting in accumulation of the less reactive products. The proportion of radiolabeled material taken up by microbes was greatest in oligotrophic waters, especially in the phosphate-limited Villefranche Bay, France, where most of the 33PO4-labeled material was taken up in less than 7 h. In contrast, the majority of degraded 3H-labeled material was not accumulated into biomass, and in 3 of 4 samples, accumulation was hardly detectable. The results suggest that viruses and lysis products are labile and turn over relatively rapidly, but often may not be efficiently incorporated into bacterial biomass. [TOP OF PAGE]

  112. The fates of viruses in the marine environment. Noble,R.T. (1999). University of Southern California. Viruses are an important component of the marine microbial food web, as they are capable of contributing to a significant fraction of the mortality of heterotrophic bacterioplankton. To better understand the ecological roles of viruses in the ocean and their possible influences upon biogeochemical cycles, I studied the fates of viruses in relation to other components of the microbial food web. the fates of viruses were studied by examining loss of infectivity, biochemical degradation, the effects of viral enrichment on bacterial mortality, and virus production. Spatio-temporal analysis of surface seawater of Santa Monica Bay over five years demonstrated significantly higher viral and bacterial abundances during the rainy season, with nearly constant virus to bacterial ratios of about 10. Loss of infectivity was studied with the use of eight laboratory cultured host/virus systems. The decay of infectivity of these viruses was assessed in seawater, and was partitioned according to singular causative agents of decay, such as ultraviolet light, heat labile material such as extracellular enzymes, and/or particles for adsorption. Virus isolates native to Santa Monica Bay consistently degraded more slowly in full sunlight than bacteriophages isolated from the North Sea, and although sunlight was an important contributing factor to virus decay, decay due to particles and dissolved substances in seawater was also significant. [TOP OF PAGE]

  113. The effects of viral enrichment on the mortality and growth of heterotrophic bacterioplankton. Noble,R.T., Middelboe,M., Fuhrman,J.A. (1999). Aquat. Microb. Ecol. 18:1-13. The direct effects of viral enrichments upon natural populations of marine viruses and bacteria were studied in seawater from Santa Monica Bay, CA, USA. Active virus concentrates, or control additions (ultrafiltered seawater or autoclaved virus concentrate) were added to 2 l incubations of protist-free seawater, and the effects were monitored for about 3 d. At the beginning of the experiments, the virus numbers reflected the expected addition of intact virus particles as determined by transmission electron microscopy (TEM). Subsequently, the mean frequency of visibly infected bacteria (FVIB; % bacteria which were visibly infected with 5 or more virus-like particles) was greater in the enriched incubations than in the controls. In controls, the estimated percent of bacteria that were infected remained constant at about 5 to 10% of the total bacterial population, but with active enrichment, 10 to 35% of the total bacterial population was infected at a given time. Therefore, by increasing the concentration of active viruses in seawater incubations we were able to increase the amount of bacterial mortality attributed to virus infection. Even with the presumed increase in bacterial mortality, the net increases in bacterial abundance in the samples that were enriched with active virus concentrate were higher than those seen in the controls. The viral abundance in bottles that were enriched with the active virus concentrate was significantly higher than that in the controls in Expts 2 and 3 (p < 0.05), but by the end of the experiments, viral abundances in the enriched incubations approached control levels. In Expts 1 and 2, rates of DOP hydrolysis were higher in the samples enriched with the active virus concentrate, and may have been due to an increase in the incidence of viral lysis. However, overall analysis of DCAA, DFAA, and DOP hydrolysis were quite variable and difficult to interpret. Results indicate that viral enrichment increased the incidence of bacterial infection and consequently stimulated the growth of subpopulations of non-infected heterotrophic bacterioplankton. [TOP OF PAGE]

  114. Microbial gene transfer: an ecological perspective. Paul,J.H. (1999). J. Mol. Microbiol. Biotechnol. 1:45-50. Microbial gene transfer or microbial sex is a means of exchanging loci amongst prokaryotes and certain eukaryotes. Historically viewed as a laboratory artifact, recent evidence from natural populations as well as genome research has indicated that this process may be a major driving force in microbial evolution. Studies with natural populations have taken two approaches-either adding a defined donor with a traceable gene to an indigenous community, and detecting the target gene in the indigenous bacteria, or by adding a model recipient to capture genes being transferred from the ambient microbial flora. However, both approaches usually require some cultivation of the recipient, which may result in a dramatic underestimation of the ambient transfer frequency. Novel methods are just evolving to study in situ gene transfer processes, including the use of green fluorescent protein (GFP)-marked plasmids, which enable detection of transferrants by epifluorescence microscopy. A transduction-like mechanism of transfer from viral-like particles produced by marine bacteria and thermal spring bacteria to Escherichia coli has been documented recently, indicating that broad host range transduction may be occurring in aquatic environments. The sequencing of complete microbial genomes has shown that they are a mosaic of ancestral chromosomal genes interspersed with recently transferred operons that encode peripheral functions. Archaeal genomes indicate that the genes for replication, transcription, and translation are all eukaryotic in complexity, while the genes for intermediary metabolism are purely bacterial. And in eukaryotes, many ancestral eukaryotic genes have been replaced by bacterial genes believed derived from food sources. Collectively these results indicate that microbial sex can result in the dispersal of loci in contemporary microbial populations as well as having shaped the phylogenies of microbes from multiple, very early gene transfer events. [see for full-text entry]. [TOP OF PAGE]

  115. An evaluation of the efficacy of a wastewater treatment plant. Poncetta,D., Maiello,A., Guidetti,L., Moiraghi,R.A. (1999). Ig. Mod. 112:1-15. Effectiveness of wastewater treatment systems for microbiological pollution removal is a significant hygienic-sanitary problem, principally for the evaluation of effects on basins where the depuration final effluents flow. This study aimed to verify, from a microbiological viewpoint, the effectiveness of the activated sludge depuration process of Verbania and the environmental impact that its effluent has in comparison with the Lago Maggiore waters it flows into. The bacteric pollution extent has been evaluated quantifying the presence of fecal pollution indicators (total and fecal coliforms, fecal streptococci), sulfite-reducing clostridia spores and the presence of pathogens bacteria (salmonella) through classic colony techniques (membrane filter, MPN and pour plate method). The presence of enterovirus and bacteriophages have also been detected through isolation on cell cultures and lysis plaques. The results indicate a substantial reduction of all detected microorganisms of at least 2 log after the activated sludge treatment, and at least 3 log after chloration, with the disappearance of bacteriophages and salmonella in many samples. Enterovirus detection, based on qualitative methods, gave positive results in 95% of samples collected at the entry to the plant, whereas at the exit 63,2% of the tested samples resulted positive for ECP and this percentage fell to 15,8% after disinfection treatment. The positive samples were confirmed by biological molecular techniques. The comparison of the microbiological features surveyed in the coastal waters where the treatment plant effluent flows before and after its coming into operation shows an improvement of hygienic conditions. This situation is probably was due to the discharged effluent quality and to the convey to the plant of built-up area wastewater, which, in the past, directly reached the lake without passing through any depuration treatment. [TOP OF PAGE]

  116. High bacterial diversity in permanently cold marine sediments. Ravenschlag,K., Sahm,K., Pernthaler,J., Amann,R. (1999). Appl. Environ. Microbiol. 65:3982-3989. A 16S ribosomal DNA (rDNA) clone library from permanently cold marine sediments was established. Screening 353 clones by dot blot hybridization with group-specific oligonucleotide probes suggested a predominance of sequences related to bacteria of the sulfur cycle (43.4% potential sulfate reducers). Within this fraction, the major cluster (19.0%) was affiliated with Desulfotalea sp. and other closely related psychrophilic sulfate reducers isolated from the same habitat. The cloned sequences showed between 93 and 100% similarity to these bacteria. Two additional groups were frequently encountered: 13% of the clones were related to Desulfuromonas palmitatis, and a second group was affiliated with Myxobacteria spp. and Bdellovibrio spp. Many clones (18.1%) belonged to the gamma subclass of the class Proteobacteria and were closest to symbiotic or free-living sulfur oxidizers. Probe target groups were further characterized by amplified rDNA restriction analysis to determine diversity within the groups and within the clone library. Rarefaction analysis suggested that the total diversity assessed by 16S rDNA analysis was very high in these permanently cold sediments and was only partially revealed by screening of 353 clones. [TOP OF PAGE]

  117. First report of a putative cyanophage, MC-1 of Microcoleus sp. Rosowski,J.R., Shaffer,J.J., Martin,E.L. (1999). Microsc. Microanalysis 5:1142-1143. [TOP OF PAGE]

  118. Use of the polymerase chain reaction and denaturing gradient gel electrophoresis to study diversity in natural virus communities. Short,S.M., Suttle,C.A. (1999). Hydrobiologia 401:19-32. Viruses are abundant members of marine and freshwater microbial communities, and are important players in aquatic ecology and geochemical cycles. Recent methodological developments have allowed the use of the polymerase chain reaction (PCR) to examine the diversity of natural communities of viruses without the need for culture. DNA polymerase genes are highly conserved and are, therefore, suitable targets for PCR analysis of microbes that do not encode rRNA. As natural virus communities are largely made up of dsDNA viruses, and as many dsDNA algal viruses encode their own DNA polymerase, PCR primers can be designed to amplify fragments of these genes. This approach has been used to examine the genetic diversity in natural communities of viruses that infect phytoplankton. Algal-virus-specific primers were used to amplify polymerase fragments from natural virus samples, demonstrating the presence of a diverse community of viruses closely related to those that are known to infect phytoplankton. We have modified this approach by using denaturing gradient gel electrophoresis (DGGE) to rapidly analyze PCR products. DGGE will permit rapid and efficient fingerprinting of natural marine viral communities, and allow spatial and temporal differences in viral community structure to be examined. This paper provides a brief overview of how PCR and DGGE can be used to examine diversity in natural viral communities drawing on viruses that infect phytoplankton as an example. [TOP OF PAGE]

  119. Sunlight inactivation of fecal bacteriophages and bacteria in sewage-polluted seawater. Sinton,L.W., Finlay,R.K., Lynch,P.A. (1999). Appl. Environ. Microbiol. 65:3605-3613. Sunlight inactivation rates of somatic coliphages, F-specific RNA bacteriophages (F-RNA phages), and fecal coliforms were compared in seven summer and three winter survival experiments. Experiments were conducted outdoors, using 300-liter 2% (vol/vol) sewage-seawater mixtures held in open-top chambers. Dark inactivation rates (k(D)s), measured from exponential survival curves in enclosed (control) chambers, were higher in summer (temperature range: 14 to 20 degrees C) than in winter (temperature range: 8 to 10 degrees C). Winter k(D)s were highest for fecal coliforms and lowest for F-RNA phages but were the same or similar for all three indicators in summer. Sunlight inactivation rates (k(S)), as a function of cumulative global solar radiation (insolation), were all higher than the k(D)s with a consistent k(S) ranking (from greatest to least) as follows: fecal coliforms, F-RNA phages, and somatic coliphages. Phage inactivation was exponential, but bacterial curves typically exhibited a shoulder. Phages from raw sewage exhibited k(S)s similar to those from waste stabilization pond effluent, but raw sewage fecal coliforms were inactivated faster than pond effluent fecal coliforms. In an experiment which included F-DNA phages and Bacteroides fragilis phages, the k(S) ranking (from greatest to least) was as follows: fecal coliforms, F-RNA phages, B. fragilis phages, F-DNA phages, and somatic coliphages. In a 2-day experiment which included enterococci, the initial concentration ranking (from greatest to least: fecal coliforms, enterococci, F-RNA phages, and somatic coliphages) was reversed during sunlight exposure, with only the phages remaining detectable by the end of day 2. Inactivation rates under different optical filters decreased with the increase in spectral cutoff wavelength (50% light transmission) and indicated that F-RNA phages and fecal coliforms are more susceptible than somatic coliphages to longer solar wavelengths, which predominate in seawater. The consistently superior survival of somatic coliphages in our experiments suggests that they warrant further consideration as fecal, and possibly viral, indicators in marine waters. [TOP OF PAGE]

  120. An in situ enclosure experiment to test the solar UVB impact on plankton in a high altitude mountain lake: II) effects on the microbial food web. Sommaruga,R., Sattller,B., Oberleiter,A., Wille,A., Sommaruga-Wögrath,S., Psenner,R., Felip,M., Camarero,L., Pina,S., Gironés,R., Catalán,J. (1999). J. Plankton. Res. 21:859-879. We studied the impact of ambient levels of solar UVB radiation on the planktonic microbial food web (viruses, heterotrophic bacteria, heterotrophic flagellates and ciliates) of a high-mountain lake (2417 m above sea level) under in situ conditions for 16 days. Enclosures of 1 m3 receiving either the full sunlight spectrum or sunlight without UVB radiation were suspended at the lake surface. We found that the abundance of heterotrophic flagellates was always lower in the +UVB treatment than in the -UVB one. In addition, bacterial consumption, measured by the disappearance of fluorescently labelled bacteria, was significantly (p<0.05) reduced in the +UVB treatment. The abundance of non-filamentous bacteria (<10 µm long) was also lower in the +UVB treatment, suggesting a direct effect of UVB on their growth. This was supported by the significantly (p<0.05) lower cell-specific activity ([3H]-thymidine incorporation) found on the fifth day of the experiment. In contrast, UVB radiation had no effect on filamentous bacteria (>10 µm long) that represented only a small fraction of the total abundance (<4%) but up to ~70 % of the total bacterial biovolume. Ciliates, mainly Urotricha pelagica and U. furcata, were less impacted by UVB radiation although the net growth rate during the first week of the experiment was lower in the +UVB treatment than in the -UVB one (0.22 and 0.39 d-1, respectively). The abundance of virus-like particles during the first week of the experiment was higher in the -UVB treatment. After reaching the maximum value for the interaction viruses x bacteria, their number decreased dramatically (by ~85%) in both treatments with a decay rate of ~0.017 h-1. This study illustrates the complexity in assessing the impact of UVB radiation when more than one trophic level is considered and indicates the existence of different sensitivity to UVB radiation among components of the microbial food web. [TOP OF PAGE]

  121. (Methodic approaches to studing marine bacteria and viruses interaction) Metodicheskie podkhody k izucheniyu protsessa vzaimodejstviya morskikh bakterij i virusov. Stepanova,O.A., Shaida,V.G. (1999). Ehkologiya morya. Kiev [Ehkol. Morya] 48:96-99. Comparative study of interaction between marine bacteria and viruses with the employment of microcalorimetry and Bioscreen-C automatic analyzer has demonstrated higher sensitivity of microcalorimetric method. Thus method permits studying the dynamics of virus -- bacterium interaction at the level of both lytic phage infection and a variety of enzymatic and other functions induced by lysogeny as the result of viral deoxyribonucleic acid integration into bacterial. [TOP OF PAGE]

  122. Do viruses control the oceans? Suttle,C.A. (1999). Nat. His. 108:48-51. The thousands of pinpoints of light against the blackness made it easy to imagine I was in a spaceship traveling through the far reaches of the galaxy. What I was looking at were not stars, however, but the DNA of viruses in seawater, magnified a thousand times and glowing under the blue light of the epifluorescence microscope. Observations on the abundance and dynamics of such virus particles have been changing our understanding of the world's oceans. [TOP OF PAGE]

  123. Giant viruses infecting algae. van Etten,J., Meints,R.H. (1999). Ann. Rev. Microbiol. 53:447-494. Paramecium bursaria chlorella virus (PBCV-1) is the prototype of a family of large, icosohedral, plaque-forming, double-stranded-DNA-containing viruses that replicate in certain unicellular, eukaryotic chlorella-like green algae. DNA sequence analysis of its 330,742-bp genome leads to the predicition that this phycodnavirus has 376 protein encoding genes and 10 transfer RNA genes. The predicited gene products of ~40% of these genes resemble proteins of known function. the chlorella viruses have other features that distinguish them from most viruses, in addition to thier large genome size. These feature include: (a) The viruses encode multiple DNAmethyltransferases and DNA site-specific endonucleases; (b) PBCV-1 encodes at least part, if not the entire machinery to glycosylate its proteins; (c) PBCV-1 has a tleast two types of introns-a self-splicing intron in a transcription factor-like gene and a splicesomal processed type of intron in its DNA polymerase gene. Unlike the chlorella viruses, large double-stranded-DNA-containing viruses that infect marine, filamentous brown algae have a circular genome and a lysogenic phase in their life cycle. [TOP OF PAGE]

  124. Changes in bacterial and eukaryotic community structure after mass lysis of filamentous cyanobacteria associated with viruses. van Hannen,E.J., Zwart,G., van Agterveld,M.P., Gons,H.J., Ebert,J., Laanbroek,H.J. (1999). Appl. Environ. Microbiol. 65:795-801. During an experiment in two laboratory-scale enclosures filled with lake water (130 liters each) we noticed the almost-complete lysis of the cyanobacterial population. Based on electron microscopic observations of viral particles inside cyanobacterial filaments and counts of virus-like particles, we concluded that a viral lysis of the filamentous cyanobacteria had taken place. Denaturing gradient gel electrophoresis (DGGE) of 16S ribosomal DNA fragments qualitatively monitored the removal of the cyanobacterial species from the community and the appearance of newly emerging bacterial species. The majority of these bacteria were related to the Cytophagales and actinomycetes, bacterial divisions known to contain species capable of degrading complex organic molecules. A few days after the cyanobacteria started to lyse, a rotifer species became dominant in the DGGE profile of the eukaryotic community. Since rotifers play an important role in the carbon transfer between the microbial loop and higher trophic levels, these observations confirm the role of viruses in channeling carbon through food webs. Multidimensional scaling analysis of the DGGE profiles showed large changes in the structures of both the bacterial and eukaryotic communities at the time of lysis. These changes were remarkably similar in the two enclosures, indicating that such community structure changes are not random but occur according to a fixed pattern. Our findings strongly support the idea that viruses can structure microbial communities. [TOP OF PAGE]

  125. Lysogeny and prophage induction in coastal and offshore bacterial communities. Weinbauer,M.G., Suttle,C.A. (1999). Aquat. Microb. Ecol. 18:217-225. The influence of solar radiation and hydrogen peroxide on induction of lysogens, and the resulting effect on bacteriophage production and bacterial mortality was investigated for coastal and oceanic marine bacterial communities at 6 stations in the western Gulf of Mexico. The percentage of lysogenic cells induced by mitomycin C was also determined. Solar radiation and hydrogen peroxide were not as effective as mitomycin C at inducing phage production. The burst size of cells induced by mitomycin C was estimated by transmission electron microscopy, assuming that cells completely filled with viral particles were on the verge of bursting. The smallest estimates of burst size were associated with oligotrophic oceanic stations and ranged from 15 to 28 viruses produced per lytic event, while in more productive coastal waters the estimated burst sizes ranged from 33 to 64. The mitomycin C-induced phage production and burst size were used to estimate the number of lysogenic bacterial cells. On average, the percentage of inducible lysogens was higher at offshore (1.5 to 11.4%) than at coastal (0.8 to 2.2%) stations. However, with the exception of 1 station, less than 5% of the bacteria could be induced to produce phage, suggesting that lysogens only occasionally comprised a significant component of these bacterial communities. The proportion of lysogens that could be induced by sunlight, relative to those that could be induced by mitomycin C, was lower at oceanic than coastal stations. This implies that prophages in optically transparent offshore waters were more resistant to induction by solar radiation, or that most lysogens that could be triggered by sunlight were already induced. Based on a steady-state model, induction of lysogenic bacteria by solar radiation or hydrogen peroxide could result in between 0 and 3.5% or 0.9 and 3.4% of the total bacterial mortality, respectively. Our results imply that solar radiation and hydrogen peroxide induced lysogenic phage production were not an important source of phage production or bacterial mortality in offshore or coastal waters of the western Gulf of Mexico. [TOP OF PAGE]

  126. Sunlight-induced DNA damage and resistance in natural viral communities. Weinbauer,M.G., Wilhelm,S.W., Suttle,C.A., Pledger,R.J., Mitchell,D.L. (1999). Aquat. Microb. Ecol. 17:111-120. Using a highly specific radioimmunoassay, the sunlight-induced formation of cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts ([6-4] PPs) in viral DNA was investigated for natural virus communities in offshore and coastal waters of the western Gulf of Mexico as well as for clonal viral isolates. Concentrations of (6-4) PPs were consistently lower than CPD concentrations, and ranged from 1.5 to 17.0% of total measured photodamage. The accumulation of photoproducts varied among the natural viral community, the marine Vibrio phage PWH3a-P1 and the Synechococcus sp. DC2 (WH7803) cyanophage SYN-M3, which were deployed in situ from dawn until dark. Natural viral communities were more resistant to DNA damage than the cyanophage isolate SYN-M3, which was more resistant to damage than bacteriophage PWH3a-P1. Moreover, depth profiles revealed that photodamage in viral isolates deployed in the water column accumulated more rapidly at offshore stations than at coastal stations. In natural virus communities collected from offshore surface waters, photodamage accumulated during the solar day with maximum damage occurring between 15:00 and 18:00 h. Depth profiles obtained during calm seas showed that photodamage concentrations were high in surface waters at the offshore stations and at 1 coastal station. Results at other coastal stations undergoing significant mixing demonstrated no photoproduct accumulations. Results demonstrate that natural virus communities were more tolerant to DNA damaging radiation than the laboratory isolates used in this study. Consequently, laboratory isolates can be poor proxies for UV impacts on natural viral communities. [TOP OF PAGE]

  127. Analysis of cyanophage diversity and population structure in a south-north transect of the Atlantic ocean. Wilson,W., Fuller,N., Joint,I., Mann,N. (1999). Bull. Inst. Océanogr. Manaco 19:209-216. [TOP OF PAGE]

  128. Analysis of cyanophage diversity and population structure in a south-north transect of the Atlantic ocean. Wilson,W.H., Fuller,N.J., Joint,I.R., Mann,N.H. (1999). Bull. Inst. Océanogr. Manaco 0:209-216. Cyanophages (viruses which infect cyanobacteria) are abundant in the marine environment and are thought to be a significant factor in determining the dynamics of Synechococcus spp. populations. In an effort to use molecular techniques to characterise cyanophage populations, we designed cyanophage-specific (CPS) PCR primers based on a gene found in three genetically distinct marine cyanophages (Fuller et al., 1998). CPS primers were used to amplify cyanophage DNA extracted from viral communities concentrated from sea-water samples obtained during a cruise transect between the Falkland Islands, in the south Atlantic ocean, to the UK. Following phylogenetic analysis of cloned and sequenced PCR products, it was revealed that genetic diversity of marine cyanophage clones within a single water sample was as great as clones and cyanophage isolates collected between different oceans. Denaturing gradient gel electrophoresis (DGGE) analysis confirmed this high diversity. DGGE analysis also revealed changes in cyanophage population structure in surface seawater over the south-north transect and throughout depth profiles in the water column. Maximum Synechococcus spp. concentrations, in a stratified water column, correlated with maximum cyanophage diversity. [TOP OF PAGE]

  129. Characterization of a Vibrio parahaemolyticus phage isolated from marine. Yoon,S.O., Ju,S.A., Heo,M.S., Jung,C.R., Ju,J.W. (1999). Journal of the Korean Society for Microbiology 34:423-433. A novel bacteriophage, designated as VPP97, that infects the strains of Vibiro parahaemolyticus (hallophilic, Gram-negative bacterium) isolated most commonly from marine environments, has been discovered, and several of its properties have been determined. The plaques were clear and sized 0.6-1.0 mm in diameter. The virion forms a single band on 70% sucrose gradient and p1.50 CsCl gradient by sucrose gradient centrifugation and CsCl gradient centrifugation respectively. It has a hexagonal head and a relatively long tail, as shown by electron microscopy. Vibrio alginolyticus, Vibrio fluvialis and Vibrio furnissii were also sensitive to this phage It was almost totally inactivated at 70ºC and at pH below 5 or over 10. The nucleic acid of VPP97 is composed of DNA. The VPP97 had 9 specific structural proteins sized between 21.5 kDa and 97.4 kDa on SDS-PAGE. When V. parahaemolyticus cultures were treated with either phage VPP97 or one of the several antibiotics for 2 hours, the viable number of V. parahaemolyticus treated with the phage VPP97 is lower than that treated with chloramphenicol, erythromycin or penicillin, but not lower than that treated with tetracycline. Mice that have responded to the phage treatment revealed the lower numbers of V. parahaemolyticus in small intestine and less damage on small intestine compared to the untreated mice. Therefore, we suggest that the phage treatment appears effective to the infection by V. parahaemolyticus. [TOP OF PAGE]

  130. Blue-green algal viruses (cyanophages). Zhao,Y., Shi,Z., Huang,G., Wang,X. (1999). Virologica Sinica 14:100-105. [TOP OF PAGE]

  131. Horizontal Gene Transfer. Anonymous (1998). Chapman & Hall, New York.[TOP OF PAGE]

  132. Dissolved esterase activity as a tracer of physoplankton lysis: Evidence of high phytoplankton lysis rates in the northwestern Mediteranean. Agustí,S., Satta,M.P., Mura,M.P., Benavent,E. (1998). Limnol. Oceanogr. 43:1836-1849. Phytoplankton cell lysis is perceived to be an important loss process in the sea, although a quantification of this process has proved elusive. A recently developed method, based on the measurement of dissolved esterase activity (EA), was used to estimate the release of esterases following phytoplankton cell lysis in an effort to evaluate the importance of this process as a loss factor in the summer phytoplankton of the northwestern Mediterranean Sea. Implicit in this method was the assumption that only the lysis of phytoplankton cells caused these enzymes to be released to the medium. This assumption was tested by analyzing the presence and release of esterases by marine bacteria, heterotrophic flagellates, and heterotrophic ciliates, all isolated from the Blanes Bay (northwestern Mediterranean, Spain), and by phytoplankton grown in culture (Synechococcus elongatus, Dunaliella sp., Chlorella sp., Phaeodactyllum tricornutum, and Chaetoceros decipiens). The dissolved EA found during the growth, stationary, and decay phases of microheterotrophs (bacteria, flagellate, and ciliate) was negligible when compared to that found for phytoplanktonic cultures. Differences in cell volume explained the differences in cell EA among the organisms, but heterotrophs showed lower cell EA (10-50-fold) than phytoplanktonic cells of similar cell size. These results support the assumption that microheterotrophs do not contribute significant amounts of EA to the dissolved pear, allowing the use of the method to estimate phytoplankton lysis. Independent estimates of cell, loss in phytoplankton cultures, derived from cell cycle analysis, confirmed the estimates of cell lysis obtained from the measurement of dissolved EA.

    During the study conducted in the Mediterranean Sea, the water column was strongly stratified, showing a deep (40-55 m) chlorophyll a (Chl a) maximum (DCM; 1.25 +/- 0.09 mu g liter-1) and low surface Chl a concentrations (0.09 +/- 0.008 mu g liter(-1)). Phytoplankton lysis rates ranged between 0.026 d-1 and 1.9 d-1, and they declined significantly with depth; the fastest rates were found in surface waters and the slowest ones at the DCM. Despite the fast gross growth rates of surface phytoplankton las calculated from phytoplankton biovolume and oxygen production), the calculated lysis rates represented a considerable proportion of gross phytoplankton growth rate (50%) at the surface, whereas they were comparatively less important at the DCM (7%). These results provide strong evidence that phytoplankton lysis can be an important loss factor in the surface waters of this stratified, oligotrophic sea. Phytoplankton lysis could provide the loss factor needed to explain the low phytoplankton biomass despite fast growth and low grazing rates in the northwestern Mediterranean surface waters. The high lysis rate of phytoplankton in surface waters represents an important path by which primary production may fuel the growth of microheterophic organisms, consistent with the high respiration rate of the surface community examined. The conclusion that phytoplankton lysis rates can occur at rates high enough to influence food web dynamics and biogeochemical cycles in the oligotrophic ocean should stimulate research on this largely neglected loss factor in phytoplankton ecology. [TOP OF PAGE]

  133. Modeling and analysis of a marine bacteriophage infection. Beretta,E., Kuang,Y. (1998). Math. Biosci. 149:57-76. A mathematical model for the marine bacteriophage infection is proposed and its essential mathematical features are analyzed. Since bacteriophage infection induces bacterial lysis which releases into the marine environment, on the average, 'b' viruses per cell, the parameter b epsilon (1, t infinity) or 'virus replication factor' is chosen as the main parameter on which the dynamics of the infection depends. We proved that a threshold b* exists beyond which the endemic equilibrium bifurcates from the free disease one. Still, for increasing b values the endemic equilibrium bifurcates toward a periodic solution. We proved that a compact attractor set omega within the positive cone exists and within omega the free disease equilibrium is globally stable whenever b < or = b*, whereas it becomes a strong uniform repeller for b > b*. A concluding discussion with numerical simulation is then presented. [TOP OF PAGE]

  134. Virus production in Phaeocystis pouchetii and its relation to host cell growth and nutrition. Bratbak,G., Jacobsen,A., Heldal,M., Nagasaki,K., Thingstad,T.F. (1998). Aquat. Microb. Ecol. 16:1-9. In this experimental study we investigated how growth conditions and physiological status of the marine haptophyte Phaeocystis pouchetii affect its interaction with the lytic virus PpV01. A simple mathematical model describing the infection, the lysis of algae and the production of new viral particles was developed as an aid for analyzing and understanding the interaction between host and virus. P. pouchetii was susceptible to virus infection in all stages of growth. Nutrient or light limitation of algal growth did not inhibit viral reproduction and cell lysis. Neither the infectivity of the progeny viruses produced nor the length of the lytic cycle appeared to be affected by the host cells' growth condition. However, possible effects may have been obscured by low accuracy of infective virus counts or by low sampling frequency. The host cells' growth conditions did have a significant impact on burst size. A maximum of 510 viruses produced per infected host cell was found in exponentially growing cultures, while low burst size (minimum 15) was found in stationary phase cultures, in nutrient depleted cultures and in light limited cultures. [TOP OF PAGE]

  135. Viral lysis of Phaeocystis pouchetii and bacterial secondary production. Bratbak,G., Jacobsen,A., Heldal,M. (1998). Aquat. Microb. Ecol. 16:11-16. In this experimental study we investigated the effect of viral infection on primary production and carbon now in a phytoplankton-DOC-bacteria food chain during viral lysis of the phytoplankton population. The phytoplankter host-virus system used was Phaeocystis pouchetii (Prymnesiophyceae) and the virus PpV01. Viral infection allowed primary production in the cells to continue throughout most of the lytic cycle. In non-infected algal cultures, net production of DOC and bacterial biomass was low and at the end of the experiment the DOC concentration was 10 to 20%, and the bacterial biomass 0.5 to 4 % of the algal carbon biomass. The amount of DOC released during viral lysis of the algal cells implies that the entire algal biomass was converted to DOG. Growth of bacteria succeeding cell lysis and release of DOC in Virus infected cultures demonstrated that the net effect of the virus infection was an efficient conversion of algal biomass into bacterial biomass. [TOP OF PAGE]

  136. Occurrence of male-specific bacteriophage in feral and domestic animal wastes, human feces, and human-associated
    wastewaters. Calci,K.R., Burkhardt,W.3., Watkins,W.D., Rippey,S.R. (1998). Appl. Environ. Microbiol. 64:5027-5029
    . Male-specific bacteriophage (MSB) densities were determined in animal and human fecal wastes to assess their potential impact on aquatic environments. Fecal samples (1,031) from cattle, chickens, dairy cows, dogs, ducks, geese, goats, hogs, horses, seagulls, sheep, and humans as well as 64 sewerage samples were examined for MSB. All animal species were found to harbor MSB, although the great majority excreted these viruses at very low levels. The results from this study demonstrate that in areas affected by both human and animal wastes, wastewater treatment plants are the principal contributors of MSB to fresh, estuarine, and marine waters. [TOP OF PAGE]

  137. Fecal coliform-related bacterial and coliphage populations in five lakes of southeastern Spain. Calvo,C., Gomez,M.A., Gonzalez-Lopez,J. (1998). Microbiological Research 153:283-288. Aerobic heterotrophic bacteria, fecal and total coliforms, fecal streptococci and coliphages were isolated from five protected lakes in the Antequera area of Spain over the time from January to March (1994-96). The water samples contained large number of heterotrophic bacteria (mean counts 0.2 to 5.0 x 10(7) cfu per 100 ml). Most of the lakes contained fecal streptococci and a relationship between streptococci and salinity of the water samples was established. Coliphages were isolated from lakes containing fecal coliform and these bacteria were taxonomically identified as E. coli. Coliform bacilli do not seem to be an adequate indicator of fecal pollution for these ephemeral small lakes. [TOP OF PAGE]

  138. Prophage induction of indigenous marine lysogenic bacteria by environmental pollutants. Cochran,P.K., Kellogg,C.A., Paul,J.H. (1998). Mar. Ecol. Prog. Ser. 164:125-133. Lysogenic bacteria may be abundant components of bacterial assemblages in marine waters. The tremendous number of viruses found in estuarine and other eutrophic environments may be the result in part of induction of prophages. Mitomycin C is the inducing agent of choice for prophage induction; however this is not naturally found in the marine environment. We determined the capability of environmentally important pollutants to effect prophage induction in natural populations of marine bacteria. We investigated Aroclor 1248, a PCB mixture, bunker C fuel oil No. 6, and a pesticide mixture as inducing agents for natural bacterial communities from the Gulf of Mexico. Mitomycin C was also employed as a positive control for induction. Induction was determined as a significant increase in viral direct counts compared to control and ranged from 149 to 1336% of the controls. Two-thirds of the environments sampled showed prophage induction by one of the methods utilized, with the PCB mixture and Aroclor 1248 giving the highest percent efficiency (75%) of induction. This study shows that many environmentally important pollutants may be inducing agents for natural lysogenic viral production in the marine environment. [TOP OF PAGE]

  139. Occurrence of a sequence in marine cyanophages similar to that of T4 gp20 and its application to PCR-based detection and quantification techniques. Fuller,N.J., Wilson,W.H., Joint,I.R., Mann,N.H. (1998). Appl. Environ. Microbiol. 64:2051-2060. Viruses are ubiquitous components of marine ecosystems and are known to infect unicellular phycoerythrin-containing cyanobacteria belonging to the genus Synechococcus. A conserved region from cyanophage genome was identified in three genetically distinct cyanomyoviruses, and a sequence analysis revealed that this region exhibited significant similarity to a gene encoding a capsid assembly protein (gp20) from the enteric coliphage T4. The results of a comparison of gene 20 sequences from three cyanomyoviruses and T4 allowed us to design two degenerate PCR primers, CPS1 and CPS2, which specifically amplified a 165-bp region from the majority of cyanomyoviruses tested. A competitive PCR (cPCR) analysis revealed that cyanomyovirus strains should be accurately enumerated, and it was demonstrated that quantification was log-linear over ca. 3 orders of magnitude. Different calibration curves were obtained for each of the three cyanomyovirus strains tested; consequently, cPCR performed with primers CPS1 and CPS2 could lead to substantial inaccuracies in estimates of phage abundance in natural assemblages. Further sequence analysis of cyanomyovirus gene 20 homologs would be necessary in order to design primers which do not exhibit phage-to-phage variability in priming efficiency. It was demonstrated that PCR products of the correct size could be amplified from seawater samples following 100x concentration and even directly without any prior concentration. Hence, the use of degenerate primers in PCR analysis of cyanophage populations should provide valuable data on the diversity of cyanophages in natural assemblages. Further optimization of procedures may ultimately lead to a sensitive assay which can be used to analyze natural cyanophage populations both quantitatively (by cPCR) and qualitatively following phylogenetic analysis of amplified products. [TOP OF PAGE]

  140. Characterization of a lytic virus infectious to the bloom-forming microalga Aureococcus anophagefferens (Pelagophyceae). Garry,R.T., Hearing,P., Cosper,E.M. (1998). J. Phycol. 34:616-621. Aureococcus anophagefferens Hargraves and Sieburth has caused recurring monospecific blooms in Long Island embayments since it was first described in 1985. It was termed the “brown tide,” due to the resulting water color, and has had a devastating effect on Long Island's (New York) marine ecosystem. In 1992, a virus that was capable of causing lysis of A. anophagefferens was isolated and maintained in culture. We report on the further characterization of this virus, Aureococcus anophagefferens virus-1 (AaV-1), indicated by a buoyant density of 1.2776 g times mL super(-1) in a CsCl equilibrium gradient. Electron microscopy revealed a phage with a hexagonal head and tail similar to previously described phages. By using adenovirus for calibration, the virus was found to have a head 50-55 nm wide and a tail 70-75 nm long. The viral band was infectious to A. anophagefferens after dialysis. The virus was composed of at least 16 distinct polypeptides ranging in molecular weight from 20 to 230 kDa. The adsorption coefficient for the virus was 7.2 x 10 super(-9) mL times min super(-1), and the burst size was calculated to be 9.4 viruses per A. anophagefferens cell at 20 degree C. Complete lysis of A. anophagefferens occurred with a titer as low as 893 viruses times mL super(-1), and the lower limit of infectivity was 93 viruses times mL super(-1). The virus lost its infectivity between 30 degree and 40 degree C. These results suggest that AaV-1 is highly infectious and that the role of the virus in preventing or ending A. anophagefferens blooms needs further investigation. [TOP OF PAGE]

  141. The effect of cyanophages on the morality of Synechococcus spp. and selection for UV resistant viral communities. Garza,D.R., Suttle,C.A. (1998). Microb. Ecol. 36:281-292. Viruses that cause lysis of Synechococcus spp. are present throughout the year in the western Gulf of Mexico. The effect of sunlight on loss rates of cyanophage infectivity was determined by incubating natural cyanophage communities and cyanophage isolates (strains S-PWM1 and S-PWM3) in UV-transparent bags at the surface, and at depth, on several occasions throughout the year. Decay rates of infectivity of natural cyanophage communities at the surface, at Port Aransas, Texas, USA, ranged from undetectable to 0.335 h(-1), with the highest rates occurring during the summer. During the spring and winter, decay rates of cyanophage isolates and natural cyanophage communities were generally similar, but during summer, decay rates of isolates were as much as twofold higher than the natural communities. In situ incubations at two offshore stations during a bloom of Synechococcus spp. produced decay rates of 0.53 and 0.75 d(-1), integrated over the mixed layer and averaged over 24 h. Based on a burst size of 81 viruses produced per lysed cell (measured for natural cyanobacterial communities in the Gulf of Mexico), cyanophages imposed mortality rates of 1 and 8%, respectively, on Synechococcus spp. In contrast, in nearshore incubations in the winter and spring, cyanophages were responsible for removing <1% of the Synechococcus cells on a daily basis. Only an estimated 2 to 3% of contacts led to viral infections (based on theoretical contact rates between host cells and cyanophages, and estimates of cyanophage mortality), regardless of the time of year or concentrations of viruses and hosts. These results indicate that natural cyanophage communities tolerate damage by solar radiation better in summer than in winter. Moreover, net decay rates of cyanophage infectivity in sunlight were similar, whether host cells were present or not, indicating that detectable cyanophage production did not occur during daytime in situ incubations. [TOP OF PAGE]

  142. Virus-mediated total release of dimethylsulfonioproprionate from marine phytoplankton: a potential climate process. Hill,R.W., White,B.A., Cottrell,M.T., Dacey,J.W.H. (1998). Aquat. Microb. Ecol. 14:1-6. Growing, axenic cultures of the eukaryotic marine microalga Micromonas pusilla (Prasinophyceae) were inoculated with 0.7 infectious particles cell(-1) of the viral pathogen MPV (Micromonas pusilla virus). Starting 11 to 14 h after the inoculation, rapid release of intracellular dimethylsulfoniopropionate (DMSP) to the dissolved pool occurred along with cell lysis. DMSP release was total. Release facilitates bacterial degradation of DMSP to dimethylsulfide, a gas that affects cloud cover over the oceans. Viruses of eukaryotic marine phytoplankton may thus participate in the biological shaping of global climate. [TOP OF PAGE]

  143. Gene transfer by transduction in the marine environment. Jiang,S.C., Paul,J.H. (1998). Appl. Environ. Microbiol. 64:2780-2787. To determine the potential for bacteriophage-mediated gene transfer in the marine environment, we established transduction systems by using marine phage host isolates. Plasmid pQSR50, which contains transposon Tn5 and encodes kanamycin and streptomycin resistance, was used in plasmid transduction assays. Both marine bacterial isolates and concentrated natural bacterial communities were used as recipients in transduction studies. Transductants were detected by a gene probe complementary to the neomycin phosphotransferase (nptII) gene in Tn5. The transduction frequencies ranged from 1.33 X 10-7 to 5.13 X 10-9 transductants/PFU in studies performed with the bacterial isolates. With the mixed bacterial communities, putative transductants were detected in two of the six experiments performed. These putative transductants were confirmed and separated from indigenous antibiotic-resistant bacteria by colony hybridization probed with the nptII probe and by PCR amplification performed with two sets of primers specific for pQSR50. The frequencies of plasmid transduction in the mixed bacterial communities ranged from 1.58 X 10-8 to 3.7 X 10-8 transductants/PFU. Estimates of the transduction rate obtained by using a numerical model suggested that up to 1.3 X 1014 transduction events per year could occur in the Tampa Bay Estuary. The results of this study suggest that transduction could be an important mechanism for horizontal gene transfer in the marine environment. [TOP OF PAGE]

  144. Characterization of marine temperate phage-host systems isolated from Mamala Bay, Oahu, Hawaii. Jiang,S.C., Kellogg,C.A., Paul,J.H. (1998). Appl. Environ. Microbiol. 64:535-542. To understand the ecological and genetic role of viruses in the marine environment, it is critical to know the infectivity of viruses and the types of interactions that occur between marine viruses and their hosts. We isolated four marine phages from turbid plaques by using four indigenous bacterial hosts obtained from concentrated water samples from Mamala Bay, Oahu, Hawaii. Two of the rod-shaped bacterial hosts were identified as Sphingomonas paucimobilis and Flavobacterium sp. All of the phage isolates were tailed phages and contained double-stranded DNA. Two of the phage isolates had morphologies typical of the family Siphoviridae, while the other two belonged to the families Myoviridae and Podoviridae. The head diameters of these viruses ranged from 47 to 70.7 nm, and the tail lengths ranged from 12 to 146 nm. The burst sizes ranged from 7.8 to 240 phage/bacterial cell, and the genome sizes, as determined by restriction digestion, ranged from 36 to 112 kb. The members of the Siphoviridae, T-f HSIC, and T-f D0, and the member of the Myoviridae, T-f D1B, were found to form lysogenic associations with their bacterial hosts, which were isolated from the same water samples. Hybridization of phage T-f HSIC probe with lysogenic host genomic DNA was observed in dot blot hybridization experiments, indicating that prophage T-f HSIC was integrated within the host genome. These phage-host systems are available for use in studies of marine lysogeny and transduction. [TOP OF PAGE]

  145. Significance of lysogeny in the marine environment: studies with isolates and a model of lysogenic phage production. Jiang,S.C., Paul,J.H. (1998). Microb. Ecol. 35:235-243. The importance of lysogeny in marine microbial populations is just beginning to be understood. To determine the abundance of lysogens in bacterial populations, we studied the occurrence of lysogenic bacteria among bacterial isolates from a variety of marine environments. More than 116 bacteria isolated on artificial seawater nutrient agar plates were tested for the presence of inducible prophage by mitomycin C and UV radiation. Induction was determined as a decrease in culture absorbance at 600 nm, after treatment with inducing agents. Samples in which optical density decreased or remained the same after induction were further examined by transmission electron microscopy, for the presence of virus-like particles. More than 40% of the bacterial isolates contained inducible prophage, as determined by mitomycin C induction. A higher percentage of lysogenic bacteria was found in isolates from oligotrophic environments, compared to coastal or estuarine environments. These studies suggest that lysogenic bacteria are important components in marine microbial populations. However, a mathematical model based on viral and bacterial abundance and production rates suggests that, under normal conditions, lysogenic viral production contributes less than 0.02% of total viral production. Therefore, lysogens in the marine environment may serve as a source of viruses and only contribute significantly to viral production during natural induction events. [TOP OF PAGE]

  146. Genetic diversity and DNA repair of marine vibriophages. Kellogg,C.A. (1998). University of South Florida, FL, USA. Viruses are the numerically dominant organisms in the global ocean. The objectives of this study investigate the dynamics of a marine bacteriophage species, the Phi 16-like vibriophages: (1) To determine the genetic diversity of vibriophage isolates from geographically diverse environments, (2) To enumerate this virus in a variety of environments and correlate the phage counts with a number of parameters, (3) To determine if the levels of spatial genetic diversity detected in the first study were comparable to the seasonal genetic variations occurring over a year at one local sampling site, (4) To study the host repair mechanisms which allow these viruses to survive inactivation by ultraviolet radiation. Sixty-nine vibriophages were isolated from waters surrounding Florida and Hawaii on Vibrio parahaemolyticus st. 16, and were determined by DNA hybridization to be genetically related. The Tampa Bay population of Phi 16-like vibriophages was positively correlated to temperature (r=0.669), but in other environments the phages also showed a dependence on bacterial abundance and a negative correlation to viral direct counts. The concentration of these phages varied seasonally in Tampa Bay, constituting a fraction of the total viral community ranging from 10-10 to 10-7. These viruses were primarily estuarine, although a few isolates have been found offshore and as deep as 1500 m. During the year-long genetic study in Tampa Bay, a 484 bp fragment was amplified from 165 isolates. The fragments were sorted into operational taxonomic units (OTUs) and representatives were sequenced. These sequences were compared to sequences of the geographic isolates. The genetic similarities ranged from 83% to 100%, showing that there was as much diversity temporally in Tampa Bay as there is spatially across all the sampling locations. Vibrio parahaemolyticus st. 16 clearly demonstrates photoreactivation and excision repair of the phages. Compared to V. parahaemolyticus HER1165 phages, the Phi 16-like vibriophages are more efficiently repaired, and have higher G+C contents. One HER1165 phage, which was most sensitive to UV damage and showed no photoreactivation (vp12) was found to have a G+C content of only 16%. All phage inactivation coefficients correlated with G+C content (r=0.955) suggesting that AT rich genomes are more UV sensitive. [TOP OF PAGE]

  147. Viruses in Antarctic lakes. Kepner,R.L., Wharton,R.A.Jr., Suttle,C.A. (1998). Limnol. Oceanogr. 43:1754-1761. Water samples collected from four perennially ice-covered Antarctic lakes during the austral summer of 1996-1997 contained high densities of extracellular viruses. Many of these viruses were found to be morphologically similar to double-stranded DNA viruses that are known to infect algae and protozoa. These constitute the first observations of viruses in perennially ice-covered polar lakes. The abundance of planktonic viruses and data suggesting substantial production potential (relative to bacterial secondary and photosynthetic primary production) indicate that viral lysis may be a major factor in the regulation of microbial populations in these extreme environments. Furthermore, we suggest that Antarctic lakes may be a reservoir of previously undescribed viruses that possess novel biological and biochemical characteristics. [TOP OF PAGE]

  148. Distribution of indicator bacteria and bacteriophages in shellfish and shellfish-growing waters. Legnani,P., Leoni,E., Lev,D., Rossi,R., Villa,G.C., Bisbini,P. (1998). J. Appl. Microbiol. 85:790-798. Shellfish (mussels and clams) and shellfish-growing waters were examined for indicator bacteria according to the EC regulations, Salmonella spp., coliphages and anti-Salmonella phages. Samples were collected both from natural-growing areas along the coast and from authorized shellfish-harvesting beds. The coastal area was affected by organic pollution and extensive faecal contamination and, according to the legal requirements, was unsuitable for shellfish farming. The shellfish collected along the coast also showed faecal contamination at levels which did not conform to legal standards. No significant differences were observed between the frequency of isolation of somatic coliphages and indicator bacteria from sea water. In contrast, both the authorized and wild coastal shellfish were contaminated by coliphages at a significantly higher level than the corresponding bacteria) indicators for faecal contamination (chi2 test, P < 0.01), waters (P < 0.001), and sediments (P < 0.05), but no correlation was found in shellfish, thus Coliphage concentrations were significantly correlated with faecal indicators in marine of economic importance. [TOP OF PAGE]

  149. Studies on the pustule disease of abalone (Haliotis discus hannai Ino) on the Dalian coast. Li,T., Ding,M., Zhang,J., Xiang,J., Liu,R. (1998). J. Shelfish Res. 17:707-711. Since first observed in the summer of 1993, a serious pustule disease has spread among several abalone hatcheries in the Dalian area. It affects different growth stages of the abalone. Mortality has been as high as 50-60%. Three strains of bacteria (D, T, and N) were obtained, isolated, and purified from the Aquacultural Company of Dalian (D), the Aquacultural Company of Precious Sea Food of the Pacific Ocean (T), and the Dalian New Harbor Aquacultural Company (N). Observation by electron microscopy showed that the three strains were all short rod bacteria with a single polar flagellum. They all grew in 1% tryptone water in the ranges, 15-42 degree C; salinity, 0-70ppt; and pH, 5.5-11. Physiological and biochemical analyses gave the same result as in an earlier study by the authors. The bacteriophage of the D strain, which was isolated by the authors (reported elsewhere) could propagate and replicate on the N and T strains. Thus, the three strains are concluded to belong to the same species of bacteria, one earlier identified as Vibrio fluvialis-II. Results of experimental trials indicated that the pustule disease is transmitted through lesions in the foot. Infection quickly followed intramuscular injection. Infection did not result when bacteria were included in the food or when present in the surrounding seawater. [TOP OF PAGE]

  150. Elevated production of dimethylsulfide resulting from viral infection of cultures of Phaeocystis pouchetii. Malin,G., Wilson,W.H., Bratbak,G., Liss,P.S., Mann,N.H. (1998). Limnol. Oceanogr. 43:1389-1393. [TOP OF PAGE]

  151. Evidence of pseudolysogeny in a marine phage host system. McLaughlin,M.R., Paul,J.H. (1998). Abstracts of the General Meeting of the American Society for Microbiology 98, 387-??? [TOP OF PAGE]

  152. Principles of virus-directed regulation of formation of the dynamic system virus-cell (problems, methodology and prospects of cyanophagia). Mendzhul,M.I., Lysenko,T.G., Koltukova,N.V., Syrchin,S.A., Sukhanov,S.N. (1998). Mikrobiol. Zh. 60:66-78. Dynamics of virus-directed regulation of formation of the complex virus - cell has been studied on the example of the system cyanophage-cyanobacterium. It is shown that in the process of virus reproduction the host-cell loses its own genetic apparatus, system of regulation of biosynthetic processes, reproductive ability and other functions of vital importance. As a matter of fact the formed virus - cell complex turns into powerful generator of nucleotides and amino acids for nonlimited synthesis of virus nucleic acids, proteins and morphogenesis of virions. The question is discussed concerning the possibility of the use of the system cyanophage cyanobacterium as the experimental models for development of functional unified model of productive infection, effective methods of prophylaxis and therapy of virus infections as well as the decision of various biotechnological problems. [TOP OF PAGE]

  153. [Key enzymes of biosynthesis of amino acids of the glutamic series in the virus-cell system Anabaena variabilis + A-1]. Mendzhul,M.I., Lysenko,T.G., Koltukova,N.V. (1998). Ukr Biokhim Zh 70:16-22. The influence of cyanophage A-1 reproduction on glutamate dehydrogenase (GDG) and glutamine synthetase (GS) in A. variabilis cells was studied. It was determined that the both enzymes are intensified by 70% and 30%, accordingly. Isoenzymes of GDG and GS were isolated from native and infected cells of cyanobacteria, they had various physicochemical properties. It is concluded that cyanophage development causes the specific modification of cell enzymes. [TOP OF PAGE]

  154. Intra-species host specificity of HaV (Heterosigma akashiwo virus) clones. Nagasaki,K., Yamaguchi,M. (1998). Aquat. Microb. Ecol. 14:109-112. 14 clones of the Heterosigma akashiwo virus (HaV) infecting the harmful bloom causing microalga Heterosigma akashiwo (Raphidophyceae) were isolated from coastal waters of Japan. Host specificities of the virus clones were tested against 18 strains of H. akashiwo isolated from coastal waters of the western part of Japan. Although all of the 14 virus clones lysed 10 of the H. akashiwo strains, in 4 strains no viral lysis was observed with any of the clones. The remaining 4 H. akashiwo strains were lysed by 7 to 11 of the virus clones. Further, viral lysis against H. akashiwo is not always complete, allowing the proliferation of surviving cells. These results indicate 2 possibilities: (1) HaVs are phenotypically diverse in terms of their host specificity; (2) H. akashiwo strains are phenotypically diverse in terms of their viral sensitivity. The high diversity among both the virus clones and the host strains concerning viral infection indicates that the interaction between virusesand hosts in situ appears more complicated than a simple host and pathogen relation. [TOP OF PAGE]

  155. Effect of temperature on the algicidal activity and the satability of HaV (Heterosigma akashiwo virus). Nagasaki,K., Yamaguchi,M. (1998). Aquat. Microb. Ecol. 15:211-216. The effect of temperature on the algicidal activity and stability of HaV (Heterosigma akashiwo virus), which infects the harmful bloom causing alga, H. akashiwo (Raphidophyceae), was determined by growing H. akashiwo culture inoculated with HaV under various conditions. Temperature and growth stage of the host culture are considered to be important factors determining the algicidal activity of HaV. The optimum temperature for the algicidal activity of HaV ranged from 20 to 25 degrees C. Comparing the viral susceptibility of H. akashiwo strains and the algicidal activity of the HaV clones at different temperatures, both were suggested to be phenotypically diverse. Effect of temperature on the stability of HaV was also evaluated. HaV showed a relatively rapid decrease in infectious titer even when preserved at 5 degrees C in the dark. The data is discussed in relation to the behavior of HaV in natural environments and the disintegration mechanism of H. akashiwo red tide. [TOP OF PAGE]

  156. Use of SYBR Green I for rapid epifluorescence counts of marine viruses and bacteria. Noble,R.T., Fuhrman,J.A. (1998). Aquat. Microb. Ecol. 14:113-118. A new nucleic acid stain, SYBR Green I, can be used for the rapid and accurate determination of viral and bacterial abundances in diverse marine samples. We tested this stain with formalin-preserved samples of coastal water and also from depth profiles (to 800 m) from sites 19 and 190 km offshore, by filtering a few ml onto 0.02 mu m pore-size filters and staining for 15 min. Comparison of bacterial counts to those made with acridine orange (AO) and virus counts with those made by transmission electron microscopy (TEM) showed very strong correlations. Bacterial counts with AO and SYBR Green I were indistinguishable and almost perfectly correlated (r super(2) = 0.99). Virus counts ranged widely, from 0.03 to 15 x 10 super(7) virus ml super(-1). Virus counts by SYBR Green I were on the average higher than those made by TEM, and a SYBR Green I versus TEM plot yielded a regression slope of 1.28. The correlation between the two was very high with an r super(2) value of 0.98. The precision of the SYBR Green I method was the same as that for TEM, with coefficients of variation of 2.9%. SYBR Green I stained viruses and bacteria are intensely stained and easy to distinguish from other particles with both older and newer generation epifluorescence microscopes. Detritus is generally not stained, unlike when the alternative dye YoPro I is used, so this approach may be suitable for sediments. SYBR Green I stained samples need no desalting or heating, can be fixed with formalin prior to filtration, the optimal staining time is 15 min (resulting in a total preparation time of less than 25 min), and counts can be easily performed at sea immediately after sampling. This method may facilitate incorporation of viral research into most aquatic microbiology laboratories. [TOP OF PAGE]

  157. Abundance, morphology and distribution of planktonic virus-like particles in two high-mountain lakes. Pina,S., Creus,A., Ganzález,N., Gironés,R., Felip,M., Sommaruga,R. (1998). J. Plankton. Res. 20:2413-2421. Direct counts of virus-like particles (VLP) by transmission electron microscopy revealed abundances of up to 3 x 107 ml-1 in the plankton of two remote high-mountain lakes in the Alps and in the Pyrenees. Most VLP were icosahedric without tail and with diameters between 40 and 90 nm, but also very large ones with diameter of up to 325 nm were observed. VLP outnumbered bacteria by a factor of 4.2 to 42.8 and bacterial cells were infected with large numbers (>50) of viral particles. This study constitutes the first report on aquatic viruses for alpine lakes and it suggests that they may be an important additional source of bacterial mortality in these systems. [TOP OF PAGE]

  158. Survival and transfer of faecal indicator organisms of wastewater effluents in receiving lake waters. Rajala,R.L., Heinonen-Tanski,H. (1998). Water Sci. Technol. 38:191-194. Water of Lake Kallavesi, which receives wastewater effluents, is used for abstraction of drinking water, for swimming and fishing. It is also used directly for washing and drinking water, both for humans and cattle, especially in summer time. These are the reasons for the present study to follow survival and transfer of faecal indicators downstream from the wastewater treatment plant. Samples were collected in winter and summer from the bottom of the lake at deep sites. At some of the sites the vertical distribution of microbes in summer was also studied. Indicators determined were faecal coliforms, enterococci, sulphite-reducing clostridia and coliphages. The farthest point was 35km for bottom samples. All the indicators could be found in sampling sites near to the discharge point with relatively high numbers. At distant sample sites, coliphages or enterococci were the most abundant. In the winter, coliphages were found up to 18km from the discharge point. In summer, indicators survived well. The results suggest that the direct use of lake water could be considered a health risk. [TOP OF PAGE]

  159. Seasonal abundance in Skagerrak-Kattegat coastal waters and host specificity of viruses infecting the marine photosynthetic flagellate Micromonas pusilla. Sahlsten,E. (1998). Aquat. Microb. Ecol. 16:103-108. Seawater sampled in the Skagerrak and Kattegat coastal waters during the period October 1995 to September 1996 were screened for the occurrence of viruses lytic to marine microalgae. Viruses lytic to the photosynthetic marine picoflagellate Micromonas pusilla (Butcher) Manton & Parke (Prasinophyceae) were detected in all seawater samples screened. Evidence for viral lysis of any other of the 11 algal species tested was not obtained. Several viruses infecting different strains of M. pusilla were isolated. Ten isolated viruses which were tested for host specificity were found to be species specific to M. pusilla and even strain specific to 1-3 of the 6 strains of M pusilla used in the experiment. In the Skagerrak and Kattegat the seasonal abundance of viruses infectious to a M. pusilla strain isolated from the Oslofjord, Norway, was at least 1 order of magnitude higher (average 2.5 x 105 l-1) than viruses infecting 2 M. pusilla strains isolated from Gull of Maine, USA (average 2.2 x 104 and 4.6 x 103 l-1 respectively). [TOP OF PAGE]

  160. The influence of environmental factors on microbiological indicators of coastal water pollution. Serrano,E., Moreno,B., Solaun,M., Aurrekoetxea,J.J., Ibarluzea,J. (1998). Water Sci. Technol. 38:195-199. The relationships between bacteriological and viral indicators of sewage pollution (TC, FC, E coli, FS, Salmonella, somatic coliphages and F-RNA phages) and environmental variables in coastal water and weather were studied at three beaches in San Sebastian, the Basque Country. The microbiological indicators in bathing water presented high counts associated with the following conditions: early morning, overcast skies, low and high tides, groundswell, intense turbidity and the presence of flotsam (P = <0.05). Coliphage density was significantly related (P = <0.05) to cloud cover, groundswell and flotsam. Correlations between microbiological indicators proved high (0.62 less than or equal to or less than or equal to 0.90, P = <0.001). The percentage of Salmonella presented significant (<0.05), albeit low (r < 0.4), correlations with all microbiological parameters. Somatic coliphages also revealed highly significant (0.32 less than or equal to r less than or equal to 0.66) correlations (P = <0.001). Those obtained for F-RNA phages, in contrast, were low (r less than or equal to 0.33). The equations obtained using a multiple regression analysis with a view to predicting microbiological, viral, and Salmonella indicator density demonstrated that environmental variables facilitate the construction of highly significant equations, but that these have low predictive capability (R2 = <0.50). [TOP OF PAGE]

  161. Bacterioplankton dynamics in Lake Constance (Bodensee): Substrate utilization, growth control, and long-term trends. Simon,M., Bunte,C., Schulz,M., Weiss,M., Wuensch,C. (1998). In Baeuerle,E. and Gaedke,U. (eds.), Archiv fuer Hydrobiologie. Spec. issue: Ergebnisse der Limnologie. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart (FRG). The authors studied the dynamics of bacterioplankton growth and the factors controlling it in Lake Constance between 1982 and 1997, but mainly during the last 8 years. In the course of this time, the lake experienced a significant oligotrophication due to an efficient decrease in the phosphorus load. The large changes in nutrient load and concomitant qualitative and quantitative changes in the phytoplankton community made it a particularly interesting time to study bacterial growth dynamics. Both bacterial production (BP) and bacterial numbers (BN) showed persistent annual patterns throughout the period. In most years, highest rates of BP and BN occurred towards the end of the phytoplankton spring bloom. During the clear-water phase, BP and BN varied depending on the grazing pressure by daphnids and decreased towards its end. During summer, BP and BN increased again and to varying extents until the autumnal decline. In 1995 and 1997, highest rates occurred in summer (August, September). In particular, BN remained lower in summer than during the previous part of the season. During the spring bloom, BP was closely correlated either to the biomass of ciliates or of daphnids, but only weakly to chlorophyll, indicating that grazing and thus release of dissolved organic matter by these two herbivores was the most important factor in bottom-up control of bacterial growth at this time. Dissolved free and combined amino acids as well as dissolved free and combined carbohydrates constituted the pool of labile dissolved organic matter to a great extent and were always the major bacterial substrates utilized. At maxima of BP amino acids were preferred whereas carbohydrates were utilized to a greater extent at high and declining bacterial numbers. The bacterial growth efficiency changed seasonally, but in general ranged between 20 and 40 %. During most of the growing season, bacterioplankton growth was co-limited by phosphorus and organic carbon whereas during winter only organic carbon was limiting. Temperature has relatively little direct impact on bacterioplankton growth in the epilimnion because the bacterial assemblages adapted fairly well to the changing ambient temperatures. In the deeper water, temperature directly controlled BP during most of the year. The major loss factors of bacterioplankton comprised phage-induced mortality and grazing by heterotrophic nanoflagellates (HNF), ciliates, and daphnids. On average, phages accounted for 1-24 % of total mortality whereas grazing by HNF for 52-68 %, by ciliates for 14-19 %, and by daphnids for 9-12 %. During the clear-water phase, however, grazing by daphnids dominated by more than 50 %. During oligotrophication, the annual ratio of BP/primary production (PP) integrated from 0 to 20 m varied between 0.09 and 0.29, but without a clear-cut trend. In 1995 and 1996, bacterial growth rates were enhanced and the biomasses of daphnids and autotrophic picoplankton reduced as compared to the previous years. This suggests that grazing control of BP by HNF became more important than before in this late stage of oligotrophication. [TOP OF PAGE]

  162. Morphology and abundance of free and temperate viruses in Lake Superior. Tapper,M.A., Hicks,R.E. (1998). Limnol. Oceanogr. 43:95-103. The morphology and abundance of free viruses were measured in spring, summer, and fall at one site in Lake Superior. Free viral head sizes ranged from 10 to 70 nn and tail length ranged from 10 to 110 nm. The vast majority (98%) of free viral head sizes were less than or equal to 60 nm, smaller than reported in most freshwater habitats. Most of these free viruses (70%) had polyhedral heads and tails, indicative of bacteriophage. Free viral abundance only ranged from 0.1 to 9 x 10(6) viruses ml(-1) in the surface microlayer (top 20 mu m) and subsurface water (20 m) in Lake Superior, but viruses were 2-15 times more abundant in the surface microlayer. This difference may be due to the enrichment of bacterial hosts, higher levels of UV light that induce temperate phage, or differences in viral burst sizes in the surface microlayer relative to subsurface water. Bacterioplankton were always more abundant than free viruses in both the surface microlayer and subsurface water, which resulted in some of the lowest virus-to-bacterium ratios reported for marine or freshwater environments. Temperate viruses from both habitats responded equally to mitomycin-C and UV light treatments used to induce prophage into lytic cycles. An estimated 0.1-7.4% of the bacterioplankton from this site in Lake Superior contained temperate prophage depending on viral burst sizes that were assumed. Three times more bacteria in the surface microlayer may contain temperate viruses compared to bacterioplankton in subsurface waters. In the western arm of Lake Superior, bacterioplankton infected by temperate phage may be more important for the survival of bacteriophage populations than as future carbon sources for new microbial production. [TOP OF PAGE]

  163. Temperate viruses and lysogeny in Lake Superior bacterioplankton. Tapper,M.A., Hicks,R.E. (1998). Limnol. Oceanogr. 43:95-103. The morphology and abundance of free viruses were measured in spring, summer, and fall at one site in Lake Superior. Free viral head sizes ranged from 10 to 70 nm and tail length ranged from 10 to 110 nm. The vast majority (98%) of free viral head sizes were <60 nm, smaller than reported in most freshwater habitats. Most of these free viruses (70%) had polyhedral heads and tails, indicative of bacteriophage. Free viral abundance only ranged from 0.1 to 9 X 106 viruses ml-1 in the surface microlayer (top 20 mum) and subsurface water (20m) in Lake Superior, but viruses were 2-15 times more abundant in the surface microlayer. This difference may be due to the enrichment of bacterial hosts, higher levels of UV light that induce temperate phage, or differences in viral burst sizes in the surface microlayer relative to subsurface water. Bacterioplankton were always more abundant than free viruses in both the surface microlayer and subsurface water, which resulted in some of the lowest virus-to-bacterium ratios reported for marine or freshwater environments. Temperate viruses from both habitats responded equally to mitomycin-C and UV light treatments used to induce prophage into lytic cycles. An estimated 0.1-7.4% of the bacterioplankton from this site in Lake Superior contained temperate prophage depending on viral burst sizes that were assumed. Three times more bacteria in the surface microlayer may contain temperate viruses compared to bacterioplankton in subsurface waters. In the western arm of Lake Superior, bacterioplankton infected by temperate phage may be more important for the survival of bacteriophage populations than as future carbon sources for new microbial production. [TOP OF PAGE]

  164. Size-specific mortality of lake bacterioplankton by natural virus communities. Weinbauer,M.G., Hoefle,M.G. (1998). Aquat. Microb. Ecol. 15 or 156?:103-113. The potential effect that viral lysis has on the cell size distribution of bacterioplankton was investigated during late summer stratification in Lake Plusssee, Germany. Size-specific bacterial mortality due to viral lysis was estimated from in situ samples by a transmission electron microscopy based examination of visibly infected cells (VIC) and in an experiment with varying concentrations of the natural virus community. In all depth layers the highest percentage of cells was found in a cell length class that was smaller for the entire bacterial community (0.3-0.6 mu m) than for VIC (0.6-0.9 mu m). For cells <2.4 mu m the highest frequency of VIC (FVIC) was detected in the size classes 0.6-0.9 and 0.9-1.2 mu m, and the FVIC was high in the size classes 1.2-1.5 (all depth layers) and 1.5-1.8 mu m (meta- and hypolimnion). The estimated mortality due to viral lysis in these size classes was significant with maxima of 29 to 55% in the epilimnion, 30 to 59% in the metalimnion and 56 to 107% in the hypolimnion. In all depth layers the FVIC of bacteria <0.3 mu m in length was ca 30% of that averaged for the entire bacterial community, and in the experiment the percentage of cells <0.3 mu m was highest in enclosures with high viral activity. [TOP OF PAGE]

  165. Significance of viral lysis and flagellate grazing as factors controlling bacterioplankton production in a eutrophic lake. Weinbauer,M.G., Hofle,M.G. (1998). Appl. Environ. Microbiol. 64:431-438. The effects of viral lysis and heterotrophic nanoflagellate (HNF) grazing on bacterial mortality were estimated in a eutrophic lake (Lake Plussee in northern Germany) which was separated by a steep temperature and oxygen gradient into a warm and oxic epilimnion and a cold and anoxic hypolimnion. Two transmission electron microscopy-based methods (whole-cell examination and thin sections) were used to determine the frequency of visibly infected cells, and a model was used to estimate bacterial mortality due to viral lysis. Examination of thin sections also showed that between 20.2 and 29.2% (average, 26.1%) of the bacterial cells were empty (ghosts) and thus could not contribute to viral production. The most important finding was that the mechanism for regulating bacterial production shifted with depth from grazing control in the epilimnion to control due to viral lysis in the hypolimnion. We estimated that in the epilimnion viral lysis accounted on average for 8.4 to 41.8% of the summed mortality (calculated by determining the sum of the mortalities due to lysis and grazing), compared to 51.3 to 91.0% of the summed mortality in the metalimninon and 88.5 to 94.2% of the summed mortality in the hypolimnion. Estimates of summed mortality values indicated that bacterial production was controlled completely or almost completely in the epilimnion (summed mortality, 66.6 to 128.5%) and the hypolimnion (summed mortality, 43.4 to 103.3%), whereas in the metalimnion viral lysis and HNF grazing were not sufficient to control bacterial production (summed mortality, 22.4 to 56.7%). The estimated contribution of organic matter released by viral lysis of cells into the pool of dissolved organic matter (DOM) was low; however, since cell lysis products are very likely labile compared to the bulk DOM, they might stimulate bacterial production. The high mortality of bacterioplankton due to viral lysis in anoxic water indicates that a significant portion of bacterial production in the metalimnion and hypolimnion is cycled in the bacterium-virus-DOM loop. This finding has major implications for the fate and cycling of organic nutrients in lakes. [TOP OF PAGE]

  166. Bacteriophage diversity in the North Sea. Wichels,A., Biel,S.S., Gelderblom,H.R., Brinkhoff,T., Muyzer,G., Schutt,C. (1998). Appl. Environ. Microbiol. 64:4128-4133. In recent years interest in bacteriophages in aquatic environments has increased. Electron microscopy studies have revealed high numbers of phage particles (10(4) to 10(7) particles per ml) in the marine environment. However, the ecological role of these bacteriophages is still unknown, and the role of the phages in the control of bacterioplankton by lysis and the potential for gene transfer are disputed. Even the basic questions of the genetic relationships of the phages and the diversity of phage-host systems in aquatic environments have not been answered. We investigated the diversity of 22 phage-host systems after 85 phages were collected at one station near a German island, Helgoland, located in the North Sea. The relationships among the phages were determined by electron microscopy, DNA-DNA hybridization, and host range studies. On the basis of morphology, 11 phages were assigned to the virus family Myoviridae, 7 phages were assigned to the family Siphoviridae, and 4 phages were assigned to the family Podoviridae. DNA-DNA hybridization confirmed that there was no DNA homology between phages belonging to different families. We found that the 22 marine bacteriophages belonged to 13 different species. The host bacteria were differentiated by morphological and physiological tests and by 16S ribosomal DNA sequencing. All of the bacteria were gram negative, facultatively anaerobic, motile, and coccoid. The 16S rRNA sequences of the bacteria exhibited high levels of similarity (98 to 99%) with the sequences of organisms belonging to the genus Pseudoalteromonas, which belongs to the gamma subdivision of the class Proteobacteria. [TOP OF PAGE]

  167. The role of sunlight in the removal and repair of viruses in the sea. Wilhelm,S.W., Weinbauer,M.G., Suttle,C.A., Jeffrey,W.H. (1998). Limnol. Oceanogr. 43:586-592. We investigated the in situ destruction rates of marine viral particles as well as the decay rates of infectivity for viral isolates along an similar to 400-km transect from oligotrophic offshore waters to productive coastal waters in the Gulf of Mexico. Light-mediated decay rates of viral infectivity averaged over the solar day ranged from 0.7 to 0.85 h super(-1) in surface waters at all stations and decreased with depth in proportion to the attenuation of UVB (305 nm). The destruction rates of viral particles also decreased with depth, although the rates of particle destruction were only 22-61% of infectivity when integrated over the mixed layer. The rates of viral particle destruction indicated that at three of four stations 6-12% of the daily bacterial production would have to be lysed in order to maintain ambient viral concentrations. At the fourth station, where there was a dense bloom of Synechococcus spp. and the mixed layer was shallower, 34-52% of the daily bacterial production would have to be lysed. A comparison of the difference between destruction rates of viral particles and infectivity integrated over the depth of the mixed layer implies that host-mediated repair must have restored infectivity to 39-78% of the sunlight-damaged viruses daily. The calculated frequency of contacts between viral particles and bacterial cells that resulted in infection (contact success) ranged from similar to 18 to 34% in offshore waters, where the frequency of contacts between viruses and bacteria was much lower, to similar to 1.0% at the most inshore station, where contact rates are much higher. This suggests that in offshore waters bacterial communities are less diverse, and that there is less selection to be resistant to viral infection. This paper provides a framework for balancing viral production, destruction, and light-dependent repair in aquatic viral communities. [TOP OF PAGE]

  168. Measurements of DNA damage and photoreactivation imply that most viruses in marine surface waters are inefective. Wilhelm,S.W., Weinbauer,M.G., Suttle,C.A., Pledger,R.J., Mitchell,D.L. (1998). Aquat. Microb. Ecol. 14:215-222. The proportion of viruses in natural marine communities that are potentially infectious was inferred from the relationship between DNA damage and the loss of infectivity in marine viral isolates and measurements of the DNA damage in natural viral communities. Several viral isolates which infect marine Vibrio spp. were exposed to UV-C radiation and the concentration of cyclobutane pyrimidine dimers in the viral DNA was measured with a highly sensitive radioimmunoassay. The loss of infectivity in the UV-exposed isolates was also determined under conditions which either activated or repressed the blue light dependent photolyase enzyme in host cells in order to examine the damage-dependent response of this bacterial repair system. In addition, the accumulation of DNA photodamage during the solar day was measured in DNA isolated from natural viral communities collected along a transect in the western Gulf of Mexico. Using the correlation between DNA damage and infectivity for one of the viral isolates, we estimated the proportion of the natural viral community which was infective. The results imply that, due to light-mediated repair of damaged viral DNA by host-cell mechanisms (photoreactivation), greater than 50% of the viruses in natural communities are infective despite high rates of DNA damage. Furthermore, the accumulation of cyclobutane pyrimidine dimers was highest at the station where the surface mixed layer was shallowest, emphasizing the importance of mixing depth in relation to the accumulation of DNA damage. These experiments demonstrate that physical parameters such as mixing depth are critically interwoven with light penetration in influencing the infectivity of marine viral communities. [TOP OF PAGE]

  169. Population dynamics of phytoplankton and viruses in a phosphate-limited mesocosm and their effect on DMSP and DMS production. Wilson,W.H., Turner,S., Mann,N.H. (1998). Estuarine, Coastal and Shelf Science 46:49-59. The effect of phosphate limitation on viral abundance, phytoplankton bloom dynamics and production of dimethylsulphoniopropionate (DMSP) and dimethyl sulphide (DMS) was investigated in seawater mesocosm enclosures, in a Norwegian fjord, during June 1995. Daily estimates of viral concentrations, based on transmission electron microscope (TEM) counts, varied on an apparently random basis in each of the enclosures. A large Synechococcus spp. bloom developed in an enclosure which was maintained at a high N:P ratio, simulating phosphate-deplete growth conditions. Following phosphate addition to this enclosure, there was a large increase in estimated virus numbers shortly before an apparent collapse of the Synechococcus bloom. It is tentatively suggested that lysogenic viruses were induced following phosphate addition to the phosphate-limited enclosures, and that these observations add to a growing body of evidence which supports the hypothesis that nutrient availability may be responsible for the switch between lysogeny and lytic production. High DMS concentrations and viral numbers were observed on the demise of the flagellate (predominantly Emiliania huxleyi) and diatom blooms, but overall there was no significant correlation. Highest concentrations of DMSP were associated with blooms of E. huxleyi, for which an intracellular concentration of 0.5 pg cell-1 (SD, 0.06) was calculated. Good correlation of DMSP with Synechococcus spp. cell numbers was observed, suggesting that these species of picoplankton may be significant producers of DMSP. No effects of phosphate limitation on DMS and/or DMSP production were evident from the data. [TOP OF PAGE]

  170. Generalized gene transfer by virus-like particles from marine bacteria. Chiura,H.X. (1997). Aquat. Microb. Ecol. 13:75-83. Spontaneous VLP (virus-like particle) production and VLP- mediated gene transfer into Escherichia coli AB1157 as recipient was demonstrated. Five marine isolates (Alc 096, Alc 233, Alc 252, Agrobacterium kieliense and Flavobacterium sp. 11604) were investigated for their potential to produce VLP as well as for the gene transfer capability of these VLPs to the E. coli recipient. These strains are classified as ubiquinone-10- possessing marine bacteria (Q10MB) in the 16s-rRNA Superfamily IV. VLPs were obtained from 100 h cultured broth of all strains examined. VLP-host ratio after 100 h growth culture was: Alc 233, 1.54; Alc 252, 1.26; Alc 096, 1.06; Flavobacterium sp. I1604, 0.69; and A. kieliense, 0.06. These ratios were smaller than those found in the marine environment. However, the spontaneously produced VLP number can be considered as high because the reported numbers are relatively low from coliphage lambda (0.005) and phage Mu ( apprx 0.0001). VLP-mediated gene transfer was examined using an auxotrophic mutant of E. coli (AB1157) with 4 amino acid deficiencies (leu, pro, his, arg) as recipient at multiplicity of infection (MOI) of 0.1. Through this treatment, VLPs showed lethal effect on the recipient. The survival rate of control was: Alc 096, 7%; Alc 252, 8%; A. kise and Flavobacterium sp. 11604) were investigated for their potential to produce VLP as weliense, 17%; Flavobacterium sp, I1604, 31%; and Alc 233,40%. At the same time, all the purified VLPs derived from these 5 strains successfully transferred genes to rescue genetic defects of the recipient. Overall average efficiency of VLP- mediated gene transfer at MOI of 0.1 was estimated to be between 2.62 times 10-3 and 3.58 times 10-5 per VLP particle. Loci of employed genetic markers were dispersed on the E. coli chromosome with mutual distance of 121, 1154, 1397 and 364 kb between them. Since VLPs from different sources showed similar gene transfer efficiency in respect to the genetic marker rescued, it is suggested that VLPs from Q10MB transferred genes as generalized transduction. These results indicate that the VLPs produced by certain marine bacteria may be an important element for both non- specific generalized horizontal gene transfer towards a broad range of bacterial hosts and population control in the marine environment. [TOP OF PAGE]

  171. Release and bioavailability of C, N, P, Se, and Fe following viral lysis of a marine chrysophyte. Gobler,C.J., Hutchins,D.A., Fisher,N.S., Cosper,E.M., Sanudo Wilhelmy,S.A. (1997). Limnol. Oceanogr. 42:1492-1504. [TOP OF PAGE]

  172. The characterisation of Brucella strains isolated from marine mammals. Jahans,K.L., Foster,G., Broughton,E.S. (1997). Vet Microbiol 57:373-382. Small Gram negative coccobacilli isolated from seals, porpoises, dolphins and from an otter road casualty were identified as Brucellae by their colonial and cell morphology, staining characteristics, biochemical activity, agglutination by monospecific antisera and susceptibility to lysis by Brucella specific bacteriophage. Their characterisation, including metabolic profiles, is described. These strains could not be assigned to recognised nomen species of the genus Brucella and it is suggested that they comprise a new nomen species to be called B. maris (sp. nov., type strain 2/94). It is further suggested the nomen species be subdivided into three biovars corresponding to their CO2 requirement, metabolic activity on galactose, dominant antigen and animal host. [TOP OF PAGE]

  173. The abundance of planktonic viruses in antarctic lakes. Kepner,R., Galchenko,V., Wharton,R. (1997). pp. 241-252. In In Lyons,W.B., Howard-Williams,C., and Hawes,I. (eds.), Ecosystem Processes in Antarctic Ice-Free Landscapes. Balkema Press, Rotterdam. [TOP OF PAGE]

  174. Wastewater reclamation at Lake Arrowhead, California: An overview. Madireddi,K., Babcock,R.W.Jr., Levine,B., Huo,T.L., Khan,E., Ye,Q.F., Neethling,J.B., Suffet,I.H., Stenstrom,M.K. (1997). Water Environ. Res. 69:350-362. A demonstration pilot study was conducted in Lake Arrowhead, Calif, to determine the feasibility of reclaiming municipal secondary effluent for indirect potable reuse and stabilizing the lake level during periods of extended drought. The lake, which is the sole drinking water source for the community, was severely affected during the long drought from 1985 to 1991. A 12000-L/d pilot plant was constructed and tested for nearly 3 years. The pilot plant included denitrification followed by alum coagulation/flocculation/sedimentation, sand filtration, primary ozonation, granular activated carbon (GAC) filtration, ultrafiltration (UF)/nanofiltration (NF), reverse osmosis (RO), and final ozone disinfection. A comprehensive analytical testing program was devised to monitor product water quality as well as to compare it with the lake water. Phosphorus and turbidity in the product water were consistently below detection limits (0.02 mg/L and 0.1 nephelometric turbidity unit (NTU), respectively). Product water total organic carbon (TOC) and conductivity levels were 1-2 mg/L and 20-40 mu-Mho/cm, respectively, which were approximately 25%-50% and 30%-50% of the lake concentration. Challenge testing revealed nearly complete removal of pathogenic material (an approximate 21-22 log removal of bacteriophage and 8-10 log removal of Giardia and Cryptosporidium). Trace organic chemical analysis of volatile and base neutral organic compounds indicated that it is possible to produce reclaimed water that is superior to the lake water. Only nitrogen (N) removal did not meet expectations for the entire period. It is anticipated that better process control will ensure meeting the nitrogen product water goals for full scale treatment. [TOP OF PAGE]

  175. Investigations of the marine lysogenic bacterium H24. II. Development of pseudolysogeny in nutrient-rich broth culture. Moebus,K. (1997). Mar. Ecol. Prog. Ser. 148:229-240. Development of pseudolysogeny by 3 strains of H24 was investigated in nutrient-rich liquid cultures. At first, H24(L10), a cured derivative of the lysogenic wild-type strain H24-wt, and the non-virulent mutant vphi-H24-2 of the wild-type phage vphi- H24 residing in H24-wt, were used as a model phage-host system. Attempts to separate phage from pseudolysogenized cells failed due to abundantly present 'cellular PFU'. These release phage particles only after removal of the pseudolysogeny-inducing agent and do so for a period of time. Therefrom it is concluded that phage production in 'cellular PFU' was halted at various stages during the development of pseudolysogeny, depending on time of infection. Observations made with 2 lysogenic H24 strains during the course of several successive cultures are in general agreement with results obtained with the model phage-host system. The nature of the pseudolysogeny-inducing agent remains unknown. Based on information from the literature, the possibility of polysaccharide depolymerase being involved is discussed. [TOP OF PAGE]

  176. Investigations of the marine lysogenic bacterium H24. III. Growth of bacteria and production of phage under nutrient-limited conditions. Moebus,K. (1997). Mar. Ecol. Prog. Ser. 148:241-250. The marine lysogenic bacterium H24, known for the genetic instability of the resident wild-type phage vphi-H24 when propagated in nutrient-rich medium, was investigated by cultivation in synthetic seawater enriched to various levels of yeast extract plus peptone (YEP, in a relation of 1:5). The incidence of phage mutants was found to depend on a balanced equilibrium of nutrient concentration (tested between 0.6 and 600 mg l-1) and the bacterial yield allowed by it on the one hand, and on the duration of incubation and the dilution between successive subcultures on the other. With too-low dilutions used in combination with high nutrient levels, non-virulent mutants, followed by virulent ones, increased in concentration until breakdown of the bacterial population occurred. Conversely, extinction of populations was caused by combinations of low nutrient levels with too-high dilution after too-short incubation periods. At low nutrient levels phage mutants did not influence the outcome of the experiments. However, at nutrient concentrations of 6 and 0.6 mg l-1 release of particles of wild- type phage vphi-H24 was found to be initiated by nutrient addition inducing sufficiently rigorous bacterial multiplication. The latter findings are discussed as an ecologically promising explanation of how phage-host systems are maintained in nature. The number of free virions of vphi-H24, which always remained low, rapidly decreased in the cultures but survived in cell-free filtrates stored in the refrigerator for the same period of time. The loss of virions in cultures is attributed to infection of H24- wt cells which due to their immunity remained unharmed. Pseudolysogenization was indicated at nutrient levels of 600 and 60 mg YEP l-1, but not at lower YEP concentrations. [TOP OF PAGE]

  177. Investigations of the marine lysogenic bacterium H24. I. General description of the phage-host system. Moebus,K. (1997). Mar. Ecol. Prog. Ser. 148:217-228. General features of the marine lysogenic bacterium H24 are described. The bacterial strain was isolated from a sample of North Sea water in 1978. After several consecutive transfers on seawater agar slants spontaneous plaque-formation was observed in 1981. When H24 was grown in bouillon the cultures were found to contain plaque forming units (PFU) at any number between zero and 10-9 ml-1, indicating that spontaneous plaque formation was due to mutational events. Cultures with the highest contents of PFU hardly differed in turbidity from cultures lacking PFU. These observations are ascribed to pseudolysogeny, i.e. immunity of cells against the phage present. When a cured derivative, H24(L10), became available the wild-type phage vphi-H24 residing in H24 was isolated and shown to re-lysogenize H24(L10). It also enabled differentiation between virulent and non-virulent mutants. Mutants of vphi-H24 were found to induce pseudolysogeny. Upon streaking on nutrient agar, material from colonies of pseudolysogenized cells produced various kinds of colonies representing clones of fully sensitive cells, of pseudolysogenized cells, or of mixtures of both. This and accompanying papers report the first intensive studies of a marine lysogenic bacterium. [TOP OF PAGE]

  178. Growth and phage resistance of Anabaena sp. strain PCC 7120 in the presence of cyanophage AN-15. Mole,R., Meredith,D., Adams,D.G. (1997). Journal of Applied Phycology [J. Appl. Phycol. ] 9:339-345. The cyanophage AN-15 was found to have a requirement for either 1 mM calcium or 1 mM magnesium ions to maintain viral stability, whereas 1 mM calcium ions alone were essential for the infection process to proceed in Anabaena sp. strain PCC 7120. Following prolonged incubation, phage-resistant cells were detected at a high frequency (approximately 10 super(-5)) in lysates, as either renewed growth in liquid cultures, or as colonies in confluently lysed lawns. Southern hybridisation failed to detect AN-15 DNA in any of the resistant strains, implying that resistance is unlikely to be due to the presence of temperate phages. A high rate of spontaneous mutation is therefore likely to be the cause of resistance. Two classes of resistant cells were identified; those in which AN-15 failed to attach to host cells, and those in which attachment occurred, but subsequent replication was defective. However, it was possible to overcome phage resistance by the isolation of spontaneous mutants of AN-15, capable of infecting phage-resistant cells. These observations imply that if cyanophages are to be assessed as a means of controlling cyanobacterial blooms in freshwater bodies, the ionic (notably calcium) concentration of the water must be considered, together with the possible need to employ alternative cyanophage strains if resistance to the original one arises. [TOP OF PAGE]

  179. The disinfection of wastewater by ultraviolet light. Moreno,B., Goni,F., Fernandez,O., Martinez,J.A., Astigarraga,M. (1997). Water Sci. Technol. 35:233-235. The aim of this study, carried out over four months at a pilot wastewater treatment facility, was to evaluate ultraviolet treatment of final effluent discharged into bathing waters in coastal zones. Minimum disinfection values were fixed with a target limit of 10-3cfu/100mL for faecal coliforms (FC) in line with the present and proposed European Directive on bathing water quality. Disinfection performance with different sources of water was studied and the disinfectant capacity with other indicator microorganisms was also checked. The target limit was reached using doses around 30mW.s/cm-2. Results of this study suggest that the applied UV dose is influenced by transmittance and the microbiological load. The most sensitive indicators were faecal coliforms, the specific F-RNA bacteriophages being the most resistant. From the results obtained in these experiments, UV treated water is suitable for being discharged into bathing zones, being an alternative to submarine discharges, avoiding high investment and maintenance costs. [TOP OF PAGE]

  180. Isolation of a virus infectious to the harmful bloom causing microalga Heterosigma akashiwo. Nagasaki,K., Yamaguchi,M. (1997). Aquat. Microb. Ecol. 13:135-140. A virus infecting the harmful bloom causing microalga Heterosigma akashiwo (Raphidophyceae) was isolated from the coastal water of Nomi Bay, Japan, in July 1996. The isolate caused lysis in 2 strains of H. akashiwo tested and numerous virus-like particles (VLPs) appeared in the lysed algal culture, whereas virus multiplication was not detected in the healthy culture of H. akashiwo without its inoculation. Thus, fulfilling Koch's postulate, it was considered to be a virus and designated HaV(Heterosigma akashiwo virus) clone GSNOU-30. The virus particle is icosahedral, lacking a tail, and 202 ± 6 nm (average ± standard deviation) in diameter with an electron-dense roundish core that is distinct from the capsid. The virus stained positive with DAPI, indicating that it possesses a double stranded DNA genome. The virus proliferated in the protoplasm of the host cell as had previously been observed in H. akashiwo cells from a natural red tide population. The virus did not cause lysis of Chattonella antiqua, C. verruculosa or Fibrocapsa japonica (Raphidophyceae) as well as 15 strains of phytoplankton belonging to other classes. It is most noteworthy that 3 strains of H. akashiwo isolated from Hiroshima Bay, Japan, were resistant to GSNOU-30, suggesting that the viral infectivity is not species-specific but strain-specific. These results suggest that the virusis involved in the population dynamics of H. akashiwo, playing a role as a selector to increase genetic diversity of a host species. [TOP OF PAGE]

  181. Evidence for groundwater and surface marine water contamination by waste disposal wells in the Florida Keys. Paul,J.H., Rose,J.B., Jiang,S.C., Xhou,X., Cochran,P., Kellogg,C., Kang,J.B., Griffin,D., Farrah,S., Lukasik,J. (1997). Water Res. 31:1448-1454. [TOP OF PAGE]

  182. Coliphage and indigenous phage in Mamala Bay, Oahu, Hawaii. Paul,J.H., Rose,J.B., Jiang,S.C., London,P., Xhou,X., Kellogg,C. (1997). Appl. Environ. Microbiol. 63:133-138. Public concern over the discharge of primarily treated sewage by two offshore outfalls in Mamala Bay, Oahu, prompted a multidisciplinary study to determine the impact of such activities on the water quality in the bay and at adjacent recreational beaches. As part of this study, we determined the abundance of coliphage as an indicator of fecal pollution along with total viral direct counts and phages infective for Vibrio parahaemoltyicus 16 at stations in Mamala Bay in four quarterly samplings over 13 months. Coliphage ( lt 1 to 1.2 times 10-3/liter) were found during each quarterly sampling along an offshore transect to the Sand Island waste treatment facility outfall. The nonpoint coastal stations (Pearl Harbor, Ala Wai Canal, and Ke'ehi Lagoon) had high levels of coliphage during the storm event sampling in February 1994 but much lower levels or none when sampled during dry weather. Coliphage were absent at all samplings at Waikiki Beach and at the control station off Diamond Head. Viral direct counts in eutrophic coastal stations (Pearl Harbor, Ke'ehi Lagoon, Ala Moana Beach, and Ala Wai canal) averaged 10-9/liter, while counts at offshore stations ranged from 9 times 10-7 to 1 times 10-9 viruses/liter, values similar to those for other marine environments. Vibriophage were found mainly in eutrophic coastal environments (Ala Wai Canal, Pearl Harbor, and Ke'ehi Lagoon) and at the Sand Island Transect stations D1 and D2. The greatest abundance was found during the storm event (February 1994) sampling. These results suggest that the Sand Island outfall influenced the water quality of the immediate surrounding waters but had little effect on the quality of the recreational beaches. Nonpoint discharge sources appeared to be more important in the distribution of fecal indicators in the coastal zone. [TOP OF PAGE]

  183. Mycobacteriophage specific for the Mycobacterium tuberculosis complex. Pearson,R.E., Dickson,J.A., Hamilton,P.T., Little,M.C., Beyer,Jr.W.F. (1997). Becton, Dickinson and Company. 402066(5,612,182). Franklin Lakes, NJ. Mycobacteriophage DS6A has been characterized and found to specifically infect all species of the TB complex, without any detectable infection of mycobacteria species other than those of the TB complex. DNA sequence analysis revealed several potential open reading frames, including one encoding a protein analogous to gp37 of mycobacteriophage L5 and a second encoding a protein with significant homology to the S. coelicolor DNA polymerase b subunit. Based on the DNA sequence analysis, cloning sites can be identified for insertion of reporter genes, making DS6A useful as a reporter phage for specific detection and identification of species of the TB complex. [TOP OF PAGE]

  184. Advances in the study of marine viruses. Proctor,L.M., Lita,M. (1997). Microscopy Research and Technique 37:136-161. Free viruses are abundant in the world's oceans. With this realization has come renewed interest in marine viruses and the role viruses play in structuring marine planktonic communities, primarily members of the microbial assemblage. The principal means of studying marine viruses has been by electron microscopy. This review discusses the use of microscopy to study free viruses and compares the ultrastructure of free viruses with bacteriophages and viruses which have been cultured from marine hosts. ¶ Many of the free viruses are smaller than typical cultured bacteriophages, which suggests that either many native phages are smaller than cultured phages or that many of the free viruses may be members of those phage families with smaller size classes or, in some cases, that many free viruses may be eukaryotic viruses. Some of the forms currently considered free viruses may be “defective phage” or “phage ghosts,” noninfectious particles produced by bacteria, or virus-sized inorganic/organic colloids and warrant further study. ¶ Gross virus ultrastructure cannot be used as the sole criterion for determining marine virus diversity, since, as with many microbes, many unrelated viruses have similar morphological characters. Determination of DNA or RNA content as well as studies of protein and DNA relatedness of marine viruses will be needed if we are to understand the complexity of marine virus assemblages. Another important direction for future work is the need for marine bacteriophage/host and virus/host systems in order to study the biology of virus infection. Microsc. Res. Tech. 37:136–161, 1997. [TOP OF PAGE]

  185. Comparison of PCR and plaque assay for detection and enumeration of coliphage in polluted marine waters. Rose,J.B., Zhou,X., Griffin,D.W., Paul,J.H. (1997). Appl. Environ. Microbiol. 63:4564-4566. A total of 68 marine samples from various sites impacted by sewage and storm waters were analyzed by both the plaque assay and a reverse transcriptase (RT) PCR technique for F1-specific coliphage. The coliphage levels detected by the plaque assay averaged 1.90 3 104 PFU/100.0 ml. Using a most probable number (MPN) PCR approach, the levels averaged 2.40 3 106 MPN-PCR units/100.0 ml. Two samples were positive by RT-PCR but negative by plaque assay, and 12 samples were positive by plaque assay but negative by RT-PCR (levels lower than 11.00 PFU/100.0 ml). The host system used for the plaque assay may detect somatic coliphage in addition to the F1-specific coliphage. When it is used as an indicator of pollution, contamination may be missed with more restrictive systems. The difference in results may be due to the sensitivity, specificity, or inhibition of RT-PCR in marine samples. This study provides information on quantifying PCR results by an MPN method and insights into interpretation of PCR data for detection of viruses in marine environments. [TOP OF PAGE]

  186. Adsorption of viruses in water environment onto solid surfaces. Sakoda,A., Sakai,Y., Hayakawa,K., Suzuki,M. (1997). Water Sci. Technol. 35:107-114. Recently the contamination of water environment involving rivers, lakes, the sources of drinking water, etc. by viruses has been paid attention to as a new threat. The behavior of the viruses found in water environment is not well understood so far. However, it is suspected in general that the viruses are adsorbed onto solid surfaces such as suspended solids and sediment and keep their activities for a long time. Most likely, it is true that the adsorption of the viruses onto solid surfaces is one of the major factors controlling their transport and survival in water environment. In this work, the adsorption equilibrium relations of model viruses in water environment and their activities on solid surfaces were investigated. The Escherichia coli phage such as Q beta , fr, MS2 and T4 were employed for experiments as model viruses, and cellulose and its derivatives, kaolin, carbon black, etc. were chosen as model solid surfaces. All the adsorption isotherms of model viruses on model surfaces were successfully written as the linear expression by the Henry equation in the concentration range of 10 super(2)-10 super(7) [PFU/ml]. The resultant Henry constants were correlated with the total acidity of the solid surfaces. Stability of the model viruses was completely different when they were adsorbed on the solid surfaces and when they were suspended in water. The viruses adsorbed on the solid surfaces were significantly stable compared with the suspended ones regardless of the surface properties. It is suggested that the shrinkage of the virus is one of the important survival factors and the adsorption onto solid surfaces enhances their activities. [TOP OF PAGE]

  187. Characterization of host-range mutants of cyanophage N-1. Sarma,T.A., Kaur,B. (1997). Acta Virol. 41:245-250. Fifteen host-range (h) mutants of cyanophage N-1 were characterized with reference to their efficiency of plating, time of appearance, morphology and size of plaques on Nostoc muscorum and its three phage-resistant (Nm 1/N-1, Nm 2/N-1 and Nm 8/N-1) mutants. While phage N-1 did not adsorb to the three phage-resistant mutants, the h mutants differed one from the other in having lower or higher adsorption rate constants on N. muscorum or the phage-resistant mutants. The inability of majority of h mutants isolated on Nm 1/N-1 to grow in Nm 8/N-1 was shown to be due to a failure of adsorption. The h mutants also differed one from the other in their reversion (back mutation) frequencies. The lethal doses (LD sub(37)) required to kill 37% of free phage particles after UV-irradiation, heating and ethylenediamine tetraacetate (EDTA) treatment greatly varied. Most of the h mutants were found to be considerably more sensitive to UV and thermic inactivation than N-1 while they were resistant to EDTA. The h mutants except five of them were unable to multiply at 40 degree C. The significance of these features is discussed. [TOP OF PAGE]

  188. Formation of submicron colloidal particles from marine bacteria by viral infection. Shibata,A., Kogure,K., Koike,I., Ohwada,K. (1997). Mar. Ecol. Prog. Ser. 155 (not 154):303-307. We tested the hypothesis that viral lytic infection leads to the formation of submicron-sized colloidal particles originating from marine bacteria. Laboratory experiments were performed using a marine bacterium, Vibrio alginolyticus, and its infectious phage. A particle counter was used to determine abundance and size distribution of particles. We found that the non-living submicron sized particles (size range from 0.38 to 0.7 mum in diameter) increased rapidly along with a decrease of bacteria and an increase of phage, indicating that these particles are cell debris originating from bacteria. These particles were stained faintly by acridine orange but were not countable due to the amorphous shape. These results show that amorphous submicron particles are produced by viral lysis of bacteria. This process may be one of the major pathways of colloid formation associated with microbial food webs in the sea. [TOP OF PAGE]

  189. Viruses in aquatic ecosystems. A review. Sime-Ngando,T. (1997). Annee Biologique 36:181-210. Even though the contribution of water ecosystems for disseminating enteric viral pathogens has been known for decades, the importance of wild virions iii structuring aquatic communities and food webs has only come to light relatively recently. Evidences of viral infections in both pro-and eukaryotic phytoplankton, as well as in heterotrophic bacterio-and protozooplankton, have recently brought marine biologists to question the impact of viroplankton on processes such as (1) the mortality of microorganisms, (2) the nutrition of heterotrophic protists, (3) the promotion of genetic material exchanges among microbial populations, (4) the maintenance of species diversity, (5) the induction of planktonic aggregates, and (6) the cycling of organic matter in aquatic ecosystems. In this paper, all these points are reviewed and discussed, in the light of recent contributions to the ecology of aquatic viruses, for evidence of the impact of viruses on both steady and non-steady state processes in fresh- and salt-waters.

    Viruses are ubiquitous, abundant and dynamic components of pelagic ecosystems. They are, undoubtedly, more diversified than the phage -like morphotypes that are generally characterized by the presence of an icosa- or octahedral head and a tail, via observations under electron microscope. The diversity of planktonic viruses is further enhanced from the genetic viewpoint, and likely implies the diversity of sensible hosts. Genetically related marine phages are likely widely distributed in the space (i. e. without significant geographical segregation), suggesting prevalence of a reduced competition among viral ''populations'', and that the main biotic limiting factor for a viral ''species'' production is the density of the sensible host. Some viral ''species'', known from marine systems, typically harbor knob-like projections and long spines (i. e. previously not noted from non.-aquatic habitats), which are suggested to increase the efficiency of hitting a specific host, especially in oligotrophic waters. Despite the general scarcity of viral isolates that lyse ciliated protozooplankton and metazoan zooplankton, it is becoming increasingly evident that most of the pelagic pro-and eukaryotic organisms are subject to infectious attacks from ambient ''free-living'' viruses.

    Quantitatively, recent total counts from the plankton generally fall in between 10(4) and 10(8) viruses ml(-1), with seasonal high densities in spring and summer, and a lowering tendency in abundance from the coastal to the open marine systems, and from the surface to the depth waters, likely in relation to temperature and the organic matter load. it was recently shown that lytic infection, rather than induction of lysogeny, is responsible for the majority of bacteriophage production in the plankton, especially in the coastal marine and surface waters and during blooming events, where the threshold-product level of virus x bacteria numbers of greater than or equal to 10(12) for the start of a viral-lytic activity is generally achieved. Closed linear relationships have been reported between viroplankton dynamics and bacteria, algae and nutrients. Because of the preponderance of allochtonous organic matter and cyanobacterial cells in lakes as compared to oceanic systems, the virus-to-bacteria ratio in lakes are significantly higher than in marines systems, although there is little trend in the virus-to-bacteria ratio with increasing trophy, and despite the occurrence of more bacteria per unit chlorophyll in lake samples.

    The functional impact of virions on the structure and metabolism of planktonic communities is more important than their quantitative importance, as viruses represent only a minor fraction of the total planktonic biomass. The viral-induced mortality of microbial communities in marine systems is estimated to represent about 30 and < 10 pour 100 of the mortality of bacterio- and phytoplankton, respectively. Based on one study, the contribution of viruses to bacterial mortality in lakes seems considerably lower than in marine systems. The greatest impact of viruses on aquatic communities is likely through hazardous (i.e. non-steady state) processes which are difficult to quantified, such as the promotion of genetic material exchanges among populations and the maintenance of species diversity. The lytic pressure from virulent viruses may act as a ''nonstop'' inductor of modifications in the genetic heritage of host-organisms, thereby increasing the potential of these hosts to share their habitat with homologous species, i.e. with similar nutritional requirements.

    It has recently been shown that lysates resulting from phage infection can caused a significant increase in metabolic activity of noninfected bacterioplankton community, but the growth efficiency of these noninfected hosts decreased in the presence of viruses, likely because of the increase in bacterial energy demand associated with extracellular degradation of polymers that are prevalent in viral lysates. This seems to verify the hypothesis on a substantial contribution of the lytic activity from viruses, to the cycling of organic matter in aquatic systems. Viral lytic production may indeed (1) reduce the bacterial biomass contribution to the transfer of metabolic energy on to higher-order consumers, (2) result in an increase of bacterial secondary production in the absence of an increase in the ambient primary production, and (3) increase competition between bacterial exo- or ectoenzyme activity and the feeding activity of protozoa on high molecular weight polymers (including viruses), although ingestion of viruses by protists seems to be of less importance in the carbon flows through the microbial food web in pelagic systems.

    However, almost all studies on the ecology of pelagic viruses are done during a limited period of year, mainly in marine waters situated in temperate zones. The data discussed in this paper are thus to be considered as preliminary data. Nevertheless, viruses undoubtedly influence to various degrees the biological processes in aquatic ecosystems. The quantitative assessment of their functional impact is thus required for incorporation into models that simulate flues of matter, nutrients and energy in aquatic systems. This task is to be include on the agenda of both marine and freshwater biologists, as a high priority concern for the near future. [TOP OF PAGE]

  190. Induction of a temperate marine cyanophage by heavy metal. Sode,K., Oonari,R., Oozeki,M. (1997). J. Mar. Biotechnol. 5:178-180. The activity of a temperate marine cyanophage, ms-1, of Synechococcus sp. NKBG 042902, was induced by Cu2+. This induction was specific to Cu2+ and dependent upon Cu2+ concentration. Cr, Pb, Co, and Zn were not effective as inducers. These results suggested that Cu2+ is a significant inducer for lysogenic cyanobacterial cells and consequently will be a potential trigger for changes in the cyanobacterial population in the marine environment. [TOP OF PAGE]

  191. Theoretical models for control of bacterial growth rate, abundance, diversity and carbon demand. Thingstad,T.F., Lignell,R. (1997). Aquat. Microb. Ecol. 13:19-27. Our conceptual understanding of the role of heterotrophic bacteria in pelagic ecosystems and in ocean biogeochemical cycles is closely Linked to our understanding of how their growth rate, abundance, and diversity is controlled. Here we discuss consequences of the simplifying assumption that there are only 5 potentially important interactions between heterotrophic bacteria and their biological and chemical environment. We consider 3 possible types of growth rate limitation: (1) organic carbon, (2) inorganic phosphate, and (3) organic and inorganic nitrogen; and 2 types of cell losses: (1) predation by heterotrophic flagellates, or (2) lysis by infectious viruses. Incorporating this into simple food web structures, we discuss 4 classes of models, 2 based on carbon limitation and 2 based on mineral nutrient limitation of bacterial growth rate. Bacterial abundance is assumed to be controlled by protozoan predation in all cases. For each class, we derive expressions describing bacterial carbon demand, and discuss the control of bacterial carbon demand, growth rate and diversity. It is shown how models predicting an ecosystem production of dissolved organic carbon (DOG) exceeding bacterial carbon demand may be constructed assuming either a low degradability of the DOG, or mineral nutrient limitation of bacterial growth rate. For 2 classes of models, infectious viruses are shown to affect neither growth rate nor abundance of the steady state bacterial community. For all 4 classes of models, viruses are suggested to control diversity of the steady state bacterial community. [TOP OF PAGE]

  192. Accumulation of degradable DOC in surface waters: Is it caused by a malfunctioning microbial loop? Thingstad,T.F., Hagstrom,A., Rassoulzadegan,F. (1997). Limnol. Oceanogr. 42:398-404. Recent literature indicates that dissolved organic carbon (DOC) may accumulate in productive surface waters. Such accumulation will allow export of DOC to the aphotic zone by diffusion and downwelling. As an alternative to models based on low degradability, we here propose a mechanism where bacterial carbon consumption is restricted due to food web mechanisms controlling both growth and biomass of the bacteria: growth rate is kept low by bacteria-phytoplankton competition for mineral nutrients, and biomass is kept low by bacterial predators. With such a mechanism, otherwise degradable material may accumulate and become subject both to chemical transformation and vertical transport. The steady-states of a model describing the interactions between heterotrophic bacteria, phytoplankton, and bacterivorous protozoa is used to explore how the balance between DOC production and consumption shifts along a gradient from oligotrophy to eutrophy. [TOP OF PAGE]

  193. Bacterial population dynamics in a meromictic lake. Tuomi,P., Torsvik,T., Heldal,M., Bratbak,G. (1997). Appl. Environ. Microbiol. 63:2181-2188. Polyclonal antibodies against nine different bacteria isolated from Lake Saelenvannet in western Norway were produced, and the population dynamics of these strains in the lake were monitored through two spring seasons by immunofluorescence staining. The total counts of bacteria varied over time and space from 1.5 times 10-6 to 1.5 times 10-3 cells ml-1. The counts of specific bacteria were in the range of 10-3 to 10-4 cells ml-1 or less; in sum, they generally made up less than 1% of the bacterial community. Some populations showed significant changes in abundance, with blooms lasting 1 to 3 weeks. The rate of change (increase and decrease) in abundance during blooms was estimated to be 0.2 to 0.6 day-1. The average virus-to-bacteria ratio was 50, and there was a significant correlation between the abundances of virus and bacteria. Both protozoan grazing and lytic virus infection were assessed as possible mechanisms driving the variations in bacterial population density. [TOP OF PAGE]

  194. Photoreactivation compensates for UV damage and restores infectivity to natural marine virus communities. Weinbauer,M.G., Wilehelm,S.W., Suttle,C.A., Garza,D.R. (1997). Appl. Environ. Microbiol. 63:2200-2205. We investigated the potential for photoreactivation to restore infectivity to sunlight-damaged natural viral communities in offshore (chlorophyll a, lt 0.1 mu-g liter-1), coastal (chlorophyll a, ca. 0.2 mu-g liter-1), and estuarine (chlorophyll a, ca. 1 to 5 mu-g liter-1) waters of the Gulf of Mexico. In 67% of samples, the light-dependent repair mechanisms of the bacterium Vibrio natriegens restored infectivity to natural viral communities which could not be repaired by light-independent mechanisms. Similarly, exposure of sunlight-damaged natural viral communities to gt 312-nm-wavelength sunlight in the presence of the natural bacterial communities restored infectivity to 21 to 26% of sunlight-damaged viruses in oceanic waters and 41 to 52% of the damaged viruses in coastal and estuarine waters. Wavelengths between 370 and 550 nm were responsible for restoring infectivity to the damaged viruses. These results indicate that light-dependent repair, probably photoreactivation, compensated for a large fraction of sunlight-induced DNA damage in natural viral communities and is potentially essential for the maintenance of high concentrations of viruses in surface waters. [TOP OF PAGE]

  195. Comparison of epifluorescence and transmission electron microscopy for counting viruses in natural marine waters. Weinbauer,M.G., Suttle,C.A. (1997). Aquat. Microb. Ecol. 13:225-232. Transmission electron microscopy (TEM) and epifluorescence microscopy of DAPI and Yo-Pro-1 stained samples were used to estimate viral abundance in natural communities along a transect from the oligotrophic central Gulf of Mexico to the productive near-shore waters at Post Aransas, Texas (USA). Estimates of viral abundance based on TEM averaged only 66% (range 26 to 108%) of those made using epifluorescence microscopy and the cyanine-based dye, Yo-Pro-1. DAPI staining provided estimates that were much closer and averaged 86% (range 72 to 109%) of those made using Yo-Pro. However, all 3 methods provided similar estimates at viral abundances <10(6) ml(-1). The precision of the Yo-Pro and DAPI methods (coefficient of variation 8 and 11%, respectively) was much greater than for the TEM method (25%). Experiments with cultures indicated that grazing by flagellates was unlikely to be a significant source of viral-size particles that could interfere with the DAPI or Yo-Pro method. Estimates of viral abundance made using the Yo-Pro method ranged from 0.3 x 106 to 39 x 106 ml(-1) in surface water along the transect. Across the investigated environments viral and bacterial abundances were well correlated (r = 0.929), although the slope of the relationship was significantly greater than 1, indicating that viral abundance increased more rapidly than that of bacteria. These results extend previous observations by showing that epifluorescence microscopy is suitable for counting viruses in very oligotrophic waters, that DAPI and Yo-Pro stained samples provide similar estimates of viral abundance and that grazing by flagellates is not a significant source of particles that could interfere with the epifluorescence method. The study supports the use of epifluorescence microscopy over TEM for obtaining accurate estimates of viral abundances in natural waters. [TOP OF PAGE]

  196. Lysogenic and lytic viral production in marine microbial communities. Wilson,W.H., Mann,N.H. (1997). Aquat. Microb. Ecol. 13:95-100. It is now well established that viruses are an abundant component of marine ecosystems and they are being increasingly recognised and accepted as important contributors to element cycling within the microbial loop. However, some of the key questions regarding the ecological significance of viruses in the marine environment still remain largely unanswered. Thus, particular interest is currently focused on the extent to which lytic production or lysogeny predominates and the nature of factors in the marine environment, particularly nutrient availability and multiplicity of infection (MOI), which might influence the lysis/lysogeny 'decision'. The present evidence is still insufficient to unambiguously assess the relative ecological significance of lysogeny versus lysis and progress in this area will rely on the development and application of new techniques. This review attempts to collect recent information relating to this central question, focusing particularly on those viruses which infect the bacterioplankton and nano- and picophytoplankton. [TOP OF PAGE]

  197. Virus a la sauce Yo-Pro: microwave-enhanced staining for counting viruses by epifluorescence microscopy. Xenopoulos,M.A., Bird,D.F. (1997). Limnol. Oceanogr. 42:1648-1650. A recently developed method for enumerating aquatic viruses (Yo-Pro stained) was modified to reduce staining time and allow counting of fixed samples. Marine and freshwater virus samples to be enumerated were stained with the cyanine-based dye Yo-Pro-1 by using microwave irradiation, which reduced incubation time from 48 h to 4 min. The modified method and the original protocol yielded similar viral estimates. Easier sample handling and the addition of fixed sample capability should allow epifluorescence counting of viruses to become a routine part of field studies of viral ecology. [TOP OF PAGE]

  198. Microwave enhanced staining for counting viruses by epifluorescence microscopy. Xenopoulos,M.A., Bird,D.F. (1997). Limnol. Oceanogr. 42:1648-1650. [TOP OF PAGE]

  199. Lipopolysaccharide dependence of cyanophage sensitivity and aerobic nitrogen fixation in Anabaena sp. strain PCC 7120. Xu,X., Khudyakov,I., Wolk,C.P. (1997). Journal of Bacteriology [J. BACTERIOL. ] 179:2884-2891. Fox super(-) mutants of Anabaena sp. strain PCC 7120 are unable to fix dinitrogen in the presence of oxygen. A fragment of the DNA of Anabaena sp. was cloned by complementation of a spontaneous Fox super(-), cyanophage-resistant mutant, R56, and characterized. Random insertion of transposon Tn5 delimited the complementing DNA to a 0.6-kb portion of the cloned fragment. Sequencing of this region and flanking DNA showed one complete open reading frame (ORF) similar to the gene rfbP (undecaprenyl-phosphate galactosephosphotransferase) and two partial ORFs similar to genes rfbD (GDP-D-mannose dehydratase) and rfbZ (first mannosyl transferase), all of which are active in the synthesis of the O antigen unit of the lipopolysaccharide (LPS) component of the outer membrane of gram-negative bacteria. In a transposon (Tn5-1087b)-induced, Fox super(-), cyanophage-resistant mutant, B14, the transposon was found within the same rfbP-like ORF. The three ORFs were insertionally inactivated with the omega cassette or with Tn5::omega. Only the insertions in the rfbZ- and rfbP-like ORFs led to resistance to cyanophages A-1(L) and A-4(L) and to a Fox super(-) phenotype. Electrophoretic analysis showed that interruption of the rfbZ- and rfbP-like ORFs resulted in a change in or loss of the characteristic pattern of the lengths of the LPS, whereas interruption of the rfbD-like ORF merely changed the distribution of the lengths of the LPS to one with a greater prevalence of low molecular weights. According to electron microscopy, interruption of the rfbP-like ORF may have led to aberrant deposition of the layers of the heterocyst envelope, resulting in increased leakage of oxygen into the heterocyst. The results suggest that modified LPS may prevent cyanophage infection of Anabaena sp. vegetative cells and the formation of a functional heterocyst envelope. [TOP OF PAGE]

  200. Parasitic action of marine bdellovibrios on prawn-pathogenic bacteria and other bacteria. Yang,S., Huang,Q. (1997). Journal of Xiamen University. Natural science/Xiamen Daxue Xuebao. Xiamen [J. Xiamen Univ. [Nat. Sci. ]/Xiamen Daxue Xuebao] 36:449-453. Parasitic action of marine bdellovibrios on 25 strains of prawn-pathogenic bacteria E. coli, B. subtilis, Pseudomonas aeruginosa, and Staphylococcus aureus were determined by selection technique of double agar plates containing host. The results showed that the bdellovibrio strains tested had different host range, and that all the bacterial strains tested for host capability were capable of being host cells for some bdellovibrio strains, forming obvious plaques in the double agar plates. Morphology and phage process of bdellovibrios were investigated by phase contract microscopy and electron microscopy. [TOP OF PAGE]

  201. Study of viral and bacterial indicators in cockles and mussels. Beril,C., Crance,J.M., Leguyader,F., Apaire-Marchais,V., Leveque,F., Albert,M., Goraguer,M.A., Schwartzbrod,L., Billaudel,S. (1996). Marine Pollution Bulletin 32:404-409. Forty-two mussel and cockle samples were collected from two polluted areas of the Atlantic coast in France. No cytopathogenic enterovirus was isolated after inoculation to cell cultures, but enterovirus RNA was detected from 100% of the mussels and 80% of the cockle samples. Gene probes did not detect any HAV RNA but it was detected by PCR in 33% of cockle and 43% of mussel extracts. Infectious HAV could be isolated by inoculation to PLC/PRF/5 cells from five of six HAV-PCR positive samples. Viral indicators represented by somatic coliphages were present in 100% of the cockle and 86% of the mussel samples. Regarding bacterial indicators, 100% of the mussel and 95% of the cockle samples contained less than 300 faecal coliforms/100 g. No correlation could be established between the concentrations of faecal coliforms and streptococci, nor between the presence of somatic coliphages and the presence of virus or viral RNA. [TOP OF PAGE]

  202. Virus-like particles in a summer bloom of Emiliania huxleyi in the North Sea. Brussaard,C.P.D., Kempers,R.S., Kop,A.J., Riegman,R., Heldal,M. (1996). Aquat. Microb. Ecol. 10:105-113. The importance of viruses in controlling a bloom of the coccolithophorid Emiliania huxleyi in the North Sea was investigated during summer 1993. Viral infection of E. huxleyi was highest in the decaying phase of the bloom. Up to 50% of E. huxleyi cells were visibly infected. For E. huxleyi, 2 types of virus-like particles are reported. They differed in size and were occassionally found within the same cell. The infection level of the large virus-like particles was never higher than 25%. Viral lysis of E. huxleyi within the nitrogen-limited decaying phase of the bloom seemed an important source of organic carbon utilized by bacteria. In addition to infection in E. huxleyi, we also found severe viral infection in Chrysochromulina sp. Our results show that in natural ecosystems viruses can be a significant source of phytoplankton mortality, influencing phytoplankton (bloom) dynamics and the microbial food web. [TOP OF PAGE]

  203. Genetic diversity in marine algal virus communities as revealed by sequence analysis of DNA polymerase genes. Chen,F., Suttle,C.A., Short,S.M. (1996). Appl. Environ. Microbiol. 62:2869-2874. Algal-virus-specific PCR primers were used to amplify DNA polymerase gene (pol) fragments (683 to 689 bp) from the virus-sized fraction (0.02 to 0.2 mu m) concentrated from inshore and offshore water samples collected from the Gulf of Mexico. Algal-virus-like DNA pol genes were detected in five samples collected from the surface and deep chlorophyll maximum. PCR products from an offshore station were cloned, and the genetic diversity of 33 fragments was examined by restriction fragment length polymorphism and sequence analysis. The five different genotypes or operational taxonomic units (OTUs) that were identified on the basis of restriction fragment length polymorphism banding patterns were present in different relative abundances (9 to 34%). One clone from each OTU was sequenced, and phylogenetic analysis showed that all of the OTUs fell within the family Phycodnaviridae. Four of the OTUs fell within a group of viruses (MpV) which infect the photosynthetic picoplankter Micromonas pusilla. The genetic diversity among these genotypes was as large as that previously found for MpV isolates from different oceans. The remaining genotype formed its own clade between viruses which infect M. pusilla and Chrysochromulina brevifilum. These results imply that marine Virus communities contain a diverse assemblage of MpV-like viruses, as well as other unknown members of the Phycodnaviridae. [TOP OF PAGE]

  204. The diversity of bacteria, eukaryotic cells and viruses in an oligotrophic lake. Corpe,W.A., Jensen,T.E. (1996). Applied Microbiology and Biotechnology 46:622-630. An in situ transmission electron microscopic study of biomass samples concentrated from oligotrophic lake water revealed a variety of virus-infected microbial cells and many free viruses and virus-like particles. The most abundant group of microorganisms in screened and filtered water-column samples were 2 mu-m or less in diameter, and included representatives of several oligotrophic genera, Prosthecomicrobium, Ancyclobacter, Caulobacter and Hyphomicrobium. Among the prokaryotic host cells, which included both heterotrophs and autotrophs, on the basis of electron microscope observations. approximately 17% were infected with bacteriophage or bore adherent phage particles on their surfaces. Several bacterial morphotypes were observed among the prokaryotic hosts. Water samples passed through a 20-mu-m Nitex screen allowed us to concentrate and examine the larger host cells as well, including several species of single-celled algae and two amoeba species. The infected algal cells included those Chlorella-like in appearance, photosynthetic flagellates and others that could not be positively identified. About one-third of the eukaryotic cells were infected by viruses that were larger (150-200 nm) and structurally more complex than bacteriophages (50-60 nm). None of the viruses have been isolated, but when 0.2 mu-m filtrate from a biomass sample was spotted onto lawns of four representative heterotrophs and a Chlorella, the clearing observed was taken as evidence of lysis. Cyanobacterial lawns showed no plaques. Thin sections of two amoeba showed food vacuoles containing what appeared to be virus particles of a type seen in certain prokaryotic and eukaryotic cells in the biomass. [TOP OF PAGE]

  205. A method for the enumeration of Aeromonas bacteriophage in aquatic environments. Flint,K.P. (1996). Lett. Appl. Microbiol. 22:244-248. Bacteriophage were isolated against type strains and environmental isolates of Aeromonas hydrophila, Aeromonas sobria and Aeromonas caviae. A most probable number method for estimating the number of bacteriophage in a water sample was devised and tested using some of these isolates. The maximum number of bacteriophage against all three type strains were found in water from below a sewage effluent outfall. This corresponds to the increased numbers of each species of bacterium also found in this water sample. High numbers of bacteriophage against Aer. hydrophila were also found in the lake sample examined. Bacteriophage against Aer. caviae were rare in water samples other than those contaminated with sewage effluent. [TOP OF PAGE]

  206. In situ production and decay of marine viruses. Garza,D.R. (1996). University of Texas at Austin. [TOP OF PAGE]

  207. Biological effectiveness of environmental radiation in aquatic systems, measurements by T7-phage sensor. Gaspar,S., Berces,A., Ronto,G., Grof,P. (1996). J. Photochem. Photobiol. B Biol. 32:183-187. Bacteriophage T7 as a biologic sensor was used for systematic underwater UV measurements at the freshwater lake Gyekenyes, Hungary. Time evolution of the biologically effective doses, cumulated daily doses and daily dose-profiles have been measured. Measurements were undertaken not only in different water depths but also just above the water surface (15 cm height) and also on the beach. The exponential attenuation of daily doses in water has been confirmed. Although the values of H-T7 above the water's surface and on the beach were similar, the dose rates were very different between the two sides of the water surface, i.e. just under it (at 5 cm depth) and above it (at 15 cm height). Their ratio has been found to be dependent on the zenith angle with a maximum of not more than 0.5, and at higher zenith angles it is about 0.3. [TOP OF PAGE]

  208. A moderately halophilic Vibrio from a Spanish saltern and its lytic bacteriophage. Goel,U., Kauri,T., Ackermann,H.W., Kushner,D.J. (1996). Can. J. Microbiol. 42:1015-1023. A number of bacteria and their phages were isolated from a saltern near Alicante, Spain. One isolate, Vibrio B1, a moderate halophile that is probably a strain of Vibrio costicola, was host to a lytic phage, UTAK. Studies of the host bacterium included the effects of salt concentrations on the action of a number of inhibitory agents. Phage UTAK has a head, a tail, and a baseplate. It contains 80 kbp of double-stranded DNA with no unusual bases. It was stable for long periods in the absence of high salt concentrations and even in distilled water. Salt concentrations had little effect on adsorption of UTAK to its host but resulted in considerable changes in burst size. It appears that phages of halophilic and salt-tolerant eubacteria, and also of some marine bacteria, have much lower salt requirements for stability than the phages of halophilic archaebacteria. Our results suggest that ionic controls of phage replication in these eubacteria may differ from those of growth. [TOP OF PAGE]

  209. [Phagolysates of cyanobacteria: their biocidal properties and use]. Gol'din,E.B., Mendzhul,M.I. (1996). Mikrobiol. Zh. 58:51-58. Data on the biological activity of cyanobacterial phagolysates were obtained in experiments. They concern the organisms of different evolutional level, such as some conventional pathogenic bacteria, plant and root parasitic nematodes and phytophagous insects. The authors suppose the specific mechanism of biocidal and inhibitory action of cyanobacteria and their phagolysates in respect to different living systems. These facts are very important for the elaboration of practical aspects of algal metabolites employment in agriculture and medicine. [TOP OF PAGE]

  210. Viral lysis and bacterivory as prokaryotic loss factors along a salinity gradient. Guixa-Boixareu,N., Calderon-Paz,J.I., Heldal,M., Bratbak,G., Pedros-Alio,C. (1996). Aquat. Microb. Ecol. 11:215-227. We estimated prokaryotic mortality due to viruses and bacterivores through salinity gradients in 2 solar salterns. In each saltern system, successive ponds provided steady state environments with a range of salinities from 37 to 372ppt. Prokaryotic and viral abundance increased with salinity, reaching about 10 super(8) prokaryotic cells ml super(-1) and 10 super(9) virus-like particles (VLP) ml super(-1) at salinities higher than 250ppt. Prokaryotic doubling times became longer than 2 d above 250ppt salinity until the end of the gradient. Bacterivory accounted for all the production at lower salinities but it was found to be zero at the highest salinities. The percentage of visibly infected cells was not different among the ponds where infected cells could be detected and it was always lower than 4%. From the percentage of infected cells and using conversion factors from the literature we estimated rates of prokaryotic mortality due to viral lysis: about 0.6 to 2 x 10 super(6) prokaryotes m super(-1) were lysed daily by the viruses in the salterns. This number represented a low percentage of prokaryotic abundance and production compared to the prokaryotic losses due to bacterivores (0.2 to 4 x 10 super(7) bacteria ml super(-1) d super(-1)). However, viral production reached values higher than 10 super(8) VLP ml super(-1) d super(-1) above 250ppt salinity, due to the large burst size (200 viruses cell super(-1)) found in a particular morphotype of prokaryotes, the square archaea. These archaea represented more than 25% of the prokaryotic assemblage above 250ppt salinity. At this point they became the prokaryotic morphotype with the largest percentage of infected cells (1 to 10% of square archaea with visible phages inside). A lemon-shaped virus (similar to one described for some other groups of archaea) was found infecting square archaea, its abundance increased in the saltiest ponds together with that of the square archaea. In this system viruses did not exert a strong control over the prokaryotic abundance and growth rate. [TOP OF PAGE]

  211. Abundance of viruses in deep oceanic waters. Hara,S., Koike,I., Terauchi,K., Kamiya,H., Tanoue,E. (1996). Mar. Ecol. Prog. Ser. 145:269-277. Vertical distributions of bacteria and viruses were investigated in the oceanic stations located in subarctic (Stn A) and subtropical (Stn B) areas of the Pacific using the direct count technique and transmission electron microscopy. Small DAPI-positive, virus-like particles (VLP) were found to be distributed throughout the water column down to 5000 m at both of the stations. The abundance of VLP ranged from 38 x 105 ml-1 at 50 m depth to 0.6 x 105 ml-1 at 5000 m depth at Stn A. The ratio of VLP to bacteria-like particle (BLP) ranged from 1.1 to 7.4 at Stn A and 1.0 to 8.7 at Stn B in the entire water column. The maximum ratio was recorded at Stn B from the deepest sample, collected at a depth of 5000 m. The electron microscopic investigation indicated that the major proportion of VLP were probably viruses. [TOP OF PAGE]

  212. Occurence of lysogenic bacteria in marine microbial communities as determined by prophage induction. Jiang,S.C., Paul,J.H. (1996). Mar. Ecol. Prog. Ser. 142:27-38. Viruses are abundant and dynamic members of the marine microbial community, and it is important to understand their role in the ecology of natural microbial populations. We have previously found lysogenic bacteria to be a significant proportion (43%) of the cultivable heterotrophic microbial population. As the majority of marine bacteria are not cultivable using standard plating methods, we measured the proportion of marine lysogenic bacteria in natural communities by prophage induction. Mitomycin C, UV radiation, sunlight, temperature and pressure were used to induce prophage in lysogenic bacteria from estuarine, coastal and oligotrophic offshore environments. To determine if hydrocarbon pollutants may cause the induction of marine lysogens, aromatic and aliphatic hydrocarbons (including Bunker C #6 fuel oil, phenanthrene, naphthalene, pyrene, and trichloroethylene) were also used as inducing agents. Induction was most often found in estuarine environments, where viral direct counts increased from 128.8 to 345% of the uninduced control, resulting in mortality of 10.5 to 67.3% (average 34%) of the bacterial population. Up to 38% of the bacterial population was lysogenized in estuarine environments, as calculated from an average burst size. Microbial populations from oligotrophic offshore environments were inducible at 3 of 11 stations sampled. Eight of the 11 samples (73%) treated with polyaromatic hydrocarbons resulted in prophage induction in natural populations. Time series analysis was also conducted in 2 samples induced by mitomycin C from the Atlantic Ocean near the coast of North Carolina, USA. For both samples, significant decreases in bacterial numbers were detected in treated samples after 8 h of incubation. A significant increase of viruses was detected at 8 h at one station and at 24 h at the other station after induction. This study indicates that natural lysogenic populations are sensitive to a variety of inducing agents, and induction occurs more frequently in coastal and estuarine environments than offshore environments. [TOP OF PAGE]

  213. Evidence that the hanA gene coding for HU protein is essential for heterocyst differentiation in, and cyanophage A-4(L) sensitivity of, Anabaena sp. strain PCC 7120. Khudyakov,I., Wolk,C.P. (1996). Journal of Bacteriology [J. BACTERIOL. ] 178:3572-3577. The highly pleiotropic, transposon-generated mutant Anabaena sp. strain PCC7120 exhibits slow growth, altered pigmentation, cellular fragility, resistance to phage A-4(L), and the inability to differentiate heterocysts. Reconstruction of the transposon mutation in the wild-type strain reproduced the phenotype of the original mutant. Sequencing of the flanking DNA showed that the transposon had inserted at the beginning of a gene, which we call hanA, that encodes Anabaena HU protein. Mapping of the transposon insertion by pulsed-field gel electrophoresis showed that hanA is located at ca. 4.76 Mb on the physical map of the chromosome and is transcribed clockwise. Repeated subculturing of of filament fragmentation, presumably because of one or more compensatory mutations; however, the mutant retained its A-4(L) super(r) Het super(-) phenotype. The mutation in strain be complemented by a fragment of wild-type DNA bearing hanA as its only open reading frame. [TOP OF PAGE]

  214. Modification of the polyethylene glycol 6000 precipitation method for recovering human and indicator viruses from oysters and mussels. Lewis,G.D., Hough,A., Green,D.H., Hay,J.E., Ferguson,L.R. (1996). N. Z. J. Mar. Fresh. Res. 30:443-447. Human viruses are a common contaminant of shellfish affected by human sewage wastes. They are difficult to detect as they are not easily separated from shellfish tissue. This paper describes a modification of the polyethylene glycol (PEG) precipitation technique for recovery of enteroviruses and F-specific bacteriophages from the Pacific oyster (Crassostrea gigas) and the green-lipped mussel (Perna canaliculus). Modifications adopted were the use of only the digestive gland tissue for virus extraction, resuspension of the primary PEG pellet in 4 volumes of eluent, and the introduction of a secondary PEG precipitation to reconcentrate the virus containing extract. The recovery rate of the virus extraction process was not affected by introduction of the secondary concentration step (overall recovery remained at 60-70% of the virus input). The advantages of reduction of tissue residue in the extract, smaller final volume, and the ability to process 2-3 times the number of individual shellfish for the same effort, improve the practicality of the method. [TOP OF PAGE]

  215. Wastewater treatment and elimination of pathogens: new prospects for an old problem. Lopez-Pila,J.M., Dizer,H., Dorau,W. (1996). Microbiologia 12:525-536. Although the development of wastewater treatment technology is more than one hundred years old, most wastewater treatment plants existing today do not eliminate pathogens satisfactorily. Even in highly developed nations, receiving waters, serving in many cases as drinking water resources, are contaminated with pathogens. Surface waters also contain large concentration of phosphate due to long lasting wastewater discharges. Cyanobacteria and algal overgrowth is the consequence. Present drinking water technology only partially overcomes the pollution; it can not be ruled out that drinking water originating from polluted resources contains pathogens. This situation frequently goes on unnoticed because current indicator organisms are not representative for all pathogens. As studies have shown that small concentrations of pathogens also pose a risk for the consumer health, this state of affairs is a matter of concern. Microfiltration technology is able to significantly eliminate bacteria and protists from wastewater. Viruses, although smaller than the pore size of the filters, are reduced too because, in wastewater, they are frequently bound to larger particles. If the microfiltration of wastewater is preceded by the addition of coagulants for the precipitation of phosphate, the precipitate will be retained by the filter. The effluent obtained contains very low concentrations of phosphate. As viruses also adsorb to the precipitate, the amount of viruses eliminated increases and with increasing amounts of coagulant they become undetectable. [TOP OF PAGE]

  216. Effects of viruses on nutrient turnover and growth efficiency of noninfected marine bacterioplankton. Middelboe,M., Jorgensen,N.O.G., Kroer,N. (1996). Appl. Environ. Microbiol. 62:1991-1997. The effects of virus infection and lysis of a marine Vibrio sp. on C, N, and P turnover and the growth efficiency of noninfected bacterioplankton were studied in a series of dilution cultures. The cultures were enriched with various sources of organic matter and N and P. The growth of the Vibrio host and the growth of the natural bacterioplankton were measured by immunofluorescence and 4',6-diamidino-2-phenylindole staining methods, respectively. Lysis products resulting from infection of the Vibrio sp. caused an increase in metabolic activity and cell production by the noninfected bacterioplankton. In P-limited cultures, the addition of viruses increased the uptake of dissolved organic carbon by 72% and the potential alkaline phosphatase activity by 89% compared with control cultures without viruses. Our data suggest that input of available phosphorus through virus-induced Vibrio lysates occurred, which caused an increase in the bacterial nutrient uptake. The growth efficiency of noninfected bacteria was reduced in the presence of viruses compared with the control without viruses (growth efficiencies, 0.08 plus or minus 0.03 and 0.24 plus or minus 0.02, respectively). We suggest that the decrease in growth efficiency may be explained by an increase in bacterial energy demand associated with extracellular degradation of polymeric organic nitrogen and phosphorus in cell lysates. [TOP OF PAGE]

  217. Napravleniya i rezul'taty issledovanij Otdela Morskoj Sanitarnoj, gidrobiologii [Trends and results of investigations made by the Marine Sanitary Hydrobiology Department]. Mironov,O.G. (1996). Ehkologiya Morya 85-92. Scientific trends in marine sanitary hydrobiological researches cover interactions of marine organisms and their communities with pollution as a part of common nature processes of substance transformation and energy transport in marine environment. Knowledge of the marine biota role in these processes opens the possibility to use marine organisms and their communities expediently in anti-pollution struggle, in particular biotesting, biomonitoring and developing hydrobiological cleaning systems for polluted sea waters. 30-years of investigation by the Marine Sanitary Hydrobiology Department of the Institute of Biology of the Southern Seas (Ukraine) data on the influence of oil and oil products on Black Sea organisms and to identify their susceptibility to toxicants, regularities in number, species composition, distribution, biochemical peculiarities of oil-oxidizing microorganisms, hydrocarbon accumulation by marine hydrobionts at moderate, tropical and polar latitudes of the World Ocean. The obtained materials were used in the International Project on Biomonitoring of the Mediterranean Basin's Oil Pollution, for elaborating methods and putting into practice different seawater hydrobiological cleaning systems to improve the water area. In future a common study direction 'interaction' will remain however the rest area will be narrowed significantly - investigations will mainly be run at the Azov Sea and Crimean Shelf zone. Microbiological studies will be wider due to studies of the smallest forms of bacterioplankton relating to viruses and phages. In a sanitary-biological aspect, meiobenthos will be considered as an intermediate between bacteriobenthos and macrozoobenthos. Also, toxicological investigations will be continued, but the number of biological objects will be restricted by those species which are of interest as elements for the seawater hydrobiological cleaning systems or elements for pollution biotesting. [TOP OF PAGE]

  218. Marine bacteriophage reproduction under nutrient-limited growth of host bacteria. II. Investigations with phage-host system [H3: H3/1]. Moebus,K. (1996). Mar. Ecol. Prog. Ser. 144:13-22. When host bacterium H3 is cultivated in artificial seawater at a concentration of 0.6 mg organic nutrients ml-1, its reaction to infection by phage H3/1 changes dramatically with the duration of incubation before phage attack. Cells infected when still in their logarithmic growth phase rapidly produce progeny phage until breakdown of the phage-sensitive population. For cells infected after entering the stationary phase, rate and extent of phage propagation by resting cells decreases for some time, but both parameters rather suddenly increase again for cells infected after prolonged incubation. Phage production may then reach the same level attained by cells infected during logarithmic growth phase; although, with increasing phage concentration, resting cells very effectively become protected from phage attack by pseudolysogeny. This course of events is mainly influenced by the method of incubation of the host (shaken vs still), by the age of the cells before infection, and presumably by changes in physiological traits of the bacteria when serially subcultured for extended periods of time. The reduction in volume of bacterial culture by repeated withdrawal of aliquots was found to be of minor importance; however, phage production was measurably affected by the transfer of cells to fresh receptacles. With cells which entered their stationary phase up to 36 h before infection, an initial phage concentration of between 10 and 10-3 PFU (plaque forming units) ml-1 was found to determine the extent, but not the rate, of phage production. The aforementioned observations were also made with cells starved for 3, 8, and 22 additional days before inoculation, except with initial PFU concentrations of 10 and 10-2 PFU ml-1, when an appreciable increase in phage production was found. In cell suspensions seeded with phage 48 d after set up of the experiment, the highest phage production was found with the lowest initial phage concentration and vice versa. This finding, i.e. the inverse relationship between production and initial concentration, is not in agreement with any of the current hypotheses concerning bacteriophage ecology. [TOP OF PAGE]

  219. Marine bacteriophage reproduction under nutrient-limited growth of host bacteria. I. Investigations with six phage-host systems. Moebus,K. (1996). Mar. Ecol. Prog. Ser. 144:1-12. Bacteriophage reproduction was investigated with 6 phage-host systems (PHS) isolated from the North Sea near Helgoland, Germany, with the hosts adapted to growth at 6 or 0.6 mg organic nutrients 1-1. For 5 of the PHS, similarities in production were observed to depend upon the time of infection during a transition period which included the last hours of the logarithmic growth phase and the first 1 to 2 d of the stationary growth phase of the host bacteria. Over this period the extent and/or the rate of phage production d-1 decreased greatly. After longer incubation before addition of phage, the relative ability of host cells to propagate phage either ceased (3 PHS) or was regained (1 PHS) or remained the same as during the transition period in regard to final phage concentrations (1 PHS). The remaining PHS showed no phage reproduction at the low nutrient concentration. With phage-resistant mutant bacteria serving as competitors for nutrients, phage production was drastically reduced. The present findings are in agreement with observations concerning concentrations of infective virions in fresh seawater samples. They failed, however, to provide evidence for the hypothesis that release of mature phage in starving marine bacteria is delayed until sufficient nutrients become available. [TOP OF PAGE]

  220. Occurrence of a temperate cyanophage lysogenizing the marine cyanophyte Phormidium persicinum. Ohki,K., Fujita,Y. (1996). J. Phycol. 32:365-370. A temperate cyanophage was found to lysogenize the marine cyanophyte Phormidium persicinum (Reinke) Gom. (Provasoli strain). The lytic cycle was induced by the addition of mitomycin C or by brief illumination with ultraviolet light. The lytic process observed under the electron microscope showed that phage particles appeared in a nucleoplasm region 15 to 24 h after the addition of mitomycin C. The induction of the lytic process occurred simultaneously in almost all cells of every trichome. Matured phage particles were released to the medium 30 to 50 h after the addition of mitomycin C Phage particles isolated from algal lysates had a polyhedral head (about 40 nm in diameter) with a long (about 300 nm) and noncontractile tail. The most abundant protein, presumably a structural protein, had an apparent molecular mass of about 38 kDa. The genome size estimated from restriction analysis was about 50 kbp. Phage DNA was digested with several restriction endonucleases including Sau3AI and DpnI. However, MboI failed to digest the pha DVA, suggesting that the phage DNA is highly methylated. Southern blot analysis suggested that some part of the phage was in the lytic cycle in algal cells growing under normal conditions. A possible role of temperate cyanophages in the regulation of cyanophyte populations in the marine environment is discussed. [TOP OF PAGE]

  221. Viruses and DNA in marine environments. Paul,J.H., Kellogg,C.A., Jiang,S.C. (1996). pp. 115-124. In In Colwell,R.R., Simidu,U., and Ohwada,K. (eds.), Microbial Diversity in Time and Space. Plenum Press, New York. [TOP OF PAGE]

  222. Mycobacteriophage specific for the Mycobacterium tuberculosis complex. Pearson,R.E., Dickson,J.A., Hamilton,P.T., Little,M.C., Beyer,Jr.W.F. (1996). Becton, Dickinson and Company. 508004(5,582,969). Franklin Lakes, NJ. Mycobacteriophage DS6A has been characterized and found to specifically infect all species of the TB complex, without any detectable infection of mycobacteria species other than those of the TB complex. DNA sequence analysis revealed several potential open reading frames, including one encoding a protein analogous to gp37 of mycobacteriophage L5 and a second encoding a protein with significant homology to the S. coelicolor DNA polymerase b subunit. Based on the DNA sequence analysis, cloning sites can be identified for insertion of reporter genes, making DS6A useful as a reporter phage for specific detection and identification of species of the TB complex. [TOP OF PAGE]

  223. The Role of Transduction and Pseudolysogeny in Bacteriophage-host Interactions in a Natural Freshwater Environment. Ripp,S. (1996). Oklahoma State Univ., Stillwater, OK, USA. Scope and method of study. Bacteriophages occur in high numbers in environmental ecosystems, and are thus significant mediators of microbial survival and activities. However, the dynamic interactions occurring between microbial populations and bacteriophages in situ has been largely ignored, with our current understanding relying on studies performed with well-fed laboratory grown host strains. It was our purpose in this study to determine phage-host interactions under the more typical nutrient-depleted conditions commonly encountered by a cell in a natural environment. We have chosen a small freshwater lake as our test site and in addition have employed continuous-culture chemostats as a way to maintain and study starved cell populations and their consequent interactions with bacteriophages. Findings and conclusions. As a result of these studies, we have encountered a phenomenon that has long been known but little studied-- pseudolysogeny. Pseudolysogeny refers to a bacteriophage-host cell interaction whereby the nucleic acid of the phage, upon infection of an appropriate host cell, does not integrate itself into the host's genome, as would occur in a typical lysogenic response. Nor does the phage initiate cell lysis, as it would in a lytic response. Rather, the phage nucleic acid simply resides within the cell in a non-active form. It is thought that, due to the cell's highly starved state, there isn't sufficient energy available for the phage to initiate a true lysogenic or lytic response. However, upon nutrient addition and subsequent energy level increase, the pseudolysogenic response ceases and either true lysogeny or the lytic response ensues. [TOP OF PAGE]

  224. Temporal and spatial dynamics of Synechococcus spp. and Micromonas pusilla host-viral systems. Rodda,K.M. (1996). University of Texa at Austin. [TOP OF PAGE]

  225. Unusual contribution of 2-aminoadenine to the thermostability of DNA. Sagi,J., Szakonyi,E., Vorlickova,M., Kypr,J. (1996). J Biomol Struct Dyn 13:1035-1041. The poly(dA-dU) and poly(dI-dC) duplexes have very similar thermostabilities (Tm). This similarity extends also to the pyrimidine 5-methyl group-containing poly(dA-dT) and poly(dI-m5dC). The differences between chemical structures of the A:U and I:C or the A:T and I:m5C base-pairs seem to be unimportant for the thermostability of the DNA. However, on the insertion of an amino group into position 2 of the purines the similarities disappear. Thermostabilities of poly(n2dA-dU) and poly(dG-dC) as well as the poly(n2dA-dT) and poly(dG-m5dC) are radically different. This is also the case with their other 5-substituted pyrimidine-containing derivatives, the 5-ethyl, 5-n-butyl and 5-bromo analogues. The G:C-based polynucleotides are more stable by an average of 40 degrees C than the n2A.U-based ones. Poly(dA,n2dA-dT)-s containing various proportions of A and n2A as well as the natural DNA of S-2L cyanophage that contains n2A bases instead of A were also studied. It was found that dependence of Tm on the n2A-content was non-linear and that the lower Tm is not the consequence of a particular nucleotide sequence. The possible structural reasons for the lower thermostabilization of these B-DNAs by the n2A:T base-pair as compared to the G:C are discussed. [TOP OF PAGE]

  226. Characterization of planktonic virus-like particles in a French mountain lake: Methodological aspects and preliminary results [French]. Sime-Ngando,T., Mignot,J.P., Amblard,C., Bourdier,G., Desvilettes,C., Quiblier Llobers,C. (1996). Annales de Limnologie 32:259-263. In this short communication, we describe a simple method to ultracentrifuge and concentrate planktonic virus-like particles, for their examination with a transmission electron microscope. A description of different morphotypes of particles clearly assimilable to viruses is made in plankton samples from the euphotic layer of a eutrophic lake (Lake Aydat), during its spring and summer development. The particles possess a tail and a 6-sided icosahedral capsid-head, with dimensions similar to those of phages already described in marine systems. The diversity of viral forms and their abundance (10 fold higher than that of bacteria) in Lake Aydat, suggests a significant role in controlling bacterial number in lakes. [TOP OF PAGE]

  227. [Caracterisation des particules virales planctoniques dans un lac du Massif Central francais: Aspects methodologiques et premiers resultats] Characterization of planktonic virus-like particles in a French mountain lake: Methodological aspects and preliminary results. Sime-Ngando,T., Mignot,J.P., Amblard,C., Bourdier,G., Desvilettes,C., Quiblier-Lloberas,C. (1996). Annales de Limnologie 32:259-263. In this short communication, we describe a simple method to ultracentrifuge and concentrate planktonic virus-like particles, for their examination with a transmission electron microscope. A description of different morphotypes of particles clearly assimilable to viruses is made in plankton samples from the euphotic layer of a eutrophic lake (Lake Aydat), during its spring and summer development. The particles possess a tail and a 6-sided icosahedral capsid-head, with dimensions similar to those of phages already described in marine systems. The diversity of viral forms and their abundance (10 fold higher than that of bacteria) in Lake Aydat, suggests a significant role in controlling bacterial number in lakes. [TOP OF PAGE]

  228. Virus-like particles in Polysporoplasma mugilis (Protozoa:Myxosporea), parasitic in a marine fish (Liza aurata L.). Sitja-Bobadilla,A., Alvarez-Pellitero,P. (1996). International Journal for Parasitology 26:457-459. Virus-like particles (VLP) were observed in the capsulogenic cells of the spores of Polysporoplasma mugilis, a myxosporean parasite in the trunk kidney of Liza aurata. Transmission electron microscopy revealed icosahedral, electron-dense cored VLP of 18-20 nm in diameter. By their ultrastructural characteristics and cytoplasmic position, these VLP are related to the Picornaviridae. The VLP were densely packed inside membraned vacuoles. VLP were found neither in other developmental stages, nor in other parts of the spore, nor in the host tissue. This is the third record of VLP in protozoans parasitic in fish, and the first one from the Myxosporea. [TOP OF PAGE]

  229. Abundance and production of bacteria and viruses in the Bering and Chukchi sea. Steward,G.F., Smith,D.C., Azam,F. (1996). Mar. Ecol. Prog. Ser. 131:287-300. The distribution, abundance, and production of viruses and bacteria were investigated during an August to September 1992 cruise aboard the RV 'Alpha Helix' in the Bering and Chukchi Seas. Viruses were abundant in seawater samples at all stations (109 to 1010 l-1) and exceeded the bacteria concentration by an order of magnitude on average. Virus-like particles and bacteria were also observed in the pore water of a sediment sample at 27 and 2.1 ´ 109 l-1, respectively. The concentrations of viruses and bacteria in pelagic samples were correlated (r = 0.83, n = 43). In a detailed depth profile from the deepest and northern most station (72° N), bacteria and viruses displayed subsurface maxima in the upper 100 m. Below 100 m, the concentrations declined, but were detectable even in the deepest-collected samples (402 m). Integrated bacterial biomass estimates were similar to results from a previous study in this area, but bacterial production measurements ranging from 0.3 to 0.45 g C m-2 d-1 were an order of magnitude higher. Production rates of bacterial viruses (also known as bacteriophages or simply phages) measured by radiolabeling ranged from 0.5 to 4.2 ´ 109 viruses l-1 d-1, which are similar to previous estimates for temperate coastal waters. The production measurements indicated turnover times ranging from 0.4 to 17 d for bacteria and maximum estimates of 1.2 to 15 d for bacterial viruses. Viral mortality of bacteria was estimated from the frequency of visibly infected cells (FVIC) and flagellate grazing was calculated from flagellate and bacterial abundances together with an assumed flagellate clearance rate. Overall, estimated viral lysis was roughly comparable to estimated grazing by flagellates as a source of bacterial mortality. Averaged over the water column, viral mortality of bacteria in the Chukchi Sea was estimated to be 23% of the bacterial production at two southern stations and approximately 10% at two northern stations. FVIC was correlated with bacterial production (r = 0.75, n=18) and specific growth rate (r = 0.74, n=18), but not with bacterial abundance (r = 0.22, n = 27). These data show viruses to be an ubiquitous and dynamic feature and a significant source of bacterial mortality in Arctic marine microbial communities. The implications of bacterial and viral production for C and N cycling in the Chukchi Sea are discussed. [TOP OF PAGE]

  230. The effect of cyanophages on Synechococcus spp. during a bloom in the western Gulf of Mexico. Suttle,C.A., Chan,A.M., Rodda,K.M., Short,S.M., Weinbauer,M.G., Garza,D.R., Wilhelm,S.W. (1996). EOS 76 (suppl.):OS207-OS208 [TOP OF PAGE]

  231. Viruses as biological control agents for blooms of marine phytoplankton. Suttle,C.A. (1996). pp. 71-76. In AnonymousProceedings of the Brown Tide Summit, 20-21 October, 1995. New York Sea Grant Institute???, [TOP OF PAGE]

  232. Potential significance of lysogeny to bacteriophage production and bacterial mortality in coastal waters of the Gulf of Mexico. Weinbauer,M.G., Suttle,C.A. (1996). Appl. Environ. Microbiol. 62:4374-4380. The potential effect that induction of lysogenic bacteria has on bacteriophage production and bacterial mortality in coastal waters was investigated, and we present estimates for the percentage of lysogenic cells in a natural aquatic bacterial community. Various concentrations of mitomycin C and exposure times to UV C radiation (UV-C) (wavelength of 254 nm) were used to induce the lytic cycle in lysogenic cells of natural communities of marine bacteria. UV-C treatment occasionally resulted in phage production, but phage production induced by UV- C was always less than that caused by the addition of mitomycin C. There was no evidence that high growth rates of bacteria resulted in lysogenic phage production. The burst size of cells induced by mitomycin C was determined by transmission electron microscopy and ranged from 11 to 45. Dividing the induced phage production by the burst size provided an estimate of the number of lysogenic bacterial cells, which ranged from 0.07 to 4.4% (average, 1.5%) of the total bacterial population. The percentages of lysogenic bacteria that were induced by mitomycin C were similar for samples collected nearshore from the pier of the Marine Science Institute (chlorophyll a, 1.6 to 2.9 mu-g liter-1) and in relatively oligotrophic water (chlorophyll a, 0.2 to 0.9 mu-g liter-1) collected 25 to 100 km offshore. By using a steady-state model, if all lysogenic bacteria were induced simultaneously, 0.14 to 8.8% (average, 3.0%) of the total bacterial mortality would result from induction of lysogenic cells. If mitomycin C induces all or the majority of lysogenized cells, our results imply that lysogenic phage production is generally not an important source of phage production or bacterial mortality in the coastal waters of the western Gulf of Mexico. [TOP OF PAGE]

  233. The effects of nutrient limitation on the kinetics of cyanophage infection of the oceanic picoplankter Synechococcus sp. WH7803. Wilson,S.H., Carr,N.G., Mann,N.H. (1996). J. Phycol. 32:506-516. Phycoerythin-containing Synechococcus species are considered to be major primary producers in nutrient-limited gyres of subtropical and tropical oceanic provinces, and the cianophages that infect them are thought to influence marine biogeochemical cycles. This study begins an examination of the effects of nutrient limitation on the dynamics of cjanophage/Synechococcus interactions in oligotrophic environments by analyzing the infection kinetics of cyanophage strain S-P1kf2 (Cyanomyoviridae isolated from coastal water off Plymouth, UK) propagated on Synechococcus sp. WH7803 grown in either phosphate-deplete or phosphate-replete conditions. When the growth of Synechococcus sp. WH7803 in phosphate deplete medium was followed after injection with cyanophage, an 18-h[???} delay in cell Iysis was observed when compared to a phosphate-replete control. Synechococcus sp. WH7803 cultures grown at tu10 different rates (in the same nutritional conditions) both lysed 24 h postinfection, ruling out growth rate itself as a factor in the delay of cell lysis. One-step growth kinetics of S-PA\/12 propagated on host Synechococcus sp. W'H7803, grow in phosphate deplete and-replete media, revealed an apparent 80% decrease in burst size in phosphate-deplete growth conditions, but phage adsorption kinetics of S-PM2 under these conditions showed no differences. These results suggested that the cyanophages established lysogeny in response to phosphate-deplete growth of host cells. This suggestion was supported by comparison of the proportion of infected cells that lysed under phosphate-replete and-deplete conditions, which revealed that only 9.3% of phosphate-deplete infected cells lysed in contrast to 100% of infected phosphate-replete cells. Further studies with two independent cyanophage strains also revealed that only approximately 10% of infected phosphate-deplete host cells released progeny cyanophages. These data strongly support the concept that the phosphate status of the Synechococcus cell will have a profound effect on the eventual outcome of phage-host interactions and will therefore exert a similarly extensive effect on the dynamics of carbon flow in the marine environment. [TOP OF PAGE]

  234. The effect of phosphate status on the kinetics of cyanophage infection in the oceanic cyanobacterium Synechococcus sp. WH7803. Wilson,W.H., Carr,N.G., Mann,N.H. (1996). J. Phycol. 32:506-516. Phycoerythrin-containing Synechococcus species are considered to be major primary producers in nutrient-limited gyres of subtropical and tropical oceanic provinces, and the cyanophages that infect them are thought to influence marine biogeochemical cycles. This study begins an examination of the effects of nutrient limitation on the dynamics of cyanophage/Synechococcus interactions in oligotrophic environments by analyzing the infection kinetics of cyanophage strain S-PM2 (Cyanomyoviridae isolated from coastal water off Plymouth, UK) propagated on Synechococcus sp. WH7803 grown in either phosphate-deplete or phosphate-replete conditions. When the growth of Synechococcus sp. WH7803 in phosphate-deplete medium was followed after infection with cyanophage, an 18-h delay in cell lysis was observed when compared to a phosphate-replete control. Synechococcus sp. WH7803 cultures grown at two different rates (in the same nutritional conditions) both lysed 24 h postinfection, ruling out growth rate itself as a factor in the delay of cell lysis. One- step growth kinetics of S-PM2 propagated on host Synechococcus sp. WH7803, grown in phosphate-deplete and- replete media, revealed an apparent 80% decrease in burst size in phosphate-deplete growth conditions, but phage adsorption kinetics of S-PM2 under these conditions showed no differences. These results suggested that the cyanophages established lysogeny in response to phosphate-deplete growth of host cells. This suggestion was supported by comparison of the proportion of infected cells that lysed under phosphate-replete and-deplete conditions, which revealed that only 9.3% of phosphate-deplete infected cells lysed in contrast to 100% of infected phosphate replete cells. Further studies with two independent cyanophage strains also revealed that only approximately 10% of infected phosphate-deplete host cells released progeny cyanophages. These data strongly support the concept that the phosphate status of the Synechococcus cell will have a profound effect on the eventual outcome of phage-host interactions and will therefore exert a similarly extensive effect on the dynamics of carbon flow in the marine environment. [TOP OF PAGE]

  235. Virological quality of the Ria de Aveiro: Validity of potential microbial indicators. Alcantara,F., Almeida,M.A. (1995). Netherlands Journal of Aquatic Ecology 29:419-425. The summer occurrence of human enteroviruses and rotaviruses in the bacteriologically clean area of the Ria de Aveiro, a coastal marine lagoon, prompted the question of the assessment of the virological quality of recreational waters and shellfish raising beds. Enteroviruses were present in surface water at a density of 3 pfu 10 l-1 and were accumulated in sediments and, especially, in cockles where they reached concentrations 2 to 3 10log units greater. Rotaviruses were detected at one 10log unit below the density of enteroviruses in sediments and cockles and were not detected in water. Four bacteriophage systems were assayed as indicators of human enteric viruses: somatic coliphages of E. coli C, sexual and sexual-RNA coliphages plated on Salmonella WG49 and phages against Bacteroides fragilis HSP40. The results obtained from 2 lagoon stations sampled in summer, autumn and winter showed that the four systems failed to indicate the presence of enteroviruses and rotaviruses in water, sediment and shellfish samples. The absence of phages of B. fragilis HSP40 in all types of samples taken from the lagoon, but not from the residual waters of the treatment station, suggests that they may suffer a strong negative pressure in this ecosystem as their proportion to the coliphages in the cockles deviated strongly from the ratio of 1:100 to 1:1000 observed at the sewage outfall. In fact, no correlation was observed between these phages and enteric viruses or coliphages. Alternatively, it is possible that the importance of diffuse faecal pollution and the interference of faecal pollutants of animal origin, including migratory sea birds which are abundant in winter, can alter the proportions of the faecal bacteriophages beyond recognition. It is apparent that bacteriophage monitoring of the health risk linked to the occurrence of viruses in the marine environment is not yet fully resolved, what may leave viral quality assessment dependent on direct detection of human enteric virus. [TOP OF PAGE]

  236. Amplification of DNA polymerase gene fragments from viruses infecting microalgae. Chen,F., Suttle,C.A. (1995). Appl. Environ. Microbiol. 61:1274-1278. Nested PCR using three highly degenerate primers was used for amplification and identification of the DNA polymerase (pol) genes from viruses which infect three genera of microalgae. Group-specific primers (AVS1, AVS2) were designed based on inferred amino acid sequences that were unique to the DNA pol genes of viruses (PBCV-1 and NY-2A) infecting an endosymbiotic Chlorella-like algae (Chlorophyceae), and a virus (MpV-SP1) which infects the photosynthetic flagellate Micromonas pusilla (Prasinophyceae). As well, a nested primer (POL) was designed based on the highly conserved amino acid sequence YGDTDS found in most B-family (*-like) DNA pol genes. These primers were used to amplify DNA from the three viruses PBCV-1, NY-2A and MpV-SP1 for which the primers were designed, as well as eight other clonal isolates of genetically distinct viruses which infect M. pusilla and viruses which infect Chrysochromulina spp., (Prymnesiophyceae) suggesting that these are a group of related viruses. The primers could also be used to amplify DNA from natural virus communities. In contrast, a product was not produced when DNA from viruses which infect the marine brown algae Ectocarpus siliculosis and Feldmannia sp. (Phaeophyceae) was used, suggesting that these viruses may not be closely related to those infecting microalgae. The primers could also be used to amplify DNA from natural virus communities. Our results indicate that nested PCR, even under low stringency conditions, can be used as a rapid method to verify the presence in seawater of a group of related viruses which infect microalgae. Sequence analysis of these fragments should provide information on the genetic diversity and possibly the phyletic relationships among these viruses. This is the first example of a PCR-based technique designed to detect viruses which infect eukaryotic algae. [TOP OF PAGE]

  237. Genetic diversity of algal viruses which lyse the photosynthetic picoflagellate Micromonas pusilla (Prasinophyceae). Cottrell,M.T., Suttle,C.A. (1995). Appl. Environ. Microbiol. 61:3088-3091. The genetic similarity among eight clones of Micromonas pusilla virus (MpV) isolated from five geographic locations was measured by DNA hybridization. Our objective was to explore the existence of genetically distinct populations of MpV by comparing the similarity among MpVs isolated from a single water sample to the similarity among viruses isolated from geographically distant locations. The highest and lowest similarities we observed were 70% plus or minus 1.1% (mean plus or minus standard error [SE], n = 3) for virus strains SP1 and SP2 isolated from a California coastal water sample and 13% plus or minus 1.9% for strains SP2 and PB6; the latter was isolated from New York estuarine water. However, the similarity between MpV isolated from a single water sample was not always greater than the similarity between viruses isolated from different locations. Viruses PB7 and PB8 were isolated from a single New York estuarine sample but were only 16% plus or minus 0.5% similar, whereas PB7 was quite similar (43% plus or minus 2.9%) to PL1, a virus from Texas coastal water. Overall, the similarity among MpVs isolated from a single geographic location, 34% plus or minus 12.6% (mean plus or minus SE, n = 4), was not significantly different from the similarity among MpVs isolated from geographically distant locations, 26.6% plus or minus 2.7% (mean plus or minus SE, n = 24) (P = 0.92, Mann-Whitney U test). Clones of MpV were more similar to each other than they were to the related algal virus PBCV-1, and three groups of MpVs consisting of (i) PL1, SG1, PB6, and PB7, (ii) PB8, and (iii) GM1, SP1, and SP2 were resolved. The genetic variation among MpVs isolated from a single water sample was as large as the variation between viruses isolated from different oceans. If MpVs within a geographic location share genetic characteristics not shared with MpVs from geographically distant locations, this was not reflected in the overall similarity of their genomes. [TOP OF PAGE]

  238. Dynamics of a lytic virus infecting the photosynthetic marine picoflagellate Micromonas pusilla. Cottrell,M.T., Suttle,C.A. (1995). Limnol. Oceanogr. 40:730-739. The impact of Micromonas pusilla virus (MpV) on Micromonas pusilla was inferred from measurements of the abundance of MpV, the kinetics of MpV adsorption to host cells, and the estimated in situ decay rate of MpV infectivity. The viral production rate was calculated to balance the estimated in situ decay rate of MpV infectivity. In inshore water of the Texas coast, the abundance of infective MpV was high and decreased from 130,000/ml in January 1993 to 2100/ml, at the end of April 1993. Decay rates of MpV infectivity in seawater incubated in the dark ranged from 0.06/d at 4 degree C to 0.09/d at 25 degree C. In unattenuated sunlight, decay rates of infectivity were much higher, ranging from 6.9 to 7.1/d. Sunlight-mediated decay rate of viral infectivity was depths-dependent, with an attenuation coefficient estimated to equal 0.73/m. The MpV production rate was 0.79/d, equal to a turnover time of 1.3 d. MpV abundance changed slowly relative to its turnover time, suggesting a stable coexistence of M. pusilla and the lytic virus. The adsorption coefficient for MpV-SP1 and host strain Plymouth 27 was 1.40 x 10-9 ml/min. Using this coefficient, we calculated that from 2 to 10% of the M. pusilla population was lysed per day (avg, 4.4%/d). These results suggest that lysis of phytoplankton by viruses is a process that needs to be incorporated into models of nutrient and energy cycling in aquatic food webs. [TOP OF PAGE]

  239. Spatial and temporal distribution of fecal coliforms, coliphages, moulds and yeasts in freshwater at the semi-arid tropic northeast region in Brazil (Paraiba State). De Ceballos,B.S.O., De Lima,E.O., Koenig,A., Martins,M.T. (1995). Revista de Microbiologia 26:90-100. The distribution of fecal coliforms, coliphages, moulds and yeasts was evaluated during the dry (summer) and rainy (winter) seasons in three lakes and two streams presenting different levels of fecal pollution, located in a semi-arid region of the Northeast of Brazil (Paraiba state). Boqueirao lake waters were found to be suitable for bathing but not for unrestricted irrigation. Rain contributed to fecal pollution to a large extent. Fungal diversity in the lakes increased in parallel with fecal contamination. Moulds were present in all the samples but yeasts were consistently present in the high fecal pollution environments (chi-2o = 69; chi-2cr = 9.21; alpha=0.01), where Candida exhibited the highest diversity (7 species). The incidence of NSF, Candida spp. and C. albicans was higher in the more polluted waters, showing statistically significant differences (NSF-chi-2o = 26.2; Candida spp. chi-2o = 12.96; chi-2cr = 9.21; alpha = 0.01). Both streams did not present any significant differences in the number of taxa and fecal concentrations. However, the incidence of NSF and C. albicans was associated with fecal coliform levels. The results suggested that NSF, Candida spp. and C. albicans are potential indicators of fecal contamination in tropical semi-arid freshwaters. Regional studies on substrate diversity could lead to a better understanding of the distribution and richness of geofungi. [TOP OF PAGE]

  240. Behavior of Escherichia coli and male-specific bacteriophage in environmentally contaminated bivalve molluscs before and after depuration. Dore,W.J., Lees,D.N. (1995). Appl. Environ. Microbiol. 61:2830-2834. We monitored the differential reduction rates and elimination patterns of Escherichia coli and male-specific (F+) bacteriophage during UV depuration for 48 h in oysters (Crassostrea gigas) and mussels (Mytilus edulis) contaminated by short-term (1 to 3 weeks) and long-term (more than 6 months) exposure to sewage in the marine environment. The time taken to reduce levels of E. coli by 90% was 6.5 h or less in all cases. In contrast, the amounts of time needed to reduce levels of F+ bacteriophage by 90% were considerably longer: 47.3 and 41.3 h (after short- and long-term exposures, respectively) in mussels and 54.6 and 60.8 h (after short- and long-term exposures, respectively) in oysters. No differences in the rates of reduction of indicators of viral pollution following exposure of the shellfish to either short- or long-term sewage contamination were observed. Further experiments were conducted with mussels to determine the relative distributions of E. coli and F+ bacteriophage in tissue before and during depuration. Prior to depuration the majority of E. coli organisms (90.1%) and F+ bacteriophage (87.3%) were detected in the digestive tract (i.e., the digestive gland and intestine). E. coli and F+ bacteriophage were reduced in all tissues except the digestive gland to undetectable levels following depuration for 48 h. Within the digestive gland, levels of F+ bacteriophage were reduced to 30% of initial levels, whereas E. coli was reduced to undetectable levels. These results confirm previous laboratory studies showing the differential reductions of levels of E. coli and F+ bacteriophage during depuration. They also demonstrate that these differential elimination patterns are not affected by the duration of sewage contamination and that F+ bacteriophage are retained only in the digestive gland and are not sequestered into other internal tissues. [TOP OF PAGE]

  241. Bacteriophages of Erwinia carotovora and Erwinia ananas isolated from freshwater lakes. Eayre,C.G., Bartz,J.A., Concelmo,D.E. (1995). Plant Dis. 79:801-804. Bacteriophages for Erwinia carotovora subsp. carotovora and for E. ananas were readily isolated from freshwater lakes in Florida and Texas. Approximately 15% of enrichment cultures with 48 strains of E. carotovora yielded phage. Nineteen of 22 phages had distinct host ranges among the 62 strains and up to 10 strains were susceptible to a single phage. Among strains representing 24 serotypes, 12 of 15 phages caused plaques in lawns of 16 serotypes. Each of 13 enrichment cultures with strains of E. ananas yielded at least one phage and five distinct host range patterns emerged among host strains and phage isolates. The number of susceptible hosts for each phage ranged from one to six. [TOP OF PAGE]

  242. Viruses and protists cause similar bacterial mortality in coastal seawater. Fuhrman,J.A., Noble,R.T. (1995). Limnol. Oceanogr. 40:1236-1242. Mesocosms filled with 80 liters of coastal seawater from Santa Monica, California, were used twice (June and November) to budget bacterial production and loss, as well as to assess the relative significance of viral lysis and protist grazing in bacterial mortality. Bacterial abundance was apprx 6 times 10-9 cells liter-1 in June and 2 times 10-9 in November, with viral abundances apprx 2 times 10-10 particles liter-1 in June and 1.5 times 10-10 in November. Incorporation of (3H)thymidine and leucine yielded essentially identical production estimates and allowed calculation of total bacterial mortality in these closed systems. Bacterial growth rates were 1-2 d-1 in June and 1-3 d-1 in November. Three independent lines of evidence indicated that bacterial mortality attributed to grazing by protists was about equal to that attributed to viruses: size fractionation of disappearance of labeled DNA, with a 50% reduction after protists were removed; comparison of protist grazing rates estimated with fluorescently labeled bacteria and virus production-based bacterial lysis rates, with 40-50% of the total ascribed to viruses; and model-based interpretation of the 3.3-4.6% of bacteria visibly infected with assembled intracellular viruses, suggesting that 24-66% of loss is due to infection. Redundant production and loss measurements as well as the independent loss process estimates agreed within apprx 30%, yielding a reasonably balanced budget. We believe the loss of bacteria to viruses reflects a significant dissipation of energy in this ecosystem and that viruses and protists contribute similarly to bacterial mortality. [TOP OF PAGE]

  243. Large double-stranded DNA viruses which cause the lysis of marine heterotrophic nanoflagellates (Bodo sp.) occur in natural marine virus communities. Garza,D.R., Suttle,C.A. (1995). Aquat. Microb. Ecol. 9:203-210. A virus (BV-PW1) which causes lysis of two strains of a marine heterotrophic nanoflagellate belonging to the genus Bodo (strains E1 and E4) was isolated from the coastal waters of Texas. Transmission electron microscopy of ultrathin sections revealed the presence of intracellular virus-like particles 48 h following infection, concomitant with a decline in flagellate numbers. The virus contains double-stranded DNA, is hexagonal in cross-section, ca. 230-300 nm in diameter and contains an electron dense core. It is morphologically similar to virus-like particles which have been observed in other heterotrophic nanoflagellates, and to viruses which have been isolated which infect eukaryotic phytoplankton. Addition of the viruses to cultures of Pseudobodo parvulus (ATCC 50091, formerly Bodo parvulus) or Paraphysomonas imperforata (strain VS1) did not result in lysis. To our knowledge this is the first virus infecting heterotrophic nanoflagellates which has been isolated and maintained in culture. The presence of viruses in seawater which cause lysis of phagotrophic nanoflagellates implies that viruses infect microzooplankton populations in the sea and suggests another important role for viruses in aquatic microbial communities. [TOP OF PAGE]

  244. A study on cyanophages inhibiting the growth of algae producing musty odor. Goto,Y., Kitayama,M. (1995). Water Supply 13:263-266. Recently blue-green algae have grown in large amount in the Lake Biwa. Authors have carried out a study on the cyanophages, which use Phormidium tenue (P. tenue), blue-green alga that produce musty odor in the Lake Biwa, as host and inhibit their growth. The samples used consisted of the surface-layer water in the Lake or the surface running water in Kizu River and Katsura River. A plate culture test by using the double-layered agar method was used in order to detect cyanophages, and the generation of plaque was observed. And, in order to confirm that the cyanophages inhibit the growth of P. tenue, authors also realized a liquid culture test, and observed the growth characteristics of the host. For the plate culture test, three samples presented the formation of plaque. In the liquid culture test, the growth of P. tenue was found to have been inhibited in the three samples. But for all these three samples, P. tenue was not completely killed; therefore, these cyanophages were believed to be temperate phages. By using these cyanophages is expected to be able to inhibit the growth of P. tenue alone without inhibiting the growth of other algae. [TOP OF PAGE]

  245. Direct counts of viruses in natural waters and laboratory cultures by epifluorescence microscopy. Hennes,K.P., Suttle,C.A. (1995). Limnol. Oceanogr. 40:1050-1055. Epifluorescent microscopy was used to determine the abundance of viruses in samples from marine and freshwater environments and in laboratory cultures that were filtered onto 0.02-&micro;m pore-size filters and stained with a cyanine-based dye (Yo-Pro-1). Estimates of viral abundance based on Yo-Pro stained samples were 1.2 to 7.1 times greater than estimates obtained using transmission electron microscopy (TEM). Moreover, the precision of the Yo-Pro based method was much greater than that for TEM (coefficient of variation 7 % versus 20 %, respectively). DNase treatment of samples did not result in lower numbers of particles that could be stained by Yo-Pro, suggesting that the fluorescence was not the result of nucleic acids associated with the surface of particles. These results indicate that the concentration of viruses in natural waters may be higher than previously recognized and imply that the TEM-based method significantly underestimates virus abundance. Virus abundances ranged from 107 to &gt; 108 ml-1 in surface waters along a transect in the western Gulf of Mexico to 109 ml-1 in water overlying a submerged cyanobacterial mat. High counting efficiency, ease of preparation, modest equipment requirements and the possibility of preparing specimens for long-term storage, make the Yo-Pro based method ideal for routine environmental analysis. [TOP OF PAGE]

  246. Significance of bacteriophages for controlling bacterioplankton growth in a mesotrophic lake. Hennes,K.P., Simon,M. (1995). Appl. Environ. Microbiol. 61:333-340. Bacterium-specific viruses have attracted much interest in aquatic microbial ecology because they have been shown to be about 10 times more abundant than planktonic bacteria. So far most of the studies of interactions of planktonic bacteria and viruses have been done in marine environments, and very little is known about these interactions in lakes. Therefore, we studied phage proliferation in Lake Constance, a large mesotrophic lake in Germany. We enumerated bacteria and quantified the fraction of bacteria with mature intracellular phage particles and the number of free viruses by transmission electron microscopy. Between the end of March and early August 1992, peaks of bacterial abundance were followed in 1 to 2 weeks by peaks in the fraction of bacteria containing visible phage particles (0 to 1.7%) and in the number of free viruses (1 times 10-7 to 4 times 10-7 ml-1). We estimated that 1 to 17% +- 12% of all bacteria were phage infected, implying that phage-induced mortality was lt 34% +- 24% of total mortality. A direct comparison between phage-induced mortality, the net decrease of bacterial numbers, and bacterial growth rates indicated that phage-induced mortality accounted for lt 11% of total bacterial mortality during the phytoplankton spring bloom and 18 to 21% following the bloom. Estimated burst sizes ranged from 21 to 121 phages. Phage production rates of 0.5 times 10-6 to 2.5 times 10-6 ml-1 day-1 accounted for 70 to 380% of the observed net increase rates of free phages, implying high rates of simultaneous phage decay. The cyclic dynamics between bacteria and phages and the varying size structure of the intracellular mature phage particles suggested that phage infection was important in structuring the bacterial host assemblage during the study period. [TOP OF PAGE]

  247. Fluorescently labeled virus probes show that natural virus populations can control the structure of marine microbial communities. Hennes,K.P., Suttle,C.A., Chan,A.M. (1995). Appl. Environ. Microbiol. 61:3623-3627. Fluorescently stained viruses were used as probes to label, identify and enumerate specific strains of bacteria and cyanobacteria in mixed microbial assemblages. Several marine virus isolates were fluorescently stained with YOYO-1 or POPO-1 (Molecular Probes, Inc.) and added to seawater samples that contained natural microbial communities. Cells to which the stained viruses adsorbed were easily distinguished from non-host cells; typically, there was undetectable binding of stained viruses to natural microbial assemblages containing &gt;106 bacteria ml-1, but to which host cells were not added. Host cells that were added to natural seawater were quantified with 99 &plusmn; 2 % efficiency using fluorescently labeled virus probes (FLVPs). A marine bacterial isolate (strain PWH3a) was introduced into natural microbial communities that were either supplemented with nutrients or untreated, and changes in the abundance of the isolate were followed using FLVPs. Simultaneously, the concentration of viruses that infected strain PWH3a was monitored by plaque assay. Following the addition of PWH3a, viruses infecting this strain increased from undetectable levels (&lt;1 ml-1 to 2.9 x 107 ml-1 and 8.3 x 108 ml-1 for the untreated and nutrient-enriched samples, respectively. The increase in viruses was associated with a collapse in populations of strain PWH3a from ca. 30% to 2% and 43% to 0.01% of the microbial communities in untreated and nutrient-enriched samples, respectively. These results clearly demonstrate that FLVPs can be used to identify and quantify specific groups of bacteria in mixed microbial communities. As well, the data show that viruses which are present at low abundances in natural aquatic viral communities can control microbial community structure. [TOP OF PAGE]

  248. Viral contribution to dissolved DNA in the marine environment as determined by differential centrifugation and kingdom probing. Jiang,S.C., Paul,J.H. (1995). Appl. Environ. Microbiol. 61:317-325. Dissolved or filterable (<0.2- mu m-pore-size filter) DNA is a ubiquitous component of the dissolved organic matter in the surface waters of this planet. In an effort to understand the composition and possible sources, we subjected dissolved DNA concentrated by vortex flow filtration from offshore and coastal environments to differential centrifugation and probing with 16S rRNA-targeted kingdom oligonucleotide probes. Initial studies with calf thymus soluble DNA and T2 phage particles indicated that high-speed ultracentrifugation (201,000 x g for 90 min), a method to separate viral particles from soluble DNA used by other investigators, resulted in pelleting of nearly all the DNA and virus particles. Lower-speed centrifugation (11,200 to 25,800 x g for 90 min) resulted in >99% of the virus particles being collected in the pellet and similar to 65% of the calf thymus DNA remaining in the supernatant. Employing this approach, we estimate that approximately 50% of the filterable DNA from marine environments is truly soluble or free DNA and that the other half is composed of bound forms (viral particles and, potentially, colloids). Of the bound form, 17 to 30% could be accounted for by viral particles, by calculating the amount of viral DNA on the basis of viral abundance, leaving a portion of the bound form uncharacterized. Kingdom probing with universal, eubacterial, and eucaryotic probes indicated that dissolved DNA hybridized with all of these probes, while purified standard viral DNAs did not, or hybridized only slightly with the universal probe (tailed oligonucleotide only). Collectively, these data indicate that DNA in viral particles is a small component of the dissolved DNA, the majority being of eubacterial and eucaryotic origin. [TOP OF PAGE]

  249. Genetic diversity of related vibriophages isolated from marine environments around Florida and Hawaii, USA. Kellogg,C.A., Rose,J.B., Jiang,S.C., Thurmond,J.M., Paul,J.H. (1995). Mar. Ecol. Prog. Ser. 120:89-98. Although viruses from the marine environment have been enumerated, isolated, and characterized, there is little information on the abundance or global distribution of specific phage types. To this end, we studied the abundance and distribution of phages which infect a marine bacterium isolated from Tampa Bay (Florida, USA), tentatively identified (Microbial ID, Inc., Newark, Delaware, USA) as Vibrio parahaemolyticus. Using this host, we have isolated over 60 phages from the Gulf of Mexico, Tampa Bay, Florida Keys, and Oahu, Hawaii (USA). These isolates are all Myoviridae, with head sizes ranging from 50 +- 0.0 to 65 +- 4.2 nm and tail lengths of 60 +- 3.6 to 100 +- 5.0 rim. The type phage (PHI-16 from Tampa Bay) has a double-stranded DNA genome of 51 to 58 kb. A 1.5 kb EcoRI fragment of this genome has been cloned and used as a gene probe. All of the DNA from the phage isolates hybridized to this probe under stringent conditions, but not to DNA from other marine vibriophages and bacteriophages, suggesting genetic relatedness. Agarose gel electrophoresis of EcoRI digests of the DNAs, followed by Southern transfer and probing with the 1.5 kb gene probe, yielded 6 groups based upon banding patterns. These groups were not segregated geographically within the Florida isolates; however, all of the Hawaiian phages had a common restriction pattern. These data indicate that populations of genetically related phages are widely distributed over large geographic distances in the oceans. [TOP OF PAGE]

  250. Ultrastructural Examination of Virus-like Particles in a Marine Rhizopod (Sarcodina, Protista). Lipscomb,D.L., Riordan,G.P. (1995). Acta Protozoologica 34:35-44. Recent research indicates that bacteriophages are abundant and important for controlling populations in prokaryote microbial communities. The number and role of viruses in eukaryotic microbial communities is less well known. This report demonstrates the presence of polyhedral virus-like particles infecting a free-living, marine rhizopod. The virus-like particle appears to cause cell damage and possibly death. It is able to replicate within the protist and may be able to spread to other members of the population. A survey of the literature indicates that viruses and virus-like particles are present in other protists, perhaps more commonly than usually reported. If viruses are widely dispersed in eukaryote microbial populations, they could contribute significantly to cycling in aquatic food webs and have implications for gene transfer between marine organisms. [TOP OF PAGE]

  251. Complete nucleotide sequence of the gene encoding bacteriophage E endosialidase: implications for K1E endosialidase structure and function. Long,G.S., Bryant,J.M., Taylor,P.W., Luzio,J.P. (1995). Biochem. J. 309 ( Pt 2):543-550. Bacteriophage E specifically recognizes and infects strains of Escherichia coli which display the alpha-2,8-linked polysialic acid K1 capsule. Bacteriophage E endosialidase, which is thought to be responsible for initial absorption of the phage to the host bacterium, was purified, and the N-terminal amino acid sequences of the polypeptide monomer and cyanogen bromide fragments were determined. Synthetic oligonucleotide probes were designed from the N-terminal amino acid sequences and used to identify restriction fragments of bacteriophage E DNA encoding the endosialidase. The primary nucleotide sequence of the bacteriophage E endosialidase gene contains an open reading frame encoding a 90 kDa polypeptide which is processed to give a mature 74 kDa protein. The native enzyme is probably a trimer of identical 74 kDa subunits. In the bacteriophage E genome the K1E endosialidase open reading frame is preceded by a putative upstream promoter region with homology to a bacteriophage SP6 promoter. A central region of 500 amino acids of the deduced protein sequence of the K1E endosialidase was found to have 84% identity to K1F endosialidase. Both endosialidases contain two copies of a sialidase sequence motif common to many bacterial and viral sialidases. These sequences flank the region of greatest identity between the two endosialidase forms, which suggests that this central domain is involved in binding and hydrolysis of the polysialic acid substrate. [TOP OF PAGE]

  252. Viral abundance in aquatic systems: a comparison between marine and fresh waters. Maranger,R., Bird,D.F. (1995). Mar. Ecol. Prog. Ser. 121:1-3. In order to investigate the factors controlling viral abundance, 22 lakes in Quebec were surveyed. We measured viral and bacterial abundance, bacterial production, chlorophyll a, total phosphorus and DOC (dissolved organic carbon) concentrations. Regression models built with these data were compared to models based on literature data, which to date have been collected largely from marine sites. Positive empirical relationships were found between viral abundance and (1) chlorophyll a concentrations, (2) bacterial abundances, (3) bacterial production, and (4) total phosphorus concentration. There was little to no trend in the virus-to-bacteria ratio with increasing trophy. Analysis of covariance revealed significant differences between relations in marine and freshwater systems. The virus-to-bacteria ratio was significantly higher in freshwater (mode = 22.5) than marine environments (mode = 2.5), and there were significantly more bacteria per unit chlorophyll in our freshwater samples. We suggest that this difference is related to the increased dependence of freshwater bacteria on allochthonous material relative to marine systems, as well as the increased relative importance of photosynthetic cyanobacteria in lakes. [TOP OF PAGE]

  253. Viruses of eukaryotic freshwater and marine algae. Meints,R.H., Graves,M.V., Henry,E.C. (1995). p. ??? In Koltin, Y., Leibowitz,M., and Rubio,V. (eds.), Viruses of Fungi and Lower Eukaryotes. [TOP OF PAGE]

  254. [Effect of reproduction of the LPP-3 cyanophage on glutamate dehydrogenase and glutamine synthetase activity in the cyanobacterium Plectonema boryanum]. Mendzhul,M.I., Koltukova,N.V., Lysenko,T.G., Shainskaia,O.A., Perepelitsa,S.I. (1995). Ukr Biokhim Zh 67:33-37. The effect of cyanophage LPP-3 reproduction on glutamate dehydrogenase and glutamine synthetase (GS) in P boryanum cells have been studied. It was determined that the both reactions are intensified by 135% and 220%, accordingly. Isoenzymes of GS were purified from native and infected cell of cyanobacteria. Their physical-and-chemical properties are different. The cyanophage development probably causes specific modification of the cell enzymes. [TOP OF PAGE]

  255. Viral tracer studies indicate contamination of marine waters by sewage disposal practices in Key Largo, Florida. Paul,J.H., Rose,J.B., Brown,J., Shinn,E.A., Miller,S., Farrah,S.R. (1995). Appl. Environ. Microbiol. 61:2230-2234. Domestic wastewater disposal practices in the Florida Keys are primarily limited to on-site disposal systems such as septic tanks, injection wells, and illegal cesspits. Poorly treated sewage is thus released into the highly porous subsurface Key Largo limestone matrix. To investigate the fate and transport of sewage in the subsurface environment and the potential for contamination of marine surface waters, we employed bacteriophages as tracers in a domestic septic system and a simulated injection well in Key Largo, Florida. Transport of bacteriophage PHI-HSIC-1 from the septic tank to adjacent surface canal waters and outstanding marine waters occurred in as little as 11 and 23 h, respectively. Transport of the Salmonella phage PRD1 from the simulated injection well to a canal adjacent to the injection site occurred in 11.2 h. Estimated rates of migration of viral tracers ranged from 0.57 to 24.2 m/h, over 500- fold greater than flow rates measured previously by subsurface flow meters in similar environments. These results suggest that current on-site disposal practices can lead to contamination of the subsurface and surface marine waters in the Keys. [TOP OF PAGE]

  256. Occurrence of fecal indicator bacteria in surface waters and the subsurface aquifer in Key Largo, Florida. Paul,J.H., Rose,J.B., Kellogg,C., Shinn,E.A. (1995). Appl. Environ. Microbiol. 61:2235-2241. Sewage waste disposal facilities in the Florida Keys include septic tanks and individual package plants in place of municipal collection facilities in most locations. In Key Largo, both facilities discharge into the extremely porous Key Largo limestone. To determine whether there was potential contamination of the subsurface aquifer and nearby coastal surface waters by such waste disposal practices, we examined the presence of microbial indicators commonly found in sewage (fecal coliforms, Clostridium perfringens, and enterococci) and aquatic microbial parameters (viral direct counts, bacterial direct counts, chlorophyll a, and marine vibriophage) in injection well effluent, monitoring wells that followed a transect from onshore to offshore, and surface waters above these wells in two separate locations in Key Largo in August 1993 and March 1994. Effluent and waters from onshore shallow monitoring wells (1.8- to 3.7-m depth) contained two or all three of the fecal indicators in all three samples taken, whereas deeper wells (10.7- to 12.2-m depth) at these same sites contained few or none. The presence of fecal indicators was found in two of five nearshore wells (i.e., those that were #1.8 miles [#2.9 km] from shore), whereas offshore wells ($2.1 to 5.7 miles [#3.4 to 9.2 km] from shore) showed little sign of contamination. Indicators were also found in surface waters in a canal in Key Largo and in offshore surface waters in March but not in August. Collectively, these results suggest that fecal contamination of the shallow onshore aquifer, parts of the nearshore aquifer, and certain surface waters has occurred. Current sewage waste disposal practices may have contributed to this contamination. [TOP OF PAGE]

  257. Mycobacteriophage DSGA specific for the Mycobacterium tuberculosis complex. Pearson,R.E., Dickson,J.A., Hamilton,P.T., Little,M.C., Beyer,Jr.W.F. (1995). Becton, Dickinson and Company. 402282(5,476,768). Franklin Lakes, NJ. Mycobacteriophage DS6A has been characterized and found to specifically infect all species of the TB complex, without any detectable infection of mycobacteria species other than those of the TB complex. DNA sequence analysis revealed several potential open reading frames, including one encoding a protein analogous to gp37 of mycobacteriophage L5 and a second encoding a protein with significant homology to the S. coelicolor DNA polymerase b subunit. Based on the DNA sequence analysis, cloning sites can be identified for insertion of reporter genes, making DS6A useful as a reporter phage for specific detection and identification of species of the TB complex. [TOP OF PAGE]

  258. [Alanine dehydrogenase of the cyanobacterium Plectonema boryanum in the early period of cyanophage LPP-3 development]. Perepelitsa,S.I., Koltukova,N.V., Mendzhul,M.I. (1995). Ukr Biokhim Zh 67:47-52. It has been studied how reproduction of LPP-3 in Plectonema boryanum cells influences the alanine dehydrogenase activity. It has been found that immediately after the virus adsorption the enzyme activity falls by 50% and the anabolic reaction is blocked. Physicochemical properties of the enzyme vary as well. An infected cell has one isoenzyme-octamer with pl 9.1-9.2, pH-optimum by action 9-10, molecular weight about 27 kDa. [TOP OF PAGE]

  259. DNA UVB dosimeters. Regan,J.D., Yoshida,H. (1995). J. Photochem. Photobiol. B Biol. 31:57-61. DNA can be used to establish and monitor solar UVB dose. Since the principal molecular site of UVB damage in living organisms is DNA, it is logical to quantitate biologically effective solar UVB in DNA dosimeters. In addition to their particular sensitivity to UVB, DNA dosimeters have the advantages of a 2-pi geometry for collecting diffuse UVB radiation from all vectors, low cost, small size and portability, and no moving parts. Both molecular (cyclobutane pyrimidine dimers) and biological (bacteriophage plaques) dosimeters can be quantitated as endpoints to yield the total dose. DNA dosimeters integrate the absorbed energy of all UVB wavelengths (290-320 nm), are highly sensitive to the differential biological effectiveness of these wavelengths, and also integrate over time in hours, days or weeks of exposure. Our experiments have focused on the demonstration of DNA solar dosimeters in the ocean at various depths, the application of the dosimeters to the terrestrial monitoring of solar UVB under various conditions, and the development of a mini-dosimeter which uses nanograms of DNA and is assayed by polymerase chain reaction. [TOP OF PAGE]

  260. Effects of suspended particulates on the frequency of transduction among Pseudomonas aeruginosa in a freshwater environment. Ripp,S., Miller,R.V. (1995). Appl. Environ. Microbiol. 61:1214-1219. Transduction has been shown to play a significant role in the transfer of plasmid and chromosomal DNA in aquatic ecosystems. Such ecosystems contain a multitude of environmental factors, any one of which may influence the transduction process. It was the purpose of this study to show how one of these factors, particulate matter, affects the frequency of transduction. In situ transduction rates were measured in lake water microcosms containing either high or low concentrations of particulate matter. The microcosms were incubated in a freshwater lake in central Oklahoma. Transduction frequencies were found to be enhanced as much as 100-fold in the presence of particulates. Our results suggest that aggregations of bacteriophages and bacterial cells are stimulated by the presence of these suspended particulates. This aggregation increases the probability of progeny phages and transducing particles finding and infecting new host cells. Consequently, both phage production and transduction frequencies increase in the presence of particulate matter. [TOP OF PAGE]

  261. Characterization of TS-mutants of cyanophage N-1 by their inactivation by physical and chemical agents. Sarma,T.A., Singh,R. (1995). Acta Virol. 39:65-68. The effect of temperature, ultraviolet (UV) light and ethylenediaminetetraacetic acid (EDTA) on the stability of cyanophage N-1, infecting the cyanobacterium Nostoc muscorum was studied. Complete inactivation of the phage occurred at 60 degrees C in 6 mins. All the temperature-sensitive (ts) mutants exhibited faster inactivation at 50 degrees C than the wild type. UV light readily inactivated the particles of the wild giving a survival of 3.44% at a dose of 60 secs. All the ts-mutants were found to be more sensitive to UV light than the wild type. 10(-4) mol/l EDTA inactivated 40% of the wild type in 60 mins. 5 x 10(-4) mol/l EDTA inactivated the wild type nearly completely within 2 mins, while a similar inactivation of ts-mutants required only 90 secs. [TOP OF PAGE]

  262. Presence of large virus-like particles in a eutrophic reservoir. Sommaruga,R., Krössbacher,M., Salvenmoser,W., Catalan,J., Psenner,R. (1995). Aquat. Microb. Ecol. 9:305-330. The presence of large virus-like particles without tail was observed in the water of a severely eutrophied freshwater reservoir. We used transmission electron microscopy (TEM) coupled to a semiautomatic image analysing system to study the size distribution of aquatic viruses. The LVLP had maximum head diameters between 195 and 210 nm. Although the affiliation and host of the LVLP are unknown similarities in size and shape were found with the African swine fever virus. The diffuse organic contamination from piggeries in the catchement area may explain the presence of these LVLP. The overlap in size of the LVLP with the smallest bacteria observed imply serious methodological problems to distinguish these communities under the epifluorescence microscope. Therefore, although at present we do not know how common are LVLP in other aquatic systems we discourage the use of epifluorescence microscopy for viral abundance estimations during routine work. [TOP OF PAGE]

  263. Viruses infecting the marine prymnesiophyte Chrysochromulina spp.: Isolation, preliminary characterization and natural abundance. Suttle,C.A., Chan,A.M. (1995). Mar. Ecol. Prog. Ser. 118:275-282. Sixty-four natural virus communities were concentrated from seawater collected from three locations in Texas' coastal waters (Gulf of Mexico, 27°; 31' N, 96°; 18' W; Aransas Pass 27°; 50' N, 97°; 02' W; Laguna Madre, 27°; 30' N, 97°; 18' W) and screened for the presence of lytic pathogens which infect the marine Prymnesiophyte (Haptophyte) Chrysochromulina brevifilum. Viruses were detected in 16 of the samples and ranged in abundance from 2 to 688 infectious units per liter. The pathogens were detected at the 3 locations, but not on all dates, from December through June when water temperatures were less than 28°;C. A clonal isolate of the virus (CbV-PW1) was obtained by determining the concentration of the infectious agent by a most-probable-number assay and adding 0.2 of an infective unit into each of 20 exponentially growing cultures, removing an aliquot from a culture which lysed and repeating the procedure. The isolate also caused lysis of Chrysochromulina strobilus, but did not lyse 8 other isolates of Chrysochromulina or 5 other genera of Prymnesiophytes that were screened. The double-stranded DNA virus is a polyhedron of about 145-170 nm in diameter with a heavily staining central region that is distinct from the capsid. The appearance of the virions is associated with a granular region in the cytoplasm that does not appear within uninfected cells. Ultimately, viral production results in disruption of the organelles, lysis of the cell and release of the virus particles. Although the number of viruses produced per lytic event is presently unknown we have counted more than 320 virus particles in a single ultrathin section of an infected cell. These results suggest that viruses are likely important in regulating Chrysochromulina populations in the sea and may be the reason that blooms of the genus are relatively rare and ephemeral. [TOP OF PAGE]

  264. Viruses and the microbial loop. Bratbak,G., Thingstad,T.F., Heldal,M. (1994). Microb. Ecol. 28:209-221. The abundance of viral-like particles in marine ecosystems ranges from lt 10-4 ml-1 to gt 10-8 ml-1. Their distribution in time and space parallels that of other biological parameters such as bacterial abundance and chlorophyll a. There is a lack of consensus between methods used to assess viral activity, i.e., rate of change in viral abundance (increase or decrease). The highest rates, 10-100 days-1, are observed in experiments with short sampling intervals (0.2-2 h), while lower rates, on the order of 1 day-1, are observed in experiments with longer sampling intervals (days). Few studies have been carried out, but viruses appear, at least in some cases, to have a significant impact on carbon and nutrient flow in microbial food webs. Viruses have also been demonstrated to exert a species specific control of both bacteria and phytoplankton populations in natural waters. [TOP OF PAGE]

  265. Gene transfer among bacteria under conditions of nutrient depletion in simulated and natural aquatic environments. Goodman,A.E., Marshall,K.C., Hermansson,M. (1994). FEMS Microbiol. Ecol. 15:55-60. Gene transfer among microorganisms has been well demonstrated in laboratory microcosms and in situ, under non-limiting nutrient conditions. The literature contains conflicting opinions, however, as to whether such processes could occur in the absence of nutrients. This review summarises the evidence for the occurrence of gene transfer by conjugation, transformation and transduction among non-growing bacteria in nutrient depleted environments. Conjugation by selftransmissible, or by non-selftransmissible but mobilisable, plasmids has been shown to occur among environmental isolates of Escherichia coli, Enterobacter cloacae, Pseudomonas aeruginosa and marine Vibrio strains. Transduction and transformation have been demonstrated in isolates of P. aeruginosa and marine Vibrio strains, respectively. It is possible that the mechanisms of these processes may be different in non-growing cells in nutrient depleted conditions, compared to those occurring in cells growing in rich media. [TOP OF PAGE]

  266. Virus coagulation in aqueous environments. Grant,S.B. (1994). Environ. Sci. Technol. 28:928-933. A mathematical model is presented for the temporal decline in total infectious units caused by simultaneous first-order inactivation and Brownian coagulation of viruses in an aqueous environment. On the basis of published physicochemical and biological constants for poliovirus, human immunodeficiency virus, and indigenous marine and freshwater bacteriophage, the model predicts that virion-virion coagulation is negligible in most aquatic systems. This analysis provides a framework for investigating the effect of coagulation and inactivation on viral infectivity and for developing more sophisticated models of virus survival outside the host cell. [TOP OF PAGE]

  267. Gene transfer in the marine environment. Hermansson,M., Linberg,C. (1994). FEMS Microbiol. Ecol. 15:47-54. This review summarises the literature on bacterial gene transfer in marine ecosystems. Relevant experiments carried out in model systems are also included. Prerequisites for the main gene transfer mechanisms, transformation, transduction and conjugation are discussed, such as concentrations of extracellular DNA in marine waters, numbers of bacteriophages in sea water and frequency of plasmids in marine bacteria. Transfer of chromosomal genes as well as plasmids are considered. We also discuss the possibility that gene transfer is more frequent in surface- associated bacterial communities. Examples of relevant studies using various solid surfaces and from the air-water interface are summarised. We suggest that there is a higher 'flow-rate' of genetic information through surface-associated communities compared to bulk water communities. [TOP OF PAGE]

  268. Seasonal and diel abundance of viruses and occurrence of lysogeny/bacteriocinogeny in the marine environment. Jiang,S.C., Paul,J.H. (1994). Mar. Ecol. Prog. Ser. 104:163-172. To understand the role of viruses in the marine environment, it is important to know the factors affecting their temporal distribution and the abundance of lysogens. We therefore performed a seasonal and a diel study on viral distribution in Tampa Bay, Florida, USA, and detected the abundance of lysogens and bacteriocinogens amongst marine bacterial isolates from diverse marine environments. We investigated the distribution of viruses, bacterial direct counts, chlorophyll a (chl a), salinity and temperature during a 13 mo period in the Tampa Bay estuary. The results indicated that the viral population had a strong seasonal pattern with the highest concentrations (2.0 +- 0.8 times 10-7) in the summer and lowest (4.8 +- 1.4 times 10-6) in the winter. Viral abundance was negatively correlated with salinity (r = -0.803), and positively correlated with chl a concentration (r = 0.725). A diel study in a seawater mesocosm indicated that viral abundance did not vary on a diel rhythm, but rather peaked after a maximum in bacterial abundance and chl a. Dissolved DNA concentrations displayed diel rhythmicity, suggesting that viruses were not the main source of dissolved DNA. An estimation of the percentage of the bacterial standing stock lysed by viruses based on 4 h intervals ranged from 3.0 to 53.3% per day. Screening bacterial isolates for the presence of inducible prophages indicated that 43% were lysogens or bacteriocinogens, suggesting that lysogeny and bacteriocinogeny are common in the marine environment. [TOP OF PAGE]

  269. Isolation and characterization of V. furnissii phage [Korean]. Ju,J.W. (1994). Journal of the Korean Society for Microbiology 29:685-697. The study of bacteriophage began by F.W. Twort in 1915 and the lytic cycle recognized by d'Herelle in 1917. It repeated about the marine bacteriophage containg Vibrio phage by Smithand Spencers. V. furnissii and V. fluvialis are very close phenotypically. Gas production is the only key differential test in most clinical laboratories. V. furnissii is a new Vibro species which was formerly known as “V. fluvialis biovar II”, “V. fluvialis aero genic”, “V. fluvialis gas+“. The majority of the V. furnissii group isolated from patients with diarrhea and acute gastroenteritis but the role of V. furnissii was not clear. Much resaerch concerning V. furnissii and V. furnissii phage remains unknown. Thus, author isolated two virulent phage from marine products. These 2 phages were examined the ultrastrucrure by electron microscopy and investigated temperature stability, pH stability, inactivation by UV irradiation, antibody production and structural protein analysis. VF phages formed plaques, 2-3mm in diameter, and VF5 formed turbid plaques. VF3 had only head whereas VF5 had tail and head. Although temperature, pH, and UV sensitivity were phage specific, all phages almost inactivated above 70 degree C, and was stable in wide pH range, pH 6.0-pH 10.0 and mostly inactivated by UV irradiation for 100 seconds. Latent period was 60-80 minutes and burst size was 300 PFU/cell in VF3, 400 PFU/cell in VF5. Serologically, antiserum of VF5 neutralized the VF3. Phage DNAs were about 23kb and two all phages were digested with BamHI, Bgl III. Structural protein analysis represented that VF phages have specific structural protein and several common major protein. [TOP OF PAGE]

  270. A New Synechococcus Cyanophage from a Reservoir in Korea. Kim,M., Choi,Y.-K. (1994). Virology 204:338-342. A unicellular cyanobacterium (Synechococcus) and its cyanophage were both isolated from a reservoir in Korea. Although morphologically similar to AS-1, the cyanophage differs from cyanophage AS-1 in some respects. The burst size in the light is approximately 100 plaque-forming units (PFU)/cell. Replication of the virus also occurs in the dark, releasing about 10% of the virus particles observed in the light. Na+ is not necessary for adsorption. [TOP OF PAGE]

  271. Measurements of UV-B radiation in two freshwater lakes: An instrument intercomparison. Kirk,J.T.O., Hargreaves,B.R., Morris,D.P., Coffin,R.B., David,B., Frederickson,D., Karentz,D., Lean,D.R.S., Lesser,M.P. (1994). Ergebnisse der Limnologie/Advances in limnology 43:71-99. Instruments and biological dosimeters were used to measure solar spectral irradiance in two lakes, one clear and the other moderately coloured, with emphasis on the ozone-sensitive UV-B wavelengths. An atmospheric model provided an approximate standard against which were compared commercial instruments from Biospherical Instruments, Inc., International Light, Inc., LI-COR Inc., and Optronic Laboratories, Inc. Comparisons of irradiance in air, and irradiance and attenuation coefficients at several depths, revealed differences in spectral resolution, accuracy, sensitivity to low light energy, and convenience in generating depth-specific profiles. Broadband instruments trade off resolution for simplicity and, in some cases, greater sensitivity, but are subject to errors when the solar spectrum is modified by sun angle, atmospheric column ozone, and the inherent optical properties of the water. For UV-B measurement in lakes, an ideal instrument should have a narrow bandwidth, sensitive and temperature-stable light detector and wavelength filter/selector with high rejection of stray light, well-characterized cosine response and immersion coefficients in both air and water, and an integral sensor for precise measurement of depth. None of the instruments tested matched the ideal, but each had useful characteristics as well as limitations that in some cases could be minimized by coupling their use with an atmospheric model. Analysis of results from bacterial and phage dosimeters using a new “biological attenuation coefficient”, K*, yielded values corresponding to instrument-derived attenuation coefficients in the range of 320-340 nm, suggesting that UV-B and UV-A irradiance contributed to the damaging effects of sunlight. A several-fold reduction in mortality by Mylar super( registered )-screening of dosimeters argues for a significant effect of UV-B light. Bacteria (DNA repair-defective) were consistently more susceptible to light than were phage under matched conditions. [TOP OF PAGE]

  272. [Aspartate kinase complex of Anabaena variabilis during the early period of development of cyanophage A-1]. Koltukova,N.V., Kadyrova,G.K., Lysenko,T.G., Mendzhul,M.I. (1994). Ukr Biokhim Zh 66:41-48. Aspartate kinase activity in cells of A. variabilis has been studied in the dynamics of development of virus infection. An early period of reproduction of cyanophage A-1 has been determined to be conjugated with the increase of biosynthesis of amino acids from aspartate family. Five isoenzymes of aspartate kinase were isolated and purified from A. variabilis cells during early development period of cyanophage A-1. Physicochemical properties and influence of amino acids of aspartate family on the activity of homogeneous isoenzymes have been studied. Retroinhibition effect was not observed in infected cyanobacteria cells, which probably enables one to increase 2-7 times the concentration of amino acids in a cell. Such an increase of the amino acids pool is apparently necessary for realization of viral genome strategy. [TOP OF PAGE]

  273. F-specific bacteria as an indicator of human viruses in natural waters and sewage effluent in northern New Zealand. Lewis,G.D. (1994). Water Sci. Technol. 31:231-234. To assess the F-specific bacteriophage as an indicator of pathogenic viruses, a comparative study has been of the occurrence of F-phage and human enteroviruses in sewage wastes and the marine environment. Although F-phage seemed in several respects to much pathogen behaviour, its low abundance in bathing beach water, uncertainty as to its source and other detection irregularities makes its use as an indicator problematical. [TOP OF PAGE]

  274. Effect of distance from the polluting focus on relative concentrations of Bacteroides fragilis phages and coliphages in mussels. Lucena,F., Lasobras,J., McIntosh,D., Forcadell,M., Jofre,J. (1994). Appl. Environ. Microbiol. 60:2272-2277. Concentrations of fecal bacteria, somatic and F-specific coliphages, and phages infecting Bacteroides fragilis in naturally occurring black mussels (Mytilus edulis) were determined. Mussels were collected over a 7-month period at four sampling sites with different levels of fecal pollution. Concentrations of both fecal bacteria and bacteriophages in mussel meat paralleled the concentration of fecal bacteria in the overlying waters. Mussels bioaccumulated efficiently, although with different efficiencies, all of the microorganisms studied. Ratios comparing the levels of microorganisms in mussels were determined. These ratios changed in mussels collected at the different sites. They suggest that bacteriophages infecting B. fragilis and somatic coliphages have the lowest decay rates among the microorganisms studied, with the exception of Clostridium perfringens. On the contrary, concentrations of F-specific coliphages showed a greater rate of decay than the other bacteriophages at sites more distant from the focus of contamination. Additionally, levels of enteroviruses were studied in number of samples, and in these samples, the B. fragilis bacteriophages clearly outnumbered the enteroviruses The results of this study indicate that, under the environmental conditions studied, the fate of phages infecting B. fragilis released into the marine environment resembles that of human viruses more than any other microorganism examined. [TOP OF PAGE]

  275. Isolation of virus capable of lysing the Brown Tide microalga, Aureococcus anophagefferens. Milligan,K.L.D., Cosper,E.M. (1994). Science 266:805-807. Viruses have been hypothesized to control blooms of Aureococcus anophagefferens gen. et sp. nov. (Chrysophyceae), a marine phytoplankton that since 1985 has caused devastating summer blooms called “brown tide.” By means of ultrafiltration methods, viruses specific to this alga were isolated from both the Great South Bay and Peconic Bay systems of Long Island, New York, during the summer bloom period of 1992. Cell lysis of healthy algal cultures was demonstrated, as well as continuing reinfection with serial transfers of cultures. Electron microscope surveys yielded images of phage-like virus particles with tails that could attach to A. anophagefferens cells within minutes of exposure. The isolation and cultivation of this virus highlights the need for further study of viral infection of eukaryotic algae and the potential for a better understanding of algal bloom control by viral infection. [TOP OF PAGE]

  276. Marine viral ecology: Incorporation of bacteriophage into the microbial planktonic food web paradigm. Murray,A.G., Eldridge,P.M. (1994). J. Plankton. Res. 16:627-641. In the decade since the microbial loop was defined by Azam et al. (Mar. Ecol. Prog. Ser., 59, 1-17, 1983), the importance of the interaction between microbial organisms and the larger planktonic animals has been a subject of controversy. Until recently, grazing was considered to be the major fate of bacterial production. Now, however, viruses are seen to have an important role in microbial processes. We describe how growth and recycling parameters affect the transfer of bacterial production through a microbial loop model that includes viruses. The loop is very inefficient for all reasonable conditions, but its relative importance as a source of mesozooplankton nutrition is variable. The model demonstrates that in mesotrophic coastal waters, the microbial loop is unlikely to supply more than a minor component of mesozooplankton nutrition, a proposition that is supported by accumulating evidence. For oligotrophic pelagic waters, the model indicates that in the absence of viruses the microbial loop, despite its low efficiency, may provide an important resource for mesozooplankton. Bacterial production, without viral mortality, is also relatively important in the case of direct exploitation by salps. Under these conditions, bacteria account for 10-30% of mesozooplankton nutrition. With high levels of bacteriophage activity, zooplankton production is generally reduced by 5-15%. We thus conclude that bacteriophages could significantly affect mesozooplanktonic and, hence, exploitable marine production. [TOP OF PAGE]

  277. Viruses and DNA in marine environments. Paul,J.H., Kellogg,C.A., Jiang,S.C. (1994). pp. 119-128. In In Colwell,R.R., Simidu,U., and Ohwada,K. (eds.), Microbial Diversity in Space and Time. Plenum Press, New York, N.Y. [TOP OF PAGE]

  278. Transduction of a freshwater microbial community by a new Pseudomonas aeruginosa generalized transducing phage, UT1. Ripp,S., Ogunseitan,O., Miller,R.V. (1994). Molecular Ecology 3:121-126. A pseudolysogenic, generalized transducing bacteriophage, UT1, isolated from a natural freshwater habitat, is capable of mediating the transfer of both chromosomal and plasmid DNA between strains of Pseudomonas aeruginosa. Several chromosomal alleles from three different P. aeruginosa strains were found to transduce at frequencies from 10 super(-8) to 10 super(-10) transductants per PFU at multiplicities of infection (MOI) between 0.1 and 1. Transduction frequencies of certain alleles increased up to 1000-fold as MOIs were decreased to 0.01. UT1 is also capable of transducing plasmid DNA to indigenous populations of microorganisms in natural lake-water environments. Data obtained in this study suggest that environmentally endemic bateriophages such as UT1 are formidable transducers of naturally occurring microbial communities. It should be possible to develop model systems to test transduction in freshwater environments using components derived exclusively from these environments. [TOP OF PAGE]

  279. Isolation and characterization of temperature-sensitive mutants of cyanophage N-1. Sarma,T.A., Singh,R. (1994). Acta Virol 38:11-16. Optimal conditions for the induction of temperature-sensitive (ts) mutants of cyanophage N-1 were established after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). A treatment with MNNG (400 micrograms/ml) for 2 hrs at pH 8.0 induced ts-mutants at a maximum frequency of 1.46 x 10(-3). A characterization of 10 such ts-mutants with regard to adsorption, one-step growth and temperature-shift experiments with Nostoc muscorum as host bacterium led to the identification of temperature-sensitive steps in the phage multiplication at the restrictive temperature (37 degrees C). All the mutants were found to be conditionally lethal at 37 degrees C since they resumed growth upon shifting to 28 degrees C. [TOP OF PAGE]

  280. Energetics of cyanophage N-1 multiplication in the diazotrophic cyanobacterium Nostoc muscorum. Singh,S., Bhatnagar,A., Kashyap,A.K. (1994). Microbios 78:259-265. Cyanophage N-1 multiplication was investigated during the latent period of the virus, when super(14)CO sub(2) fixation was inhibited whereas respiratory O sub(2) uptake increased similar to 67% at 4 h after infection. A simultaneous decrease (70%) in the glycogen content of infected cells indicated its catabolic involvement. A chloramphenicol-sensitive rise in glucose-6-phosphate dehydrogenase activity as a result of N-1 infection partly explained the increase in aerobic respiration. The total ATP pool declined to 53% of the control while Ca super(2+)-dependent ATPase activity also declined (25%). In contrast, Mg super(2+)-dependent ATPase activity increased (80%) in comparison with uninfected cells. Results suggest that oxidative phosphorylation was more crucial in the control of cyanophage N-1 development than photophosphorylation under photoautotrophic growth conditions. [TOP OF PAGE]

  281. Isolation of a marine cyanophage infecting the marine unicellular cyanobacterium, Synechococcus sp. NKBG 042902. Sode,K., Oozeki,M., Asakawa,K., Burgess,J.G., Matsunaga,T. (1994). J. Mar. Biotechnol. 1:189-192. A marine cyanophage that infects the marine unicellular cyanobacterium, Synechococcus sp. NKBG 042902, was isolated from seawater. This marine cyanophage possesses a tail with a contractile sheath, which shows two distinct shapes, and is a temperate narrow host range phage that can be induced by mitomycin C. It is distinct from the cyanophage AS-1, which infects the freshwater strain Anacystis nidulans R2, with regard to host range and restriction enzyme pattern, and is designated as mS-1 (marine Synechococcus infecting). [TOP OF PAGE]

  282. Dynamics and distribution of cyanophages and their effect on marine Synechococcus spp. Suttle,C.A., Chan,A.M. (1994). Appl. Environ. Microbiol. 60:3167-3174. Cyanophages infecting marine Synechococcus were frequently very abundant and were found in every seawater sample along a transect in the western Gulf of Mexico, and during a 28 month period in Aransas Pass, Texas. In Aransas Pass their abundance varied seasonally with the lowest concentrations coincident with cooler water and lower salinity. Along the transect, viruses infecting Synechococcus strains DC2 and SYN48 ranged in concentration from a few hundred ml-1 at 97 m depth and 83 km offshore, to ca. 4 x 105 ml-1 near the surface at stations within 18 km of the coast. The highest concentrations occurred at the surface where salinity decreased from ca. 35.5 to 34 ppt and concentrations of Synechococcus were greatest. Viruses infecting strains SNC1, SNC2 and 838BG were distributed in a similar manner, but were much less abundant (&lt; 10 to &gt; 5 x 103 ml-1). When Synechococcus exceeded ca. 103 ml-1, cyanophage concentrations increased markedly (ca. 102 to &gt; 105 ml-1), suggesting that there was a minimum host density required for efficient viral propagation. Data on the decay rate of viral infectivity (d; d-1) as a function of solar radiation (I; mmol quanta m-2 s-1) was used to develop a relationship (d = 0.2610 I - 0.00718; r2 = 0.69) for conservatively estimating the destruction of infectious viruses in the mixed layer of two offshore stations. Assuming that virus production balances losses, and burst size is 250, ca. 5-7 % of Synechococcus would be infected daily by viruses. Calculations based on contact rates between Synechococcus and infectious viruses produce similar results (5-14 %). Moreover, balancing estimates of viral production with contact rates for the most offshore station required that most Synechococcus be susceptible to infection, that most contacts result in infection and that the burst size be about 324 viruses per lytic event. In contrast, in nearshore waters where ca. 80 % of Synechococcus would be contacted daily by infectious cyanophages, only ca. 1 % of the contacts would have to result in infection, in order to balance the estimated virus removal rates. These results indicate that cyanophages are an abundant and dynamic component of marine planktonic communities and are likely responsible for lysing a small but significant portion of the Synechococcus population on a daily basis. [TOP OF PAGE]

  283. The significance of viruses to mortality in aquatic microbial communities. Suttle,C.A. (1994). Microb. Ecol. 28:237-243. A variety of approaches including enumeration of visibly infected microbes, removal of viral particles, decay of viral infectivity and measurements of viral production rates have been used to infer the impact of viruses on microbial mortality. The results are surpisingly consistent and suggest that, on average, about 20 % of marine heterotrophic bacteria are infected by viruses and 10-20 % of the bacterial community is lysed daily, by viruses. The effect of viruses on phytoplankton is less certain, but ca. 3 % of Synechococcus biomass may be lysed daily. The fraction of primary productivity this represents depends upon the relative biomass and growth rate of Synechococcus. Virus enrichment experiments suggest that the productivity of eukaryotic phytoplankton would be ca. 2 % higher in the absence of viruses. Overall, probably about 2-3 % of primary productivity is lost to viral lysis. There is considerable variation about these estimates; however, they represent a starting point for incorporating viral-mediated processes into aquatic ecosystem models. [TOP OF PAGE]

  284. Ecology and characteristics of bdellovibrios from three tropical marine habitats. Sutton,D.C., Besant,P.J. (1994). Mar. Biol. 119:313-320. Marine bdellovibrios have not previously been reported from the southern hemisphere, and knowledge of their occurrence in marine ecosystems is rudimentary. This study examined quantitative and qualitative aspects of bdellovibrios parasitic to the bacterium Vibrio alginolyticus at each of three representative tropical marine habitats of the Great Barrier Reef. Bdellovibrios were found in the water column throughout a 12 mo period from May 1992 at a sandy beach, a mangrove and a fringing coral reef. Their abundance was correlated with water temperature (P lt 0.00 1) and was highest in summer, lowest in winter and intermediate in spring and autumn. Over the sampling period, bdellovibrios were most abundant at the mangrove habitat (36.6 ml-') and least abundant at the reef (9.5 ml-1), but there was substantial variability in numbers at all habitats among seasons and months of the year. On some occasions no bdellovibrios were found in replicate samples from the beach and reef habitats, while on others the maximum detectable by the method used (180 ml-1) was sometimes found at the beach and mangrove habitats. Bdellovibrios within each habitat were uniformly distributed among sampling sites (P gt 0.05). They were more abundant in sub-surface than bottom waters in summer, but the reverse occurred in winter. Midwater samples usually had least bdellovibrios. Bdellovibrio numbers were significantly correlated with those of potential host bacteria colony-forming bacteria at all habitats and total bacteria at the beach and reef habitats. Strain characteristics, primarily based on host range, indicated qualitative differences in bdellovibrio populations among habitats. Pseudomonas atlantica, P. aeruginosa, P. marina, Cytophaga marinoflav, Vibrio gazogenes, V. mimicus and a Spirillum-like bacterium were not parasitised by bdellovibrios from any habitat. Of the other 25 Vibrio spp. tested, most were parasitised by the majority of bdellovibrio strains from each habitat. Strain differences were principally with respect to parasitism of non-Vibrio bacteria. All strains required Na+ and grew at 35 degree C, but some failed to grow at 15 degree C. [TOP OF PAGE]

  285. Frequency, size and distribution of bacteriophages in different marine bacterial morphotypes. Weinbauer,M.G., Peduzzi,P. (1994). Mar. Ecol. Prog. Ser. 108:11-20. The frequencies of cells containing mature phages, the burst sizes, the phage head sizes and the distribution of phages inside cells of different bacterial morphotypes were investigated in the northern Adriatic Sea. Coccoid bacteria more frequently (2.5 %) contained mature phages than rodshaped bacteria (1.2 %) and spirillae [1.4 %). Including an estimation of non-visible infection we found that up to 27 % of rods were infected with viruses, up to 79 % of cocci and up to 100 % of spirillae. The highest overall infection frequency of the entire bacterial community was 30 %. The percentage of rods with mature phages was significantly correlated to increasing rod densities. It is suggested that a threshold density of about 2 x 10 super(5) rods/m exists that is necessary for infection with phages. No threshold densities could be determined for cocci and spirillae. Burst sizes varied strongly between different host morphotypes. The burst sizes of rods increased significantly with the frequency of rods containing mature phages, probably as a result of superinfection of bacteria with phages. [TOP OF PAGE]

  286. Viruses, bacterplankton, and phytoplankton in the southeastern Gulf of Mexico: distribution and contribution to oceanic DNA pools. Boehme,J., et al. (1993). Mar. Ecol. Prog. Ser. 97:1-10. [TOP OF PAGE]

  287. Growth rate and mortality of bacteria in aquatic environments. Boersheim,K.Y. (1993). The University of Trondheim. This thesis consists of two parts. In Part I, I will first discuss the problem of measuring bacterial biomass and production rates, illustrated by studies that I have conducted in a selection of aquatic environments. Thereafter I will discuss consequences of grazing on recycling of organic molecules, to establish a framework for the discussion of the importance of measuring grazing on bacteria. After pointing out grazing as a major causes of bacterial mortality, I will present empirical evidence that bacteriophages also may be very important as factors of bacterial mortality. Part I consists of discussions of methodology, and discussions of my own results compared to data reported in other literature. Part II comprises 10 articles that provide my own background information for Part I. Article I is a study of production rates and biomass of bacteria compared to grazing by cladocerans during one day in a shallow mountain lake on Finse in central Norway. Article II is a one year study of bacterial production and biomass in a humic lake on the west coast of Norway, together with biomass and production rates of phytoplankton and cladoceran zooplankton. Article III is a study of the bacterial production rates and biomass in the Gulf Stream front regions. Article I and II have pertinence for the theme of Chapter 2, bacterial production, but also for Chapter 3, grazing on bacteria. Article IV, V and VI represent basic studies of grazers, and the main experimental effort behind these three articles concentrated on methodological problems. Article IV is a study of grazing rates, and the animal investigated is a common species in eutrophic lakes in temperate climates. In article V we reported a conversion factor between volume and biomass for a protozoan flagellate, and this conversion factors is needed in most modelling efforts concerning grazing, together with estimates of growth yields, as discussed in Chapter 3. Article VI is a methodological study of the use of fluorescent food analogues for measuring grazing rates on bacteria. Fluorescent food analogues have become the major source of information on this process (DBO). [TOP OF PAGE]

  288. Native marine bacteriophages. Børsheim,K.Y. (1993). FEMS Microbiol. Ecol. 102:141-159. [TOP OF PAGE]

  289. Viral mortality of the marine alga Emiliana huxleyi (Haptophyceae) and termination of algal blooms. Bratbak,G., Egge,J.K., Heldal,M. (1993). Mar. Ecol. Prog. Ser. 93:39-48. [TOP OF PAGE]

  290. Spatial distribution of viruses, bacteria and chlorophyll a in neritic, oceanic and estuarine environments. Cochlan,W.P., Wikner,J., Steward,G.F., Smith,D.C., Azam,F. (1993). Mar. Ecol. Prog. Ser. 92:77-87. The spatial distribution of viruses was investigated in the coastal and oceanic waters of the Southern California Bight, USA, and the brackish waters of the Gulf of Bothnia, Sweden, using the direct harvesting technique and transmission electron microscopy. The vertical and horizontal distributions of viruses were examined in relation to bacterial abundance and chlorophyll a. Total virus abundances ranged from 0.3 to 52 times 10-9 l-1; higher concentrations of viruses were found in the upper 50 m of the water column and in coastal environments. Viruses with capsid diameters less than 60 nm dominated the virus community, were morphologically characterized as bacteriophages and were responsible for most of the observed spatial variability. Bacteria abundance alone explained 67% of the spatial variability in virus numbers, thereby suggesting that bacteria constituted the major host organisms for viruses in these physically diverse habitats. [TOP OF PAGE]

  291. Direct electron microscopy study on the morphological diversity of bacteriophage populations in Lake Plußsee. Demuth,J., Neve,H., Witzel,K.-P. (1993). Appl. Environ. Microbiol. 59:3378-3384. Direct electron microscopy of bacteriophages adsorbed to a carbon film without prior enrichment by specific host strains or concentration by physical or chemical methods was used to study the morphological diversity of natural bacteriophage assemblages in a North German lake. All samples contained a mixture of morphologically different tailed viruses, which were regarded as bacteriophages. Most of them had isometric heads and tong noncontractile tails, belonging to morphotype B1 (Siphoviridae). In addition, members of morphotypes A1 (Myoviridae), B2 (Siphoviridae with elongated heads), and C1 (Podoviridae) were present in lower numbers. Only one cubic virus was detected, while no filamentous or pleomorphic phages were found. Up to 11 different phages per sample, and a total of 39 phages when all samples were considered together, could be distinguished by morphological criteria. The total number of phages was estimated to be on the order of 10-8/ml. [TOP OF PAGE]

  292. Inactivation of bacteria and coliphages in highly polluted by secondary effluent and pretreated surface water through UV irradiation at a pilot plant scale. Dizer,H., Bartocha,W., Seidel,K., Lopez,P., Grohmann,A. (1993). Zentralblatt fuer Hygiene und Umweltmedizin 194:490-507. The water of a channel in Berlin which is highly polluted by municipal sewage effluent is treated at the phosphate elimination plant (PEP) Tegel by flocculation and filtration in order to reduce eutrophication in the following Lake Teget. The elimination of bacteria and coliphages in the effluent of the PEP was investigated in a scale pilot UV irradiation reactor installed at the outled of the PEP Tegel. The influence of technical parameters such as flow rate and the arrangement of 23 UV lamps in the reactor on the inactivation was tested. The UV irradiation dose was calculated 119 mJ/cm-2 and 49 mj/cm-2 at a flow rate of 50m-3/h and 120 m-3/h, respectively and for an irradiation zone of 97.5 cm. The colony count of bacteria and concentrations of coliform organisms, E. coli, and feacal streptococci as well as the plaque forming units of coliphages in the influent of the UV reactor were reduced 2-3 lg units by an irradiation dose of 119 mJ/cm-2. These elimination was found being only one lg unit at a UV irradiation dose of 49 mJ/cm-2. The concentration of E. faecalis and Coliphages f2 seeded into the influent of the UV reactor decreased after UV irradiation by 119 mj/cm-2 by 2-4 lg units and 1-2 power of magnitude, respectively. A UV dose of 49 mJ/cm-2 caused only a 90% elimination of E. faecalis and a 75 % inactivation of Coliphages f2. Due to heterogenous distribution and the different retention period of the inflowing water in the irradiation zone, the inactivation of E. faecalis and Coliphages f2 was unequal. Both test organisms decreased in the middle of the reactor up to 2 lg units more than at the sides of the reactor. The hygienic-microbiological quality of a secondary effluent from sewage treatment plants can be improved by a combination of flocculation-filtration and UV irradiation due to their additive elimination effect. However, this UV reactor, which was tested under field conditions can only ensure the inactivation of bacteria and coliphages in the pretreated effluent, if more homogenous distribution of the inflowing water can be achieved. Further, the water must be irradiated by a higher UV dose. [TOP OF PAGE]

  293. Extinction and viruses. Emiliani,C. (1993). Biosystems 31:155-159. The micropaleontological record of deep-sea Sediments is demonstrably continuous through time and, therefore, it can be used to study in detail the evolutionary process. Several taxa, including Coccolithophorida, planktic Foraminifera, Radiolaria, and diatoms, are abundantly represented. Some species, apparently evolved in the marginal marine environment, appear suddenly in the record while other species grade into different ones at rates that range from 100 000 years to millions of years. The rates are usually different for different morphological characters within the same lineage. Every few million years a mass extinction occurs - the disappearance of a number of taxa apparently caused by an environmental upset of some kind. These events are used by stratigraphers to subdivide geologic time. Interspersed between mass extinctions are the background extinctions, the individual extinctions of well-established species while the sympatric species exhibit no sign of stress. It is hypothesized that background extinctions are caused by host-specific viral action. It is further hypothesized that background extinctions are a fundamental component of the process of evolution. [TOP OF PAGE]

  294. Viruses in marine planktonic systems. Fuhrman,J.A., Suttle,C.A. (1993). Oceanography 6:50-62. The last 10-15 years have seen major changes in our views of marine planktonic food webs, primarily from the realization that prokaryotic microorganisms and small eukaryotes are responsible for a significant fraction, often 50% or more, of the primary production and heterotrophic consumption of organic matter in these systems. However, it has only been in the past few years that marine scientists have investigated the roles of viruses in ecological processes. Although this research area is only in its infancy, early results suggest that viruses may be important agents in the mortality or marine microorganisms and in controlling their genetic compositions. This paper will summarize the experiments and measurements that have led to this suggestion as well as the conceptual frame-work within which they are interpreted. [TOP OF PAGE]

  295. Viruses in marine food webs. Fuhrman,J.A., Wilcox,R.M., Noble,R.T., Law,N.C. (1993). pp. 295-298. In In Guerrero,R. and Pedros-Alio,C. (eds.), Trends in microbial ecology. Spanish Society for Microbiology, Barcelona. [TOP OF PAGE]

  296. Grazing by marine nanoflagellates on viruses and virus-sized particles: Ingestion and digestion. González,J.M., Suttle,C.A. (1993). Mar. Ecol. Prog. Ser. 94:1-10. We examined grazing of marine viruses and bacteria by natural assemblages and cultures of phagotrophic nanoflagellates. Ingestion rates were determined using fluorescently-labelled viruses (FLVs) and bacteria (FLB), and 50 or 500 nm-diameter fluorescent microspheres (FMs). Calculated clearance rates of viruses by natural nanoflagellate assemblages were about 4 % of those for bacteria when the bacteria and viruses were present at natural concentrations. Different viruses were ingested at different rates with the smallest virus being ingested at the slowest rate. As well, we found differences in digestion times for the same flagellates grazing on different viruses and for different flagellate assemblages grazing on the same viruses. 50 nm FMs were used as a control for egestion of undigested particles. As rates of digestion were greater than those for ingestion both processes would occur simultaneously; hence, our estimates of grazing rate are likely conservative. Ingestion rates were positively correlated with the concentration of 50 nm FMs. Discrimination against 50 nm FMs in favor of FLVs was also observed. Our calculations suggest that viruses may be of nutritional significance for phagotrophic flagellates. When there are 106 bacteria ml-1 and 107 to 108 viruses ml-1, viruses may represent 0.2-9 % of the carbon, 0.3-14 % of the nitrogen and 0.6-28 % of the phosphorus that the flagellates obtain from ingestion of bacteria. This study demonstrates that both natural assemblages and cultures of phagotrophic nanoflagellates consume and digest a variety of marine viruses, thereby deriving nutritional benefit and serving as a natural sink for marine viral particles. In addition, these results imply that some nanoflagellates are likely capable of consuming a wide spectrum of organic particles in the colloidal size range. [TOP OF PAGE]

  297. Large virus-like particles from vacuoles of phaeodarian radiolarians and from other marine samples. Gowing,M.M. (1993). Mar. Ecol. Prog. Ser. 101:33-43. [TOP OF PAGE]

  298. Comparison of methods for the recovery and quantitation of coliphage and indigenous bacteriophage from marine waters and sediments. Grabow,W.O.K., Reynolds,K.A., Rose,J.B., Giordano,A.T. (1993). pp. 115-117. In In Morris,R.W. and Dufour,A.P. (eds.), HEALTH-RELATED WATER MICROBIOLOGY. PERGAMON PRESS, OXFORD (UK). A variety of anthropogenic influences on marine coastal waters introduces populations of human enteric bacteria and their bacteriophage, some of which may be indicators of municipal waste contamination. This work was undertaken to examine methods for recovery and detection of coliphage in marine waters and sediments. Seeded studies were used to compare viradel and Ultrafiltration methods for the recovery and concentration of both indigenous and introduced viruses from seawater. Ultrafiltration recoveries of MS2 averaged 29.3% in artificial seawater. Viradel methods used to concentrate MD1 coliphage averaged 18.7% recovery when used with natural seawater. A variety of eluants were examined for recovery of phage from sediments. Recoveries ranged from 0.8-100% depending on the type of phage and eluant used. No eluant was capable of providing more efficient recoveries over another, however, indigenous phage 16 was isolated more efficiently than introduced tailed phages T2 and MD1. For phage quantitation, plaque assay counts were compared to particle counts using TEM. TEM counts were usually higher than PFUs in artificial seawater concentrates but lower with eluted marine sediments. Environmental surveys revealed that phage could sometimes be isolated from sediments when they could not be detected in the overlying water column. Preliminary data showed phage could be isolated from sea cucumbers and sponges at higher concentrations than in their surrounding habitats. Therefore, with the development of efficient elution and rapid quantitation techniques, sediments and sea organisms are the most appropriate sampling sites for detection of marine phage populations. [TOP OF PAGE]

  299. F-specific RNA bacteriophages are adequate model organisms for enteric viruses in fresh water. Havelaar,A.H., Olphen,M., Drost,Y.C. (1993). Appl. Environ. Microbiol. 59:2956-2962. Culturable enteroviruses were detected by applying concentration techniques and by inoculating the concentrates on the BGM cell line. Samples were obtained from a wide variety of environments, including raw sewage, secondary effluent, coagulated effluent, chlorinated and UV-irradiated effluents, river water, coagulated river water, and lake water. The virus concentrations varied widely between 0.001 and 570/liter. The same cell line also supported growth of reoviruses, which were abundant in winter (up to 95% of the viruses detected) and scarce in summer (less than 15%). The concentrations of three groups of model organisms in relation to virus concentrations were also studied. The concentrations of bacteria (thermotolerant coliforms and fecal streptococci) were significantly correlated with virus concentrations in river water and coagulated secondary effluent, but were relatively low in disinfected effluents and relatively high in surface water open to nonhuman fecal pollution. The concentrations of F-specific RNA bacteriophages (FRNA phages) were highly correlated with virus concentrations in all environments studied except raw and biologically treated sewage. Numerical relationships were consistent over the whole range of environments; the regression equations for FRNA phages on viruses in river water and lake water were statistically equivalent. These relationships support the possibility that enteric virus concentrations can be predicted from FRNA phage data. [TOP OF PAGE]

  300. Chlorella viruses in diverse freshwaters in Northeast England. Kang,J.Y., Goulder,R., Wollston,C.J. (1993). Lett. Appl. Microbiol. 16:214-216. [TOP OF PAGE]

  301. [The resistance of the DNA of cyanophage LPP-3 to the action of different restriction endonucleases]. Mendzhul,M.I., Syrchin,S.A., Rebentish,B.A., Averkiev,A.A., Busakhina,I.V. (1993). Mikrobiol. Zh. 55:47-53. Data on the study of structure peculiarities of cyanophage LPP-3 DNA are presented in the work. The length of cyanophage DNA calculated by means of the enzymatic hydrolysis by restrictases is 40 +/- 3.5 thou. pairs of bases. Cyanophage LPP-3 DNA was hydrolysed by more than 50 different restrictases. As a result of screening it was found out that the great number of restrictases, which recognized hexanucleotide sequences did not hydrolyze DNA of cyanophage LPP-3. A considerable deviation of the number of the observed sites of restriction from their theoretically expected number for restrictases Hae III and Cfr 131 was established. Restrictases-isoschisomeres with different sensitivity to the methylation of the recognition sites--Msp I, Hpa II and Sau 3A, MboI and DpnI were used to check the availability of methylated bases in LPP-3 DNA. Absence of methylated adenine in the site GATC and methylated cytosine in the second position of the site CCGG were established. The results obtained permit supposing that the expressed counterselection by the sites of recognition of many restriction endonucleases takes place in cyanophage LPP-3 DNA. It is supposed that apparently, this method of protection of its genome in LPP-3 is one of most important but the inconsiderable percentage of site-specific methylation of the virus DNA cannot be completely excluded. [TOP OF PAGE]

  302. Viral dynamics II: A model of the interaction of ultraviolet light and mixing processes on virus survival in seawater. Murray,A.G., Jackson,G.A. (1993). Mar. Ecol. Prog. Ser. 102:105-114. Viruses are an important component in the functioning of marine ecosystems. They are especially vulnerable at the stage when they are free particles seeking a new host. A major factor in viral mortality during this phase is the presence of ultraviolet (UV) radiation. UV radiation penetrates only a short distance into the water column because of a very high attenuation coefficient. Processes that move viruses to the surface change their UV exposure. We have modelled the mortality of viruses subject to UV radiation by means of a Lagrangian Monte-Carlo type model that incorporates viral movements within the mixed layer. For viruses with a given UV-induced surface mortality, mixed-layer depth and UV attenuation coefficient are important factors in their water column mortality. Other more subtle factors can also affect viral mortality: nature of the diurnal thermocline; type of mixing; and the time of day that they are released into the water. Viruses not subject to mixing have their mortality rate enhanced by internal wave motion, although the absolute mortality rates may remain low. Increased UV irradiance associated with atmospheric ozone depletion could significantly change viral mortality in polar environments. UV-induced mortality can be comparable to that from biological factors such as virucidal bacteria. [TOP OF PAGE]

  303. Ch2, a novel halophilic archaeon from an Australian solar saltern. Nuttall,S.D., Dyall-Smith,M.L. (1993). International Journal of Systematic Bacteriology [INT. J. SYST. BACTERIOL. ] 43:729-734. A novel halophilic archaeon, strain Ch2, was isolated from a marine solar saltern in Geelong, Australia. The fact that this organism had a dam-methylated genome suggested that it is closely related to the taxon that includes Halobacterium saccharovorum, Halobacterium sodomense, and Holobacterium trapanicum. A sequence analysis of the 16S rRNA gene (Ch2 has three copies of this gene) showed that Ch2 is phylogenetically equidistant from the genera Haloarcula and Haloferax and closely related to H. saccharovorum. The susceptibility of both Ch2 and H. saccharovorum to the recently isolated halophage HF2 supported the hypothesis that these two organisms are closely related. [TOP OF PAGE]

  304. Distribution of viral abundance in the reef environment of Key Largo, Florida. Paul,J.H., Rose,J.B., Jiang,S.C., Kellogg,C.A., Dickson,L. (1993). Appl. Environ. Microbiol. 59:718-724. The distribution of viral and microbial abundance in the Key Largo, Fla., reef environment was measured. Viral abundance was measured by transmission electron microscope direct counts and plaque titer on specific bacterial hosts in water and sediment samples from Florida Bay (Blackwater Sound) and along a transect from Key Largo to the outer edge of the reef tract in Key Largo Sanctuary. Water column viral direct counts were highest in Blackwater Sound of Florida Bay (1.2 times 10-7 viruses per ml), decreased to the shelf break (1.7 times 10-6 viruses per ml), and were inversely correlated with salinity (r = -0.97). Viral direct counts in sediment samples ranged from 1.35 times 10-8 to 5.3 times 10-8/cm-3 of sediment and average nearly 2 orders of magnitude greater than counts in the water column. Viral direct counts (both sediment and water column measurements) exceeded plaque titers on marine bacterial hosts (Vibrio natriegens and others) by 7 to 8 orders of magnitude. Water column viral abundance did not correlate with bacterial direct counts or chlorophyll a measurements, and sediment viral parameters did not correlate with water column microbial, viral, or salinity data. Coliphage, which are indicators of fecal pollution, were detected in two water column samples and most sediment samples, yet their concentrations were relatively low (2 to 15/liter for water column samples, and lt 2 to 108/cm-3 of sediment). Our findings indicate that viruses are abundant in the Key Largo environment, particularly on the Florida Bay side of Key Largo, and that processes governing their distribution in the water column (i.e., salinity and freshwater input) are independent of those governing their distribution in the sediment environment. [TOP OF PAGE]

  305. Effect of concentrating the virus-rich 2-200 nm size fraction of seawater on the formation of algal flocs (marine snow). Peduzzi,P., Weinbauer,M.G. (1993). Limnol. Oceanogr. 87:105-112. [TOP OF PAGE]

  306. Effect of the submicron size fraction including viruses on the formation of algal flocs (marine snow) in the sea. Peduzzi,P., Weinbauer,M.G. (1993). Limnol. Oceanogr. 38:1562-1565. [TOP OF PAGE]

  307. Calibrating estimates of phage-induced mortality in marine bacteria ultrastructural studies of marine bacteriophage development from one-step growth experiments. Proctor,L.M., Okubo,A., Fuhrman,J.A. (1993). Microb. Ecol. 25:161-182. The timing of lytic phase development and the relationship between host generation times and latent periods were investigated by electron microscopy of one-step growth experiments in two strains of marine Vibrio species. Results were used in a correction factor developed to interpret field studies of phage-infected marine bacteria. Both the number of mature phase per average cell section and the percentage of cells with mature phase increased exponentially by 73-86% into the latent periods. Assuming that bacterial infection and lysis take place continually in the ocean, conversion factors for relating the percentage of visibly infected bacteria to the total percentage of the bacterial community that are phage-infected were calculated as 3.70-7.14. When this range of factors was applied to previously-collected field data Proctor LM, Fuhrman JA (1990) Nature (Lond) 343:60-2; Proctor LM, Fuhrman JA (1991) Mar Ecol Prog Ser 69:133-142 from 3 to 31% of the free-living bacteria and 3 to 26% of particulate-associated bacteria appeared to be phage-infected at any given time. Based upon a steady-state model in which half the daughter cells survive to divide again, the percent of total mortality would be twice the total percentage of phage-infected cells. From 6 to 62% and from 6 to 52% of mortality for the free-living and particulate-associated bacterial community, respectively, may be due to viruses. [TOP OF PAGE]

  308. Viruses and virus-like particles of freshwater and marine eukaryotic algae—a review. Reisser,W. (1993). Arch. Protistenkd. 143:257-265. [TOP OF PAGE]

  309. Spontaneous and induced host range mutants of cyanophage N-1. Sarma,T.A., Kaur,B. (1993). Arch Virol 130:195-200. Optimal conditions for the induction of host-range mutants of cyanophage N-1 by acridine orange were established. Induced host-range mutants were isolated with a frequency of 0.1 to 4.0 x 10(-5) over a spontaneous mutation frequency of 0.2-3.6 x 10(-11). [TOP OF PAGE]

  310. Cyanophages and sunlight: A paradox. Suttle,C.A., Chan,A.M., Chen,F., Garza,D.R. (1993). pp. 303-307. In In Guerrero,R. and Pedros-Alio,C. (eds.), Trends in Microbial Ecology. Spanish Society Microbiology, Barcelona. [TOP OF PAGE]

  311. Marine cyanophages infecting oceanic and coastal strains of Synechococcus: Abundance, morphology, cross-infectivity and growth characteristics. Suttle,C.A., Chan,A.M. (1993). Mar. Ecol. Prog. Ser. 92:99-109. Eight different phycoerythrin- and phycocyanin-containing strains of Synechococcus and one strain of Anacystis were screened against 29 natural virus communities taken from 3 locations in south Texas coastal waters, at different times of the year. In addition, one sample was screened from Peconic Bay, New York. Cyanophages were detected in all samples, but the frequency with which they were detected and their abundance depended upon the strain of Synechococcus that was screened. Viruses that infected red Synechococcus strains were particularly common. In some instances, concentrations infecting a single Synechococcus strain were in excess of 105 ml-1. The abundances of cyanophages were weakly correlated with temperature (r2 = 0.53 to 0.70), although they occurred at all of the temperatures (12-30.4oC) and salinities (18-70 ppt) that were screened. The seven cyanophages that were cloned belonged to the same three families of viruses that have been observed to infect freshwater cyanobacteria, namely the Siphoviridae (formerly Styloviridae), Myoviridae and Podoviridae. The cyanophage clones varied in host-specificity. For example, one clone infected a single Synechococcus strain of 12 that were tested, whereas, another infected 4 of 9 strains tested. Growth characteristics of one of the virus clones was determined for a single host. Photosynthesis in Synechococcus was not affected until near the onset of cell lysis and the virus burst cycle was complete about 17 h post-infection. The burst size was approximately 250 infective particles. The high abundance of cyanophages in the natural environment provides further evidence that viruses are probably important regulators of phytoplankton dynamics in marine systems. [TOP OF PAGE]

  312. Are viruses important partners in pelagic food webs? Thingstad,T.F., Heldal,M., Bratbak,G., Dundas,I. (1993). Trends Ecol. Evol. 8:209-213. Viruses have been assumed to play a rather negligible role as partners in microbial food web dynamics. However, recent discoveries suggest that the rate of virally induced lysis of marine microbial populations may be significant. This, in turn, may have important consequences for the developing conceptual framework of the microbial food web. [TOP OF PAGE]

  313. A rapid luminescent-phage based MPN method for the enumeration of Salmonella typhimurium in environmental samples. Turpin,P.E., Maycroft,K.A., Bedford,J., Rowlands,C.L., Wellington,E.M.H. (1993). Lett. Appl. Microbiol. 16:24-27. Materials such as soils, waters, sewage sludges and foods can contain low numbers of salmonellas. A most-probable-number (MPN) method that utilizes a bioluminescent-bacteriophage is described that allowed the specific determination of as few as one Salmonella typhimurium cell/100 ml of material within 24 h. The method was developed with soil, lake water and sewage sludge inoculated with Salm. typhimurium and had an efficiency of 100% when tested against a traditional MPN method. The protocol is rapid, sensitive, inexpensive, has a lower operator time compared to the traditional MPN method, allows for the repair of injured cells and is amenable to automation. [TOP OF PAGE]

  314. Resistance to co-occurring phages enables marine Synechococcus communities to coexist with cyanophages abundant in seawater. Waterbury,J.B., Valois,F.W. (1993). Appl. Environ. Microbiol. 59:3393-3399. Recent reports documenting very high viral abundances in seawater have led to increased interest in the role of viruses in aquatic environments and a resurgence of the hypothesis that viruses are significant agents of bacterial mortality. Synechococcus spp., small unicellular cyanobacteria that are important primary producers at the base of the marine food web, were used to assess this hypothesis. We isolated a diverse group of Synechococcus phages that at times reach titers of between 10 super(3) and 10 super(4) cyanophages per ml in both inshore and offshore waters. However, despite their diversity and abundance, we present evidence in support of the hypothesis that lytic phages have a negligible effect in regulating the densities of marine Synechococcus populations. Our results indicate that these bacterial communities are dominated by cells resistant to their co-occurring phages and that these viruses are maintained by scavenging on the relatively rare sensitive cells in these communities. [TOP OF PAGE]

  315. Nucleic acids from the host bacterium as a major source of nucleotides for three marine bacteriophages. Wikner,J., Vallino,J.J., Steward,G.F., Smith,D.C., Azam,F. (1993). FEMS Microbiol. Ecol. 12:237-248. The incorporation of 32P-phosphorus into marine bacteriophage nucleic acid was studied in culture experiments to investigate the source of nucleotides used by the phage. We consistently found that the 32P-specific activity in the phage genome increased during the 11 h incubation and was low relative to the specific activity in the medium, averaging 21% (.+-. SD 5.9) for the three phage isolates. This was in accordance with a mathematical model where most of the nucleotides for phage DNA synthesis were derived from the host cell nucleic acid rather than de novo synthesis. We propose that this metabolic strategy may be common among marine phages, as an adaptation to a nutrient poor environment. Consequently, the contribution of free DNA to the dissolved fraction through phage lysis of bacteria, may be less than previously thought. Also during radiolabelling of bacteriophages in natural water samples, isotope dilution may be dependent on the specific growth rate of the bacterial host. [TOP OF PAGE]

  316. Isolation and molecular characterization of five marine cyanophages propagated on Synechococcus sp. strain WH7803. Wilson,W.H., Joint,I.R., Carr,N.G., Mann,N.H. (1993). Appl. Environ. Microbiol. 59:3736-3743. Five marine cyanophages propagated on Synechococcus sp. strain WH7803 were isolated from three different oceanographic provinces during the months of August and September 1992: coastal water from the Sargasso Sea, Bermuda; Woods Hole harbor, Woods Hole, Mass.; and coastal water from the English Channel, off Plymouth Sound, United Kingdom. The five cyanophage isolates were found to belong to two families, Myoviridae and Styloviridae, on the basis of their morphology observed in the transmission electron microscope. DNA purified from each of the cyanophage isolates was restricted with a selection of restriction endonucleases, and three distinguishably different patterns were observed. DNA isolated from Myoviridae isolates from Bermuda and the English Channel had highly related restriction patterns, as did DNA isolated from Styloviridae isolates from Bermuda and the English Channel. DNA isolated from the Myoviridae isolate from Woods Hole had a unique restriction pattern. The genome size for each of the Myoviridae isolates was ca. 80 to 85 kb, and it was ca. 90 to 100 kb for each of the Styloviridae isolates. Southern blotting analysis revealed that there was a limited degree of homology among all cyanophage DNAs probed, but clear differences were observed between cyanophage DNA from the Myoviridae and that from the Styloviridae isolates. Polypeptide analysis revealed a clear difference between Myoviridae and Styloviridae polypeptide profiles, although the major, presumably structural, protein in each case was ca. 53 to 54 kDa. [TOP OF PAGE]

  317. Giant marine viruses? Bratbak,G., Haslund,O.H., Heldal,M., Noess,A., Røeggen,T. (1992). Mar. Ecol. Prog. Ser. 85:201-202. [TOP OF PAGE]

  318. Incorporation of viruses into the budget of microbial C-transfer. A first approach. Bratbak,G., Heldal,M., Thingstad,T.F., Riemann,B., Haslund,O.H. (1992). Mar. Ecol. Prog. Ser. 83:273-280. Viral lysis of bacteria has been suggested to be a quantitatively important process in the removal of bacteria, and potentially also in the production of DOC, in the ocean. In order to investigate the quantitative role of viruses in the pelagic microbial ecosystem, a diel study was undertaken, comprising measurements of particulate and dissolved primary production, bacterial production, bacterial grazing by flagellates, bacterial lysis by viruses, and production of viruses. Estimates of algal excretion (4.7-mu-mol Cl-1 d-1)and bacterial carbon consumption (3.0-mu-mol Cl-1 d-1) estimates by a balance. Predation (2.9-mu-mol Cl-1 d-1) exceeded bacterial production (1.5-mu-mol Cl-1 d-1) estimates by a factor of 2. Major difficulties in balancing the budget emerged however, from the estimates of viral lysis of bacteria (9.2-mu-mol Cl-1 d-1), which exceeded bacterial production by a factor of 6. Despite these problems, results support the idea that viral lysis may be a quantitatively significant process that needs to be incorporated into budgets of microbial C-transfer. [TOP OF PAGE]

  319. Survival and replication of male-specific bacteriophages in molluscan shellfish. Burkhardt,W.I., Watkins,W.D., Rippey,S.R. (1992). Appl. Environ. Microbiol. 58:1371-1373. The survival and replication of male-specific bacteriophages in hard-shelled clams (Mercenaria mercenaria ) and their homogenates were examined to further assess their potential utility as indicator organisms. Trials were conducted in the presence and absence of a suitable bacterial host, Escherichia coli . Results of this study demonstrated that male-specific bacteriophages were unable to replicate in hard-shelled clams, with or without added host cells. In addition, the densities of these bacteriophages were stable for up to 7 days in shellfish held at ambient seawater temperatures (< 25 degree C). Evidence of replication, although not observed in live shellfish, was found to occur in temperature-abused shellfish homogenates and supernatants, but only when a suitable bacterial host was present. [TOP OF PAGE]

  320. Seasonal effects on accumulation of microbial indicator organisms by Mercenaria mercenaria. Burkhardt,W.I., Watkins,W.D., Rippey,C.R. (1992). Appl. Environ. Microbiol. 58:826-831. The ability of hard-shelled clams (Mercenaria mercenaria ) to accumulate fecal coliforms and other microorganisms (Escherichia coli, Clostridium perfringens , and male-specific bacteriophages) was determined over a 1-year period. Twenty separate trials were conducted during different seasons to encompass a wide range of water temperatures. The greatest accumulation of microorganisms in hard-shelled clams occurred during certain periods in the spring, at temperatures ranging from 11.5 to 21.5 degree C. These periods of hyperaccumulation did not always coincide for all organisms; the accumulation of bacteriophages was not predicted by the accumulation of either fecal coliforms or C. perfringens . Bacteriophages and C. perfringens showed significantly higher rates of accumulation than either the fecal coliform group or E. coli , especially during the spring. [TOP OF PAGE]

  321. Depuration rates of northern quahogs, Mercenaria mercenaria (Linnaeus, 1758) and eastern oysters Crassostrea virginica (Gmelin, 1791) in ozone- and ultraviolet light-disinfected seawater systems. Burkhardt,W.I., Rippey,S.R., Watkins,W.D. (1992). J. Shelfish Res. 11:105-109. The relative elimination rates of a diverse group of indicator microorganisms from hard-shelled clams (Mercenaria mercenaria ) and eastern oysters (Crassostrea virginica ) were evaluated in ultraviolet light and ozone-disinfected seawater systems. The indicator organisms included vegetative bacteria (fecal coliforms, Escherichia coli , and enterococci), a spore-forming, anaerobic bacterium (Clostridium perfringens ), and a group of bacterial viruses (male-specific bacteriophages). The addition of ozone to seawater resulted in the rapid inactivation of both the vegetative bacteria and viral indicators. Of the indicators used in this study, C. perfringens was the least affected by ozone. Inactivation and elimination rates, however, were not higher in shellfish placed in ozonated tanks than in shellfish in the ultraviolet light treated control tanks. Bacteriophages were eliminated at a much slower rate than were vegetative or spore-forming bacteria. Regardless of the disinfection system, bacteriophages persisted in depurating shellfish for more than 2 weeks. [TOP OF PAGE]

  322. Bacteriophage typing of Listeria monocytogenes cultures isolated from seafoods. Estela,L.A., Sofos,J.N., Flores,B.B. (1992). J. Food Prot. 55:13-17. Listeria monocytogenes cultures isolated from a variety of seafoods were subjected to phage typing procedures utilizing the French International set of L. monocytogenes bacteriophages. These cultures were also subjected to the activity of newly isolated North American phages to L. monocytogenes . There were 147 serotype is equivalent and 80 serotype 4b L. monocytogenes cultures isolated from 16 varieties of marine products included in this study. L. monocytogenes was most frequently isolated from crab meat, salmon, and shrimp. Bacteriophages to serotype is equivalent isolates most frequently observed as single patterns were 575, 1967, 2685, and 19. Serotype 4b phages observed most frequently were 1317, 2425, and 52 as single phage patterns, and 52/340/110/108/2671/2425/2389 and the new North American phages 90861/910716/93253/90666 as one complete spectrum. The prevalence of L. monocytogenes and their respective phage spectra observed in the 16 varieties of seafoods studied is discussed. [TOP OF PAGE]

  323. The inhibitory effects of the extracts of Zingiber plants on the adsorption, growth, and replication of phage LPP-1 in cyanobacterium. Jido,E.P. (1992). Loyola University of Chicago. [TOP OF PAGE]

  324. Effect of reproduction of cyanophages A-1, S-8K and LPP-3 on proteolysis processes in the cells of cyanobacteria. Mendzhul,M.I., Koltukova,N.V., Lysenko,T.G., Shainskaya,O.A. (1992). Mikrobiol. Zh. 54:90-95. The dynamics of proteolytic activity and formation of protein metabolism products (free aminoacids and peptides) in three virus-cell systems (Anabaena variabilis - A-1, Synechococcus cedrorum-S-8K, Plectonema boryanum - LPP-3) have been studied as affected by cyanophage infection. Proteolytic activity of the cell-free extracts of cyanobacteria is established to considerably change during the cyanophage development. Preparations isolated from the cells 1h after infection are the most active ones. Proteolytic activity of the cells 3h after the infection (period of intensive morphogenesis of virions) is almost commensurable with that of the noninfected cells. The level of proteolytic activity and the content of free aminoacids and peptides well correlate only in the system LPP-3-P. boryanum. Such an agreement was not revealed in two other-virus-cellular systems and this is, probably, connected with different specificity of proteinases, which perform degradation of cell proteins, and with the differences in the processes of the de novo synthesis of amino acids and proteins. Various ways and mechanisms, including proteolysis-performed by virus-induced proteinases, may be involved in formation of a pool of free aminoacids in different virus-cellular systems. [TOP OF PAGE]

  325. Laboratory investigations on the survival of marine bacteriophages in raw and treated seawater. Moebus,K. (1992). Helgol. Meeresunters. 46:251-273. Laboratory investigations were performed to gain insight into the mechanisms which govern the survival bacteriophages in nature. Samples collected in 1988 to 1990 at station “Kabeltonne” near Helgoland were used raw, membrane-filtered (0.15 .mu.m), and/or after inverse filtration through 10 .mu.m-mesh gauze to reduce or increase live and dead particles. The development of natural or artificial bacterial populations and the survival of 2 to 10 distinguishable strains of test phage were followed during incubation at C. The results obtained with most test phages point to the predominant role of indigenous bacteria for marine phage inactivation which was generally enhanced by sample managements leading to improved growth of bacteria. The virucidal properties of the samples differed greatly in total strength as well as in the changes taking place during incubation, the latter resulting in conspicuously differing inactivation curves. Generally, phage inactivation was slow during the first 2 to 3 days of incubation, followed by a peroid of very rapid inactivation which usually coincided with the die-away of colon- forming bacteria. This period lasted either only a few days or until the concentration of test phage was reduced to (near) zero. While the inactivation of most test phage is assumedly caused by proteolytic enzymes released during the die-away of bacteria, the survivability of one test phage (H7/2) was also markedly influenced by the bacteria sensitive to it. Survival rates of the test phages in the laboratory tests were generally of the same order of magnitude as those recently observed with natural phage populations. [TOP OF PAGE]

  326. Further investigations on the concentration of marine bacteriophages in the water around helgoland with reference to the phage-host systems encountered. Moebus,K. (1992). Helgol. Meeresunters. 46:275-292. Between April 3 and September 24, 1991, the concentrations of bacteriophages infecting bacterial strains, isolated in 1990 and during this investigations, were determined in 35 samples of seawater taken at station 'Kabeltonne' adjacent to Helgoland. Similar to the findings of 1990, phage concentrations of several hundred plaque forming units (PFU) ml-1 were observed with a number of indicator strains, the maximum concentration being at least 1.5 .times. 103 PFU ml-1. These high concentrations lasted for only a few days, generally decreasing at rates between 0.6 and 0.9 day-1. Phage concentrations of 0 to 2 PFU ml-1 were found to be prodominant until the end of June, occasionally attaining 5 PFU ml-1. From July through September, when high phage concentrations were observed with some indicator strains, between 0 and 10 PFU ml-1 were found in the majority of tests. As revealed by a final phage-host cross-reaction test, the greater part of 138 indicator bacteria is genetically related, and almost half of the 200 phage strains tested are propagated only by their original indicator bacterium. The possible importance of mutational events for the maintenance of phage-host systems in nature is discussed. [TOP OF PAGE]

  327. Preliminary observations on the concentration of marine bacteriophages in the water around helgoland. Moebus,K. (1992). Helgol. Meeresunters. 45:411-422. In a preliminary survey, conducted between August 28 and October 9, 1990, the concentration of bacteriophages in seawater sampled at intervals of 1 to 4 days near Helgoland (station Kabeltonne) was determined by using indicator bacteria which had been isolated from seawater sampled only some weeks before. With a number of bacterial strains, phage concentrations ranging between 2 and 7 .times. 102 ml-1 were found. However, during the course of this investigation maximal concentrations lasted for a few days only. With most indicator bacteria employed, the concentration of plaque-forming units (PFU) varied in the range of < and 20-30 PFU ml-1. [TOP OF PAGE]

  328. Viral dynamics: A model of the effects of size, shape, motion, and abundance of single-celled planktonic organisms and other particles. Murray,A.G., Jackson,G.A. (1992). Mar. Ecol. Prog. Ser. 89:103-116. The transport of aquatic viruses to particles can be described in terms of diffusive transport from solution. Such transport is influenced by motion of the water relative to the particle. Because transport rate is determined purely by physical factors it is independent of whether the particle is a host or non-host organism. The low viral diffusivity relative to that for dissolved nutrients makes transport enhancement from organism swimming more important for viruses. The virus contact rate with bacteria is relatively unaffected by such motions because of small bacterial sizes. Transport rates for phytoplankton and protozoa can increase over an order of magnitude when swimming motions are considered. Although larger organisms have much higher transport rates per individual, their far lower concentrations in sea water should make small organisms the preferred targets for viruses. Rates of host-virus interactions in culture are closely related to predictions from transport theory. There is a fairly close relationship between bacterial populations and virus disappearance rates in the marine environment, suggesting that non-host organisms are a major cause of viral mortality at the higher ionic strengths typical of sea water. Other factors, such as UV radiation, must also be included when estimating viral mortality in seawater. [TOP OF PAGE]

  329. Application of DNA probes to analysis of bacteriophage distribution patterns in the environment. Ogunseitan,O.A., Sayler,G.S., Miller,R.V. (1992). Appl. Environ. Microbiol. 58:2046-2052. Radiolabeled bacteriophage DNA probes have been used in this study to determine the distribution of Pseudomonas aeruginosa-infecting bacteriophages in natural samples of lake water, sediment, soil, and sewage. The sensitivity of detection of bacteriophage with the DNA probes was between 103 and 104 PFU and 106 to 107 CFU of lysogenized bacteria detectable with a homologous phage DNA probe. Analyses of environmental samples suggest that up to 40% of P. aeruginosa in natural ecosystems contain DNA sequences homologous to phage genomes. By using different bacteriophage DNA probes, the diversity of the bacteriophage population in sewage was estimated to be higher than that in other natural samples. The indication that transducing phages and prophages are widely distributed in the Pseudomonas populations investigated has considerable implications for the frequency of natural gene transfer by transduction and of lysogenic conversion of host bacteria in natural ecosystems. [TOP OF PAGE]

  330. Mortality of marine bacteria in response to enrichments of the virus size fraction from seawater. Proctor,L.M., Fuhrman,J.A. (1992). Mar. Ecol. Prog. Ser. 87:283-293. The potential for viral lysis of marine bacteria in seawater enriched with the virus size fraction from seawater was investigated in seawater samples from Long Island Sound, USA, the eastern Pacific Ocean and the Caribbean Sea. Ultrafiltration was used to concentrate material from seawater in the > 0.05 .mu.m to <0.22 .mu.m size fraction. Electron microscopy counts of virus-like particles in the high molecular weight concentrate (HMWC) correlated closely to epifluorescence microscopy counts of <0.22 .mu.m DAPI-positive, DNase-resistant particles of the HMWC. Acridine orange direct counts of bacterial abundances significantly declined (often to 1/2 or less of controls) when seawater was incubated with 4- to 16-fold enrichnments of HMWC. Microwave treatment of the HMWC before addition to seawater virtually eliminated the declines in bacterial abundance. The combined evidence of the size range of particles, the heat lability of the HMWC and the presence of <0.22 .mu.m DAPI-fluorescent, DNase-resistant particles by epifluorescence microscopy and abundant virus particles by electron microscopy suggests that a dominant bacterial mortality agent in the seawater concentrate was bacteriophage, although we could not rule out an effect of high molecular weight proteins. [TOP OF PAGE]

  331. DNA as a solar dosimeter in the ocean. Regan,J.D., Carrier,W.L., Gucinski,H., Olla,B.L., Yoshida,H., Fujimura,R.K., Wicklund,R.I. (1992). Photochem. Photobiol. 56:35-42. Stratospheric ozone depletion may result in increased solar UV-B radiation to the ocean's upper layers and may cause deleterious effects on marine organisms. The primary UV-B damage induced in biological systems is to DNA. While physical measurements of solar UV-B penetration into the sea have been made, the effective depth and magnitude of actual DNA damage have not been determined. In the experiments reported here, UV-B-induced photoproducts (cyclobutane pyrmidine dimers) have been quantified in DNA molecules exposed to solar UV at the surface and at various depths in clear, tropical marine waters off Lee Stocking Island ( 45' N, 0.7' W), Exuma Cays, Bahamas. 14Cthymidine-labeled DNA or unlabeled bacteriophage .vf.X174 DNA was placed in specially designed quartz tubes at various depths for up to five days. Following exposure, DNA samples were removed to the laboratory where UV-B-induced pyrimidine dimers were quantified using a radiochromatographic assay, and bacteriophage DNA inactivation by solar UV-B was assayed by plaque formation in spheroplasts of Escherichia coli. Pyrimidine dimer induction was linear with time but the accumulation of dimers in DNA with time varied greatly with depth. Attenuation of dimer formation with depth of water was exponential. DNA at 3 m depth had only 17% of the pyrimidine dimers found at the surface. Bacteriophage .vf.X174 DNA, while reduced 96% in plaque-forming ability by a one day exposure to solar UV at the surface of the water, showed no effect on plaque formation after a similar exposure at 3 m. The data collected at the water's surface showed a “surface-enhanced dose” in that DNA damages at the real surface were greater than at the imaginary surface, which was obtained by extrapolating the data at depth to the surface. These results show the sensitivity of both the biochemical (dimers) and biological (phage plaques) DNA dosimeters. DNA dosimeters offer a sensitive, convenient and relatively inexpensive monitoring system, having both biochemical and biological endpoints for monitoring the biologically effective UV-B flux in the marine environment. Unlike physical dosimeters, DNA dosimeters do not have to be adjusted for biological effectiveness since they are sensitive only to DNA- mediated biologically effective UV-B radiation. Results of pyrimidine dimer induction in DNA by soloar UV accurately predicted UV doses to the phage DNA. [TOP OF PAGE]

  332. Estimation of virus production in the sea: II. Field results. Steward,G.F., Wikner,J., Cochlan,W.P., Smith,D.C., Azam,F. (1992). Mar. Microb. Food Webs. 6:79-90. Virus production was estimated in samples from diverse marine environments by incorporation of super(32)P-orthophosphate ( super(32)P sub(i)) into viral DNA. Rates of virus production in the field were found to vary over three orders of magnitude (from < 1 x 10 super(8) to 2.3 x 10 super(11) viruses/l/d). Due to the possibility of intracellular isotope dilution and filtration losses, these rates should be considered minimum estimates. Virus production displayed a strong onshore-offshore gradient which covaried with bacteria abundance and chlorophyll a. Minimum estimates of mortality in two coastal samples (12 and 25% of bacteria production) suggest that viruses were a significant source of bacteria mortality in these environments. The apparent dependence of virus production on host density suggests that significant phage attack is spatially and temporally episodic in the open ocean (e.g. during phytoplankton blooms), but more persistent in the highly productive coastal waters. [TOP OF PAGE]

  333. Estimation of virus production in the sea. I. Method development. Steward,G.F., Wikner,J., Smith,D.C., Cochlan,W.P., Azam,F. (1992). Marine Microbial Food Webs 6:57-78. A method for estimating virus production in seawater was developed and tested in the field. The rates of virus production were determined on the basis of the rate of 32P-orthophosphate (32Pi) or 3H-thymidine (3H-TdR) incorporation specifically into the nucleic acid of the viruses released during the incubation period. The 3H-TdR-incorporation method was designed to specifically detect the production of DNA-containing bacterial viruses. The 32Pi-incorporation method has the potential to measure the production of DNA and RNA viruses of bacteria, algae and protozoa. The 32Pi-incorporation protocols developed in this study, however, measure only the production of DNA viruses. The method provides sensitive detection of virus production with high precision and low blanks. Conversion factors relating label incorporated to viruses produced were derived empirically from culture and field measurements. Due to variable and potentially biased losses of viruses, the accuracy of the method could not be determined in the present study. Virus production measured by this method must be considered minimum estimates at present. This method should be of value in studies of the ecology of viruses in the sea and the roles of viruses in the ocean's biogeochemical dynamics. [TOP OF PAGE]

  334. Marine viruses: Decay rates, diversity and ecological implications. Suttle,C.A., Chen,F., Chan,A.M. (1992). pp. 153-163. In In Nash,C.C., II (ed.), International Marine Biotechnology Conferences “IMBC-91”: Short Communications of Invited Lectures. W. Brown Co., Dubuque. [TOP OF PAGE]

  335. Mechanisms and rates of decay of marine viruses in seawater. Suttle,C.A., Chen,F. (1992). Appl. Environ. Microbiol. 58:3721-3729. Loss rates and loss processes for viruses in coastal seawater from the Gulf of Mexico were estimated using three different marine bacteriophages. Decay rates in the absence of sunlight ranged from 0.009 to 0.028 h-1, with different viruses decaying at different rates. In part, decay was attributed to adsorption by heat-labile particles, as viruses did not decay or decayed very slowly in 0.2-&micro;m-filtered, autoclaved or ultracentrifuged seawater, but continued to decay in cyanide-treated seawater. Cyanide did cause decay rates to decrease, however, indicating that biological processes were also involved. As decay rates were often greatly reduced in 0.8- or 1.0 &micro;m-filtered seawater, whereas bacteria numbers were not, it suggested that most bacteria were not responsible for the decay. Decay rates were also reduced in 3-&micro;m-filtered or cycloheximide-treated seawater, but not in 8-&micro;m-filtered water, implying that flagellates consumed viruses. Viruses added to flagellate cultures decayed at 0.15 h-1, corresponding to 3.3 viruses ingested flagellate-1 h-1. Infectivity was very sensitive to solar radiation and in full sunlight decay rates were 0.4-0.8 -1. Even when UV-B was blocked, rates were as high as 0.17 h-1. Calculations suggest that in clear oceanic waters exposed to full sunlight that most of the viral decay, averaged over a depth of 200 m, would be attributable to solar radiation. In coastal waters, when decay rates were averaged over 24 h and 10 m depth, loss rates of infectivity attributable to sunlight were similar to those resulting from all other processes combined. Consequently, there should be a strong diel signal in the concentration of infectious viruses. In addition, as sunlight destroys infectivity but does not remove virus particles, a large proportion of the viruses in seawater are probably not infective. [TOP OF PAGE]

  336. Daily monitoring of an Adriatic coastal stretch. Volterra,L., Aulicino,F.A., Bonadonna,L., Girolamo,I., LIBERTI,R., Mancini,L., Finarelli,A. (1992). Science of the Total Environment 393-402. An intensive monitoring was carried out during summer along a selected areas of the Adriatic coast, located south of the Po River mouth, Italy. Water samples were examined for microorganisms, chlorophyll a content and salinity. Results showed microbial daily fluctuations related to rains, salinity and algal biomass. Bacteria and phages stratification and tide influence were also observed. [TOP OF PAGE]

  337. Vibrio cholerae phages from open water bodies in the basin of Lake Issyk-Kul and their taxonomy. Arutyunov,Y., Makedonova,L.D., Sayamov,S.R., Kazakbaeva,R.A., Tolmacheva,L.R., Bevz,L.V. (1991). Zhurnal Mikrobiologii 10-13. In the water of open water bodies in the basin of Lake Issyk-Kul the presence of Vibrio cholerae belonging to group O1 and other groups and V. cholerae phages of known serotypes, as well as phages of a new type having no serological and morphological analogs in the current classification of V. cholerae phages, has been established. On the basis of analysis of inaccuracies appearing in the determination of the specificity of V. cholerae phages their systematization within the adequate unified classification of vibriophages is proposed. [TOP OF PAGE]

  338. Significance of several bacteriophage groups as indicators of sewage pollution in marine waters. Cornax,R., Morinigo,M.A., Balebona,M.C., Castro,D., Borrego,J.J. (1991). Water Res. 25:673-678. Seawater samples collected from two beaches with different levels of pollution were studied for the presence of classically and newly proposed fecal indicators such as total and fecal coliforms, fecal streptococci, coliphages, F-specific pahges and bacteriophages of Bacteroides fragilis. Total and fecal coliforms showed lower survival rates in seawater than fecal streptococci, F specific bacteriophages adn coliphages. On the other hand, total coliform concentrations were only higher than those of fecal coliforms in heavily polluted seawater, although in samples with a low level of pollution, fecal streptococci and Escherichia coli C phage counts were generally greater than those showed by fecal coliforms. The low concentration in which F-specific and B. fragilis bacteriophages were detected in marine waters compared to the E. coli bacteriophage levels, is an important shortcoming for the general use of the former microorganisms as universal indicators of fecal pollution. From the results obtained, it may be concluded that fecal streptococci and E. coli C bacteriophages are the most appropriate indicators of the remote pollution in marine waters. [TOP OF PAGE]

  339. Wide-spread occurrence and clonal variation in viruses which cause lysis of a cosmopolitan, eukaryotic marine phytoplankter Micromonas pusilla. Cottrell,M.T., Suttle,C.A. (1991). Mar. Ecol. Prog. Ser. 78:1-9. Seven clonal isolates of viruses which cause lysis of the eukaryotic, naked, photosynthetic flagellate Micromonas pusilla were isolated from the coastal waters of New York, Texas, California and British Columbia, as well as the oligotrophic waters of the central Gulf of Mexico. The viruses are large polyhedrons (ca 115 nm dia.) lacking tails, and are morphologically similar to a previously described virus (MPV) which infected M. pusilla . Restriction fragment analysis of the DNA from these clones using EcoRI revealed unique banding patterns, demonstrating that each of the clones (including 3 that were isolated from the same water sample) were genetically different. Summation of the 17 to 26 visible fragments from the restriction digests, for each of the clones, yielded estimated genomes sizes of 77 to 110 kilobase pairs. In contrast, only 4 different types of viruses could be recognized based on the molecular weights of the major proteins. In field samples the concentrations of viruses causing lysis of M. pusilla were found to be spatially and temporally variable, ranging from &lt; 20 to 4.6 x 10 super(6) infective units/l. [TOP OF PAGE]

  340. Abundance of viruses in marine waters: assessment by epifluorescence and transmission electron microscopy. Hara,S., Terauchi,K., Koike,I. (1991). Appl. Environ. Microbiol. 57:2731-2734. Abundance of bacteria and tiny DNA-associated particles in the upper layer of Japanese coastal and offshore waters was evaluated by epifluorescence microscopy with 0.15-mm-pore-size Nuclepore filters. The number of tiny DNA-associated particles was compared with the abundance of virus particles estimated by transmission electron microscopy. Although a large variation in virus abundance (1.2 x 1011 to 35 x 1011 ml-1) was obtained with the transmission electron microscopy method, the ratio of 4',6-diamidino-2-phylindole-reactive tiny particles to viruses was in a rather narrow range (1.0 to 1.6), indicating that the majority of the tiny DNA-associated particles identified by epifluorescence microscopy were actually virus particles. This result implies the possibility of using epifluorescence microscopy for the evaluation of virus abundance in marine environments. [TOP OF PAGE]

  341. Production and decay of viruses in aquatic environments. Heldal,M., Bratbak,G. (1991). Mar. Ecol. Prog. Ser. 72:205-212. The quantitative significance of aquatic viruses in coastal and in lake water was investigated. The number of viruses in marine surface waters was found to change on a diurnal basis along with changes in number of bacteria and bacterial activity. By inhibiting the production of viruses, we were able to measure viral decay rates up to 1.1 h-1 in marine systems, and up to 0.6 h-1 in a freshwater lake, for the majority of the viral population. A minor fraction (4 to 40%) of the viral population was found to have decay rates lower than 0.05 h-1. The fraction of bacteria containing mature virus particles ranged from 2 to 16%, and the number of viruses released from these bacteria was on average about 50 (range 10 to 300). From these results we estimate that phages may lyse 2 to 24% of the bacterial population per hour. Phages may thus be a major cause of bacterial mortality in aquatic ecosystems and may have a significant impact on the carbon and nutrient flow in aquatic food webs. [TOP OF PAGE]

  342. COLIPHAGES AS ALTERNATE INDICATORS OF FECAL CONTAMINATION IN TROPICAL WATERS. Hernandez-Delgado,E.A., SERRA,M.L., Toranzos,G.A. (1991). Environmental Toxicology and Water Quality 6:131-144. Coliphages as alternate indicators of fecal contamination in tropical waters.Strong evidence has recently been found against the use of the fecal coliforms as indicator organisms of fecal contamination in tropical waters due to their indigenous nature in pristine waters. There is a great need for the development of more rapid, accurate, and low-cost techniques for determining bacteriological water quality. Coliphages seem to be an excellent alternative. We have developed a method to analyze large volumes of pristine water, which we compared to a commonly used direct method. It involves the filtration of water through positively charge filters and a virus-elution step. The eluent is then mixed with culture medium, a host bacterium, and incubated. We sampled pristine tropical rivers, water collected from bromeliads (epiphytic vegetation), sewage-contaminated waters, and marine waters. Concentrations of indicator bacteria were higher than recommended levels for recreational waters, including bromeliad waters. Indicators levels were higher in bromeliad waters than in sewage-contaminated rivers. Phages were isolated only from waters being used for recreational purposes and from sites known to be contaminated with domestic sewage, but not from pristine or bromeliad waters. These results suggest that there is a correlation between the presence of coliphages and fecal contamination. This further suggests that coliphages may be reliable indicators of fecal contamination in the environment. [TOP OF PAGE]

  343. Preliminary observations on the concentration of marine bacteriophages in the water around Helgoland. Moebus,K. (1991). Helgol. Meeresunters. 45:411-422. In a preliminary survey, conducted between August 28 and October 9, 1990, the concentration of bacteriophages in seawater sampled at intervals of 1 to 4 days near Helgoland (station Kabeltonne) was determined by using indicator bacteria which had been isolated from seawater sampled only some weeks before. With a number of bacterial strains, phage concentrations ranging between 2 and 7 x 10 super(2)/ml were found. However, during the course of this investigation maximal concentrations lasted for a few days only. With most indicator bacteria employed, the concentration of plaque-forming units (PFU) varied in the range of < 1 and 20-30 PFU/ml. [TOP OF PAGE]

  344. The effect of cyanophages on the growth and survival of Lyugbya wollei, Anabaenaflos- aquae, and Anabaena circinalis. Monegue,R.L., Phlips,E.J. (1991). J. Aquat. Plant. Manage. 29:88-93. Not sure if following constitutes abstract: Three newly isolated cyanobacteria viruses tested on hHe organisms in laboratory culture experiments. “Cyanophage LW 1 significantly reduced the growth and survival of L. toollei....” Inhibition of growth occurred within 7 days and chlorophyll a concentrations were reduced 95% (relative to controls) within 14 days of inoculahon. (quoted from [TOP OF PAGE]

  345. Concentration of viruses and dissolved DNA from aquatic environments by vortex flow filtration. Paul,J.H., Jiang,S.C., Rose,J.B. (1991). Appl. Environ. Microbiol. 57:2197-2204. Vortex flow filtration (VFF) was used to concentrate viruses and dissolved DNA from freshwater and seawater samples taken in Florida, the Gulf of Mexico, and the Bahamas Bank. Recoveries of T2 phage and calf thymus DNA added to artifical seawater and concentrated by VFF were 72.8 and 80%, respectively. Virus concentrations determined by transmission electron microscopy of VFF-concentrated samples ranged from 3.4 .times. 107/ml for a eutrophic Tampa Bay sample to 2.4 .times. 105 for an oligotrophic oceanic surface sample from the southeastern Gulf of Mexico. Viruslike particles were also observed in a sample taken from a depth of 1,500 m in the subtropical North Atlantic Ocean. Filtration of samples through Nucleopore or Durapore filters (pore size, 0.2 .mu.m) prior to VFF reduced phage counts by an average of two-thirds. Measurements of dissolved-DNA content by Hoechst 33258 fluorescence in environmental samples concentrated by VFF yielded values only ca. 35% of those obtained for samples concentrated by ethanol precipitation (the standard dissolved-DNA method). However, ethanol precipitation of VFF-concentrated extracts resulted in an increase in measurable DNA, reaching 80% of the value obtained by the standard method. These results indicate that a portion of the naturally occurring dissolved DNA is in a form inaccessible to nucleases and Hoechst strain, perhaps bound to protein or other polymeric material, and is released upon ethanol precipitation. Viral DNA contents estimated from viral counts averaged only 3.7% (range, 0.9 to 12.3%) of the total dissolved DNA for samples from freshwater, estuarine, and offshore oligotrophic environments. These results suggest that viruses are not a major component of the dissolved DNA, although they may be involved in its production by lysis of bacterial and phytoplankton cells. [TOP OF PAGE]

  346. Roles of viral infection in organic particle flux. Proctor,L.M., Fuhrman,J.A. (1991). Mar. Ecol. Prog. Ser. 69:133-142. Lack of information on the fate of particulate-associated microorganisms prompted this investigation of viruses (including bacteriophage or phage) and phage-infected cells in sinking particles from sediment traps. Sediment trap material from 30 to 400 m collected from the north Pacific Ocean during the 'VERTEX' cruises in 1980 to 1982 was examined by transmission electron microscopy. Viruses were present in all of the sinking particles examined except for those from one sample, of highly degraded algal cells or small fecal pellets, from 400 m. Viruses in the sinking particles often appeared aggregated. From 0.7 to 3.7% of the bacteria in sinking particles contained mature phage; from these data and limited information from pure cultures, we estimate that 2 to 37% of the particulate-associated bacteria may be killed by viral lysis. Many eukaryotic cells were also apparently infected with viruses, but none (.ltoreq. 50 cells observed) of the cyanobacteria or 'Chlorella-like' cells appeared infected. Viral lysis of bacteria associated with sinking particles and free-living bacteria may be causally linked and may play a role in dissolved organic carbon production and the dynamics of sinking particles. Viral lysis may have major implications for understanding cycling of material and energy in the ocean. [TOP OF PAGE]

  347. Analysis of marine picoplankton community by 16S ribosomal-RNA gene cloning and sequencing. Schmidt,T.M., Delonge,E.F., Pace,N.R. (1991). J. Bacteriol. 173:4371-4378. The phylogenetic diversity of an oligotrophic marine picoplankton community was examined by analyzing the sequences of cloned ribosomal genes. This strategy does not rely on cultivation of the resident microorganisms. Bulk genomic DNA was isolated from picoplankton collected in the north central Pacific Ocean by tangential flow filtration. The mixed-population DNA was fragmented, size fractionated, and cloned into bacteriophage lambda. Thirty-eight clones containing 16S rRNA genes were identified in a screen of 3.2 x 10(4) recombinant phage, and portions of the rRNA gene were amplified by polymerase chain reaction and sequenced. The resulting sequences were used to establish the identities of the picoplankton by comparison with an established data base of rRNA sequences. Fifteen unique eubacterial sequences were obtained, including four from cyanobacteria and eleven from proteobacteria. A single eucaryote related to dinoflagellates was identified; no archaebacterial sequences were detected. The cyanobacterial sequences are all closely related to sequences from cultivated marine Synechococcus strains and with cyanobacterial sequences obtained from the Atlantic Ocean (Sargasso Sea). Several sequences were related to common marine isolates of the gamma-subdivision of proteobacteria. In addition to sequences closely related to those of described bacteria, sequences were obtained from two phylogenetic groups of organisms that are not closely related to any known rRNA sequences from cultivated organisms. Both of these novel phylogenetic clusters are proteobacteria, one group within the alpha-subdivision and the other distinct from known proteobacterial subdivisions. The rRNA sequences of the alpha-related group are nearly identical to those of some Sargasso Sea picoplankton, suggesting a global distribution of these organisms. [TOP OF PAGE]

  348. Promoter recognition by the RNA polymerase from vegetative cells of the cyanobacterium Anabaena 7120. Schneider,G.J., Lang,J.D., Haselkorn,R. (1991). Gene 105:51-60. The transcription start points (tsp) of seven genes of Anabaena 7120 were previously identified by S1 nuclease protection and primer extension experiments using RNA extracted from cells. In the present work, these tsp were confirmed, with one exception, by in vitro transcription using purified RNA polymerases of Anabaena 7120 and Escherichia coli, and crude extracts of Anabaena 7120 active in transcription. In all cases, the template for transcription consisted of closed circular plasmid DNA in which the putative promoter-containing fragment was cloned in front of a strong terminator, which resulted in defined 'pseudo-runoff' transcripts whose sizes correspond (with one exception) to those expected on the basis of the tsp determined for in vivo RNA. These results, together with others obtained with templates containing bacteriophage T4 or cyanophage N1 promoters, led to the conclusion that the principal Anabaena 7120 RNA polymerase prefers promoters whose sequence and spacing approximate that of the E. coli consensus promoter, and that the Anabaena 7120 genes expressed in vegetative cells, characterized to date, have relatively weak promoters. [TOP OF PAGE]

  349. Use of ultrafiltration to isolate viruses from seawater which are pathogens to marine phytoplankton. Suttle,C.A., Chan,A.M., Cottrell,M.T. (1991). Appl. Environ. Microbiol. 57:721-726. Viruses may be major structuring elements of phytoplankton communities, and hence important regulators of nutrient and energy flux in aquatic environments. In order to ascertain if viruses are potentially important in dictating phytoplankton community structure, it is essential to determine the extent to which representative phytoplankton taxa are susceptible to viral infection. We used a spiral ultrafiltration cartridge (30,000 MW cutoff) to concentrate viruses from seawater at efficiencies approaching 100 %. Natural virus communities were concentrated from stations in the Gulf of Mexico, a barrier island pass and a hypersaline lagoon (Laguna Madre), and added to cultures of potential phytoplankton hosts. By following changes in in-vivo fluorescence over time it was possible to isolate several viruses that were pathogens to a variety of marine phytoplankton, including a prasinophyte (Micromonas pusilla), a pennate diatom (likely Navicula sp.), a centric diatom (of unknown taxa), and a chroococcoid cyanobacterium (Synechococcus sp.). As well, we observed changes in fluorescence in cultures of a cryptophyte (Rhodomonas sp.) and a chlorophyte (Nannochloropsis oculata) which were consistent with the presence of viral pathogens. Although pathogens were isolated from all stations, all the pathogens were not isolated from every station. Filterability studies on the viruses infecting Micromonas and Navicula showed that the viruses were consistently infective after filtration through polycarbonate and glass-fiber filters, but were affected by most other filter types. Establishment of phytoplankton/pathogen systems will be important in elucidating the affect that viruses have on primary producers in aquatic systems. [TOP OF PAGE]

  350. Viruses and virus-like particles of eukaryotic algae. van Etten,J.L., Lane,L.C., Meints,R.H. (1991). Microbiol. Rev. 44:586-620. Until recently there was little interest or information on viruses and viruslike particles of eukaryotic algae. However, this situation is changing. In the past decade many large double-stranded DNA-containing viruses that infect two culturable, unicellular, eukaryotic green algae have been discovered. These viruses can be produced in large quantities, assayed by plaque formation, and analyzed by standard bacteriophage techniques. The viruses are structurally similar to animal iridoviruses, their genomes are similar to but larger (greater than 300 kbp) than that of poxviruses, and their infection process resembles that of bacteriophages. Some of the viruses have DNAs with low levels of methylated bases, whereas others have DNAs with high concentrations of 5-methylcytosine and N6-methyladenine. Virus-encoded DNA methyltransferases are associated with the methylation and are accompanied by virus-encoded DNA site-specific (restriction) endonucleases. Some of these enzymes have sequence specificities identical to those of known bacterial enzymes, and others have previously unrecognized specificities. A separate rod-shaped RNA-containing algal virus has structural and nucleotide sequence affinities to higher plant viruses. Quite recently, viruses have been associated with rapid changes in marine algal populations. In the next decade we envision the discovery of new algal viruses, clarification of their role in various ecosystems, discovery of commercially useful genes in these viruses, and exploitation of algal virus genetic elements in plant and algal biotechnology. [TOP OF PAGE]

  351. Circular dichroism studies of salt- and alcohol- induced conformational changes in cyanophage S-2L DNA which contains amino 2 adenine instead of adenine. Vorlickova,M., Hejtmankova,I., Kypr,J. (1991). J Biomol Struct Dyn 9:81-85. DNA molecules containing AT pairs exhibit cesium cation specific conformational behavior. This specificity is shown to be cancelled with the title DNA, which not only concerns its conformational alterations in high-salt aqueous solutions but also the B-to-A transition induced by ethanol. S-2L DNA easily adopts the A-conformation in the presence of millimolar concentrations of CsCl which completely destabilize the A-conformation in calf thymus DNA. The present results demonstrate that the specific effects of cesium cations on DNA are connected with their binding to the AT pairs in the DNA minor groove. [TOP OF PAGE]

  352. THE COMPARATIVE STUDY OF THE LEVELS OF VIRUSES AND INDICATOR BACTERIA IN SOURCE WATER AND TAP WATER. Zhang,C.-Y., Wang,Z.-Q. (1991). Virologica Sinica 6:65-70. The comparative study of the levels of viruses and indicator bacteria in source water and tap water.The presence of any pathogenic viruses in tap water has always been considered a potential public health concern. This study reports the presence levels of viruses and indicator bacteria in the water body of East Lake and treated tap water. During a year's work, indicator bacteria and viral analysis were performed on each sample. We found that total plate count is 2 .times. 103-6.8 .times. 108/L, total coliforms is 130-5.5 .times. 104/L, fecal coliforms is 10-960/L, coliphage is 0.35-65 CFU/L, average is 26.48 CFU/L, enteroviruses is 0-167.5 PFU/L, average is 14.31 PFU/L for the source water of East Lake; we also found that total plate count is 41-500/L, total coliforms is 0-4/L, coliphage is 0-13.6 CFU/L, average is 2.48 CFU/L, enteroviruses is 0-78 PFU/L, average is 6.46 PFU/L for the tap water from the source water of East Lake. Indicator bacteria (standard plate count bacteria, total coliform and fecal coliform), coliphasge and enteroviruses reduction average 97.95-99.99%, 90.63% and 53.18% respectively, for the complete treatment process involving prechlorination, coagulation-sedimentation, sand filtration, and final chlorination. The complete water treatment process was more effective in the reduction of turbitity, coliform, fecal coliform, standard plate count bacteria, and coliphage than enteric viruses. The isolation of human enteric viruses in tap water is not a condemnation of conventional tap water treatment, but an indication that water quality criteria currently accepted to ensure production of microbially safe water do not necessarily ensure the absence of enteric viruses. It is necessary to establish virus standard for tap water, and search for more suitable indicators of the presence of viruses in water. [TOP OF PAGE]

  353. Enumeration and biomass estimation of planktonic bacteria and viruses by transmission electron microscopy. Boersheim,K.Y., Bratbak,G., Heldal,M. (1990). Appl. Environ. Microbiol. 56:352-356. Bacteria and virus particles were harvested from water samples by ultracentrifugation directly onto Formvar-coated electron microscopy grids and counted in a transmission electron microscope. With this technique, the authors have counted and sized bacteria and viruses in marine water samples and during laboratory incubations. By X-ray microanalysis, the authors could determine the elemental composition and dry-matter content of individual bacteria. The dry weight/volume ratio for the bacteria was 600 fg of dry weight mu m super(-3). The potassium content of the bacteria was normal compared with previous estimates from other bacterial assemblages. Virus particles were, by an order of magnitude, more abundant than bacteria in marine coastal waters. During the first 5 to 7 days of incubation, the total number of viruses increased exponentially at a rate of 0.4/day and thereafter declined. The high proliferation rate suggests that viral parasitism may mortality of bacteria in aquatic environments. [TOP OF PAGE]

  354. Control of soft rot Erwinias with bacteriophages [Abstract]. Eayre,C.G., Concelmo,D.E., Bartz,J.A. (1990). Phytopathology 80(10), 994. Bacteriophages of Erwinia carotovora subsp. Carotovora were isolated from lake water by a standard enrichment technique. At least 16 different phages were identified based on host range against 71 strains of soft rot erwinias. One phage caused plaques in lawns of at least one strain of each of the three major soft rot erwinas [sic], e.g., E. c. atroseptica, E. c. carotovora, and E. chrysanthemi. Certain phages infected up to 65% of strains of E. c. carotovora. However, none of the phages caused plaques in lawns of E. herbicola. Bacterial soft rot in slices of potato tubers was prevented when [sic] 12 l of 106 cfu E. c. carotovora/ml. When the concentration of the inoculum was 10-fold greater, some decay occurred, but lesion diameters were reduced by the bacteriophage. [TOP OF PAGE]

  355. Starvation survival of the fish pathogenic bacteria Vibrio anguillarum and Vibrio salmonicida in marine environments. Enger,O., Hoff,K.A., Schei,G.H., Dundas,I. (1990). Microb. Ecol. 74:215-220. The possible fate in sea water of the two fish pathogenic bacteria Vibrio anguillarum and Vibrio salmonicida is discussed on the basis of microcosm experiments with these and other copiotrophic bacteria. Recent articles dealing with the survival of fish pathogens are reviewed, and the reported survival capacities are discussed in relation to ecological mechanisms, such as death, and predation, leading to the removal of bacteria from the water column. [TOP OF PAGE]

  356. Characterization of the bacteriophages infecting marine luminous bacterium Vibrio harveyi (Kaiyosei hakko-saikin Vibrio harveyi ni kansensuru bakuteriofaji no seijo). Hidaka,T., Kobayashi,M., Arimura,S. (1990). Memoirs of the Faculty of Fisheries Kagoshima University 39:159-166. Characterization of bacteriophages infecting marine luminous bacterium Vibrio harveyi.Bacteriophages infecting marine luminous bacterium Vibrio harveyi have been isolated from seawater and fish in Kagoshima Bay [Japan], during 1980 to 1985. The eighty-five of isolated bacteriophages were divided into three groups with their lytic pattern to host bacteria. The representative three V. harveyi-phages were observed about the host range, plaque morphology, particle structure, stability, one step growth characteristics, and serological property. They are phages with a long and noncontractile tail, and also stable phages with double-stranded DNA as genetic material. The test phages varied in host range, plaque morphology, one-step growth characteristics, and serological property. These phages may provide a rapid and sensitive means of differentiating V. harveyi strains by phage typing method. [TOP OF PAGE]

  357. Role of submicrometre particles in the ocean. Isao,K., Hara,S., Terauchi,K., Kogure,K. (1990). Nature 345:242-244. [first paragraph] PARTICULATE matter plays an important part in biogeochemical cycles in the ocean; as particles settle out of the water column, they carry with them carbon and other adsorbed chemicals. Because particles of sub-micrometre size (at the boundary between 'particulate' and 'dissolved' materials) do not have appreciable settling rates in natural waters, they have generally been considered unimportant in the downward flux of particles and the nature and origin of the particles are largely unknown1-5. Here we present results from epifluorescence microscopy and from particle counting which have allowed us to determine the vertical distribution of submicrometre particles (size range 0.38-1 mm). We find that >95% of these particles are non-living and occur in the upper layers of the ocean (50 m) in concentrations of the order of 10 million per millilitre. Many of the non-living particles seem to be fragile and flexible, and seem to have a high water content and to be composed largely of organic material. The size distribution of these submicrometre particles leads us to conclude that a significant portion (at least 10%) of 'dissolved' organic material may in fact be in the form of these small particles, as suggested by Sharp6. [TOP OF PAGE]

  358. Virus-like particles in an ultraoligotrophic lake on Vancouver Island, British Columbia. Klut,M.E., Stockner,J.G. (1990). Canadian Journal of Fisheries and Aquatic Sciences 47:725-730. [TOP OF PAGE]

  359. A new temperate cyanophage NP-1T lysogenizing cyanobacterial cultures belonging to the genera Nostoc and Plectonema. Muradov,M., Cherkasov,G.V., Akhmedova,D.U., Khalmuradov,A.G. (1990). Mikrobiologija (Microbiologiia) 59:1038-1045. A new temperate cyanophage NP-1T growing on Nostoc and Plectonema cyanobacterial cultures is described. Cyanophages of the NP type are widespread in Uzbekistan water basins. The cyanophage has a hexagonal head on a plane with a distance of 78 nm between the facets, but lacks a distinctly differentiated tail. Its adsorption takes 2.5 to 3 h. The lytic cycle takes 30 h with 14 h for the latent period. The phage yield is about 350 particles per infected cell. The DNA has 72 mol.% G + C. The mean contour length is 14.4 .mu.m and the molecular mass of DNA calculated in terms of its length is 28 MDa. When the cyanophage interacts with the host culture, lysogenic clones resistant to the cyanophage appear. [TOP OF PAGE]

  360. Comparative study of NP-IT cyanophages, which lysogenize nitrogen-fixing bacteria of the genera Nostoc and Pleconema (English). Muradov,M.M., Cherkasova,G.V., Akhmedova,D.U., Kamilova,F.D., Mukhamedov,R.S., Abdukarimov,A.A., Khalmuradov,A.G. (1990). Microbiology (translation of Mikrobiologiya) 59:558-563. Comparative characteristics of NP-1T cyanophages causing lysis of nitrogen-fixing Nostoc and Plectonema cultures.The strain specificity of NP-1T cyanophages causing lysis of Nostoc and Plectonema cultures was exerted as differences in the time of formation and in the morphology of plaques. The specificity weas confirmed by the data of restriction analysis using the EcoRV enzyme that hydrolysed the DNA of the cyanophages to yield a different number of fragments. [TOP OF PAGE]

  361. Comparative study of NP-IT cyanophages, which lysogenize nitrogen-fixing bacteria of the genera Nostoc and Pleconema (Russian?). Muradov,M.M., Cherkasova,G.V., Akhmedova,D.U., Kamilova,F.D., Mukhamedov,R.S., Abdukarimov,A.A., Khalmuradov,A.G. (1990). Mikrobiologija (Microbiologiia) 59:819-826. Comparative characteristics of NP-1T cyanophages causing lysis of nitrogen-fixing Nostoc and Plectonema cultures.The strain specificity of NP-1T cyanophages causing lysis of Nostoc and Plectonema cultures was exerted as differences in the time of formation and in the morphology of plaques. The specificity weas confirmed by the data of restriction analysis using the EcoRV enzyme that hydrolysed the DNA of the cyanophages to yield a different number of fragments. [TOP OF PAGE]

  362. Dynamic interactions of Pseudomonas aeruginosa and bacteriophages in lake water. Ogunseitan,O.A., Sayler,G.S., Miller,R.V. (1990). Microb. Ecol. 19:171-186. The persistence and interaction between newly isolated strains of Pseudomonas aeruginosa and resident bacteriophages indigenous to a freshwater environment was monitored over 45 days in lake water microcisms. The interaction between susceptible and resistant bacteria with pure phage (UT1) particles or a mixed phage population (M1) was investigated by following temporal changes in host density, phage-to-bacteria ratio (PBR), and the appearance of apparent prophage carriers within the host population. Decay rates of the phage (UT1) ranged form 0.054 hour- 1 in natural water to 0.027 hour-1 in filtered lake water. About 45% of sensitive bacteria incubated with phase UT1 were pseudolysogenic within 12 hours of incubation in natural lake water. This process was delayed until 72 hours in the sterile lake water control, suggesting that host-phage interaction is promoted in the presence of a viable natural microbial community. Phage UT1 appeared to stabilize the density of host bacteria in lake water at a level of 104 colony-forming units (cfu) ml-1. Bacterial coexistence with the mixed phage (M1) population resulted in an oscillating equilibrium with the pBR stabilizing at about 3. The presence of extraneous homoimmune phages appeared to be detrimental to the stability of the pseudolysogens, which were maintained at a lower population density than prophage-free cells in lake water containing the mixed phage (M1) population. [TOP OF PAGE]

  363. Cyanophages which impact bloom-forming cyanobacteria. Phlips,E.J., Monegue,R.L., Aldridge,F.J. (1990). J. Aquat. Plant. Manage. 28:92-97. Various mesotrophic and eutrophic freshwater environments in the state of Florida were surveyed for the existence of cyanophages. Cyanophages were discovered which infect and kill four common bloom-forming species of cyanobacteria, Lyngbya birgei, Anabaena circinalis, Anabaena flos-aquae , and Microcystis aeruginosa . These cyanophages are being maintained in the laboratory at titers around 10 super(7) PFU/ml. The potential use of these cyanophages to control blooms of these cyanobacteria is discussed. [TOP OF PAGE]

  364. Viral mortality of marine bacteria and cyanobacteria. Proctor,L.M., Fuhrman,J.A. (1990). Nature 343:60-62. Despite the importance of cyanobacteria in global primary productivity and of heterotrophic bacteria in the consumption of organic matter in the sea, the causes of their mortality, particularly the cyanobacteria, are poorly understood. Here the authors report not only high viral abundance in the ocean but also counts of bacteria and cyanobacteria in the final irreversible stage of lytic infection. The latter counts are necessary to evaluate mortality, because the sources, hosts, viability and ages of observed free viruses are unknown; even finding viruses attached to cells does not prove successful infection. Up to 7% of the heterotrophic bacteria and 5% of the cyanobacteria from diverse marine locations contained mature phage; interpretation via culture data indicates that up to 70% of the prokaryotes could be infected. These data demonstrate the existence of a significant new pathway of carbon and nitrogen cycling in marine food webs and have further implications for gene transfer between marine organisms. [TOP OF PAGE]

  365. Bacteriophage-like particles in endocytic bacteria of Cryptomonas (Cryptophyceae). Schnepf,E., Melkonian,M. (1990). Phycologia 29:338-343. A species of Cryptomonas (Cryptophyceae) from the Collection of Algal Cultures at Goettingen was found to contain endocytic bacteria, both confined in peribacterial vacuoles and non-membrane-bound. Some of the latter contained bacteriophage-like particles. Lysed bacteria and bacteriophages were not observed free within the cytoplasm, but occasionally occurred within autolysosome-like vacuoles. Possible methods by which the bacteria/bacteriophage consortium could be maintained are discussed. [TOP OF PAGE]

  366. Infection of phytoplankton by viruses and reduction of primary productivity. Suttle,C.A., Chan,A.M., Cottrell,M.T. (1990). Nature 347:467-469. Natural marine waters contain roughly 106 to 109 virus particles per ml, yet their role in aquatic ecosystems and the organisms that they infect remain largely unknown. Electron microscopy has been used to study interactions between viruses and their hosts, focusing mainly on pathogens to prokaryotic organisms. The authors demonstrate that viral pathogens infect a variety of important marine primary producers, including diatoms, cryptophytes, prasinophytes and chroococcoid cyanobacteria. Also, addition to sea water of particles in the 0.002-0.2 &micro;m size range, concentrated from sea water by ultrafiltration, reduced primary productivity (14C-bicarbonate incorporation) by as much as 78%. Results indicate that in addition to grazing and nutrient limitation, infection by viruses could be a factor regulating phytoplankton community structure and primary productivity in the oceans. [TOP OF PAGE]

  367. AS-1 cyanophage infection inhibits the photosynthetic electron flow of phohtosytem II in Synechococcus sp. PCC 6301, a cyanobacterium. Teklemariam,T.A., Demeter,S., Deak,Z., Suranyi,G., Borbely,G. (1990). FEBS Lett. 270:211-215. In Synechococcus sp. cells AS-I cyanophage infection gradually inhibits the photosystem IImediated photosynthetic electron flow whereas the activity of photosystem I is apparently unaffected by the cyanophage infection. Transient fluorescence induction and flash-induced delayed luminescence decay studies revealed that the inhibition may occur at the level of the secondary acceptor, Q(B) of photosystem II. In addition, the breakdown of D(1)-protein is inhibited, comparable to DCMU-induced protection of D(1)-protein turnover, in AS- I-infected cells. [TOP OF PAGE]

  368. Sequence counter-selection in cyanophage. Bancroft,I., Smith,R.J. (1989). p. 316 In Rogers,L.J. and Gallon,J.R. (eds.), BIOCHEMISTRY OF THE ALGAE AND CYANOBACTERIA. An analysis of the cleavage of native and cloned DNA of five cyanophage which infect Anabaena 7120 by 34 restriction endonucleases provided evidence of sequence counter-selection similar to that present in T sub(7). One group are isoschizomers of Anabaena) 7120 endogenous restriction endonucleases. Another group contain the subsequence GATC; and a third group contain dicytosine residues. The fourth group have no common sequence structure and may represent isoschizomers of restriction endonucleases present in the host range of the five cyanophage. Cyanophages AN-23, AN-13, and A-4L do not tolerate sequence methylation. A-1L and AN-10 tolerate adenine methylation, but differ in their tolerance of cytosine methylation. AN-10 appears able to prevent cytosine methylation by host enzymes. AN-10 and A-1L are closely related. Comparison of their restriction maps shows that counter-selection of some Hae III sites in AN-10 has occurred since divergence of the phage from their common ancestor. [TOP OF PAGE]

  369. FRNA bacteriophages as indicators of fecal pollution in an estuarine environment. Boyd,D.M., Kator,H., Rhodes,M. (1989). J. Shelfish Res. 8:482 A number of alternate microbial indicators of fecal pollution in receiving waters have been proposed. One of these, the male-specific coliphage-containing ribonucleic acid (FRNA), has not been evaluated in shellfish growing waters. The occurrence of FRNA phage in point source impacted water samples may be a better measure of pathogenic viral persistence than traditional coliform indicators. Accordingly, water and sediment samples were obtained from a tidal creek of the Ware River, Virginia, which receives treated effluent from a sewage treatment plant. Samples were assayed for male-specific phage using a method designed to enumerate FRNA phage lytic for Escherichia coli . Samples were collected along a salinity gradient over a 6 month period to evaluate the seasonal and spatial distribution of FRNA phage. Fecal coliform densities and selected physical/chemical parameters were also measured and compared with phage titer and occurrence. These results and the applicability of this assay method as an indicator of water quality in an estuarine watercourse impacted by a point source of sewage pollution are discussed. [TOP OF PAGE]

  370. Inhibitory effect of the extracts of Zingiber species on the adsorption and replication of phage LPP-1 in cyanobacterium. Jido,E.P., Dhaliwal,A.S. (1989). Toronto, Ont. (Canada). Annu. Meet. of the Phycological Soc. of America. 1900.Rhizome extracts from Zingiber officinale and Zingiber zerumbet were prepared by grinding in saline. Cyanobacterium was treated with each of the extracts (20% v/v). Extract treated cyanobacterium were inoculated with phage LPP-1. The extract of Z. officinale caused 59% inhibition of virus adsorption and 77% inhibition of burst size, whereas Z. zerumbet caused 67% inhibition of virus adsorption and 98% inhibition of burst size. [TOP OF PAGE]

  371. Occurence of bacteriophages infectecting Bacteriodes fragilis and other viruses in polluted marine sediments. Jofre,J., Blasi,M., Bosch,A., Lucena,F. (1989). Water Sci. Technol. 21:15-19. Numbers of B. fragilis bacteriophages in comparison to coliphages, enteroviruses and rotaviruses were evaluated by different methods in sediments of a coastal area near Barcelona which received substantial amounts of pollution of domestic origin. Phages infecting B. fragilis should be eluted from sediments prior to their enumeration, in the same way as solid-associated animal viruses. Phages infecting B. fragilis were better eluted by glycine buffer at alkaline pH than by a caotropic agent (beef extract-sodium nitrate). Such differences between glycine buffer and sodium nitrate were not evident when enteroviruses and rotaviruses were eluted from sediments. This suggests that elution with glycine buffer is preferable for bacteriophages, while teh use of caotropic is advisable for animal viruses, because of the simplicity of the methodology. In the studied arte, coliphages were the more abundant viruses. B. fragilis phages outnumbered rotaviruses and enteroviruses bya factor of more than ten. The ratios between phages active against B. fragilis and either enteroviruses or rotaviruses in marine sediments were similar to the ratios found in sewage, thus indicating that they have a similar fate. [TOP OF PAGE]

  372. [Research, education and environmental health related to pollution in the Gulf]. Paoletti,A., Parrella,A., Gargiulo,E., Aliberti,F. (1989). Annali di Igiene 1:495-523. At Italian-Russian International Conference on “Role of the University on ecological education and training,” was illustrate six topics of 30 years of our scientific and didactic activity on Environmental Hygiene, here below summarized: I. At first time, sludges of biological treatment plants and domestic sewage were frequently utilized under bacteriological control as economical and ecological fertilizers of land and waters. At present such a custom is very rare owing the chemical pollution of sewage continuously increasing; but in some countries it is still in use, and is our opinion and experience that organic waste material must be reused as fertilizer of land, more and more devoid of humus and subject to erosion of winds and waters. Some treatment plants are shown, and related plankton pyramid's. II. Pilot sewage treatment plants are frequently used in our experiments and training, for study and control of the biological degradation of organic matter, for evaluate the disappearance rate of bacteria and viruses, for investigate the foric action and behaviour of chemical and radioactive pollutants, for quantify their accumulation in the sludges of sewage treatment plants, and so forth. Different pilot plants are used, located both in our laboratories both in industries; in nuclear power plant are tested at the same time 3 models of 3 different plants (biodiscs, activated sludges, biofiltering channels), working with prevalent algal growth. III. Many species of microorganisms (metazoa, protozoa, algae, fungi, bacteria, viruses and new species like Bdellovibrio) are present in aerobic sewage treatment plants (activated sludge, bacterial bed, biodiscs, lagooning, etc.); in anaerobic treatment (digesters) prevail only methane-producing bacteria. Some of these organisms are very abundant and very active as consumers of organic matter; others are characteristic indicators of well balanced purification or of bad purification owing acute variation of organic load or presence of toxic substances in sewage. Many strains are antibiotic-producing, or Vit. B12 producing; others explain a strong lytic activity or are neuraminidase-formers. Production of great amount of biofloculant polysaccharides useful on sedimentation of organic matter is enhanced by adding particular organic pollutants like distillery wastes and others. Sewage treatment plants are good means for scientific research of particular biota continuously available and for food microbiological training for students and technicians on pathogens present in treated and untreated sewage and in sludges. IV. Big fecal pollution of coastal waters is clearly dangerous because of bathing beaches, shellfish farming, bacterial aerosols, damage to marine biota, eutrofication, aesthetic problems. [TOP OF PAGE]

  373. Evaluation of Salmonella typhimurium WG49 host assay method for enumeration of male-specific coliphages in an estuarine environment. Rhodes,M.W., Kator,H. (1989). J. Shelfish Res. 8:481 An assay method for enumeration of male-specific coliphages in sewage was evaluated in a Virginia subestuary subject to nonpoint pollution sources including fecal inputs from livestock. Phages were enumerated using the bacterial host Salmonella typhimurium WG49 modified to produce Escherichia coli sex pili. WG49 has been reported to detect male-specific ribonucleic acid (FRNA) coliphages in sewage with little interference from somatic salmonella phages. FRNA phages and fecal coliforms were enumerated from water and sediment samples collected seasonally from the estuary and feeder streams and microbiological densities related to selected environmental parameters. Examination of 300 purified phage isolates showed 99% were RNAase resistant, 97% were lytic on the female parent salmonella strain (WG45), 4% were lytic on male E. coli and none were lytic on female E. coli . Parallel enumeration of samples on WG45 and WG49 yielded equal or greater phage densities on the former host. The significance of somatic phage recovery by the S. typhimurium WG49 host in an estuary lacking a point source of sewage is discussed. [TOP OF PAGE]

  374. An analysis of restriction endonuclease sites in cyanophages infecting the heterocystous cyanobacteria Anabaena and Nostoc. Bancroft,I., Smith,R.J. (1988). J Gen Virol 69 ( Pt 3):739-743. An analysis of restriction endonuclease cleavage of DNA isolated from cyanophages that infect Anabaena and Nostoc species of cyanobacteria has provided evidence for counter-selection of restriction endonuclease sites. These include sites containing subsequences which are methylated by host (Anabaena PCC 7120) methylase(s) akin to the dam and dcm enzymes of Escherichia coli. Other sites which are counter-selected have no common sequence structure. The latter include those of the endogenous restriction endonucleases of the host, but other absent sequences are not attributable to isoschizomers of any known Anabaena or Nostoc restriction endonuclease. The cyanophages differ in their tolerance to DNA methylation. Isolates A-4L, AN-13 and AN-23 do not tolerate adenosine methylation in the GATC sequence whereas two cyanophages, A-1L and AN-10 (which are related) do tolerate dam-like methylation of this sequence. In addition, A-1L allows cytosine methylation at GGCC sequences, but AN-10 has counter-selected these sequences and the remaining sites are not methylated. Analysis of native and cloned A-4L DNA suggests that counter-selection has occurred against all sequences which would be methylated by the host at either adenosine or cytosine nucleotides. [TOP OF PAGE]

  375. Comparative studies on the survival of indicator organisms and pathogens in fresh and sea water. Evison,L.M. (1988). Results are reported from a comprehensive series of experiments in which the survival characteristics of a range of indicator bacteria, pathogenic bacteria and bacteriophages was compared in fresh and seawater in the light, and at a range of temperatures, nutrient concentrations and salinities in the dark. Survival of the following organisms was studied: E. coli , faecal streptococci, maroon faecal streptococci, Salmonella typhimurium 12, 12a and 110, S. anatum, Shigella sonnei, Sh. flexneri , Yersinia enterocolitica, Campylobacter fetus , Coliphages MS 2 and f 2. The data shows that in the light the survival of E. coli was very poor compared to that of Salmonellae. In the light, survival was best in fresh water, but in the dark survival in seawater was usually better. A linear relationship was demonstrated for T sub(90) and light intensity, and log T sub(90) and temperature, but non-linear responses occurred for a range of salinities and nutrient concentrations. [TOP OF PAGE]

  376. Penetration of E. coli and F2 bacteriophage into fish tissues. Fattal,B., Dotan,A., Tchorsh,Y., Parpari,L., Shuval,H.I. (1988). SCHRIFTENREIHE DES VEREINS FUR WASSER-, BODEN-, UND LUFTHYGIENE 78:27-38. Throughout the world, fish thrive in rivers, lakes and seawater polluted with wastewater. Furthermore, in some countries, wastewater-enriched fishponds are used for fish cultivation. One of the major constraints in using wastewater for aquaculture is the possible contamination of the fish by enteric pathogens (bacteria and viruses), which may penetrate and accumulate in fish tissue, and constitute a potential public health hazard, especially in countries in which raw fish are consumed. In order to evaluate the infection of fish cultivated in wastewater, controlled experiments were performed to study the penetration of bacteria and bacteriophage inoculated into water tanks in which the fish were maintained. Twenty to thirty Tilapia hybrids (Sarotherodon aureus x S. niloticus), of 100 gr average weight and some 20 cm long were introduced into a 1 m3 plastic tank, containing about 500 l tap water at a temperature of 20 degrees C. High protein fish feed was added at a rate of about 1% of body weight per day. Four experiments were performed using an inoculum of an E. coli strain resistant to streptomycin and nalidixic acid. One hour after inoculation, bacterial concentration was 10(5)-10(6)/ml tank water. Four experiments were carried out with F2 male-specific bacteriophage 10(3)-10(5)/ml tank water. In each experiment two fish were sacrificed at zero time (prior to introduction of inocula), and 1, 5, 24, 48 and 72 or more hours after inoculation. Water samples were withdrawn at the same intervals. The level of microorganisms was tested in the following tissues: digestive tract, skin, spleen, liver and muscle. E. coli assays were performed using the membrane filtration technique; phages were assayed, using E. coli host cells in a plaque assay. The results of the experiments indicate that notwithstanding the high E. coli concentration in the tank water, its level in the edible tissue (muscle) was low, and in no instance higher than the acceptable standard of 400 cfu/gr (International Commission for Food Specification, 1974). The maximum concentration of F2 phage detected in muscle tissue was 350 pfu/gr. There is no standard for virus concentration in edible tissue. [TOP OF PAGE]

  377. Characterization of the bacteriophages infecting marine luminous bacterium Vibrio fischeri (Kaiyosei hakko-saikin Vibrio fischeri ni kansensuru bakuteriofaji no seijo). Hidaka,T., Kobayashi,M. (1988). Mem. Fac. Fish. Kagoshima Univ. /Kagoshimadai Suisangakubu Kiyo. 37:161-172. Twelve bacteriophages infecting the marine luminous bacterium Vibrio fischeri were isolated from seawater of Kagoshima Bay, (Japan), at 9 selected seasonal intervals during 1980 to 1982. Their lytic patterns, plaque morphology, particle structures, stabilities, one-step growth characteristics, and serological properties were observed. Each page had a strict host specificity. The phages varied considerably in particle structure and size; the phage heads were polyhedral with tails varying in length between 10 and 135 nm. Three of the phages had a short tail, six had a long and noncontractile tail, and three had a tail of complex structure with a contractile sheath. They also differed in serologic reactions. They were stable phages with double-stranded DNA as genetic material. These phages may provide a rapid and sensitive means of differentiating V. fischeri strains. [TOP OF PAGE]

  378. CHARACTERIZATION OF THE BACTERIOPHAGES INFECTING MARINE LUMINOUS BACTERIUM VIBRIO-FISCHERI. Hidaka,T., Kobayashi,M. (1988). Memoirs of the Faculty of Fisheries Kagoshima University 37:161-172. Characterization of the bacteriophages infecting marine luminous bacterium Vibrio fischeri.Twelve bacteriophages infecting marine luminous bacterium Vibrio fischeri have been isolated from seawater of Kagoshima Bay, at 9 times of selected seasonal intervals during 1980 to 1982. The lytic patterns, plaque morphology, particle structures, stabilities, one-step growth characteristics, and serological properties of them were observed. Each phage has a strict host specificity. The phages varied considerably in particle structure and size; the phage heads were polyhedral with tails varying in length between 10 and 135 nm. Three phages of them have a short tail, six have a long and noncontractile tail, and three have a tail of complex structure with a contractile sheath. They also differed from serologic reactions. They were stable phages with double-stranded DNA as genetic material. These phages may provide a rapid and sensitive means of differentiating V. fischeri strains. It seems that these data from a basis of the ecological studies of V. fischeri-phage systems in seawater. [TOP OF PAGE]

  379. Assessing immunocompetence of red drum (Sciaenops ocellatus ). Lewis,D.H., Thomas,P. (1988). Contributions in Marine Science 30:153-156. Immune responses were manifest in red drum (Sciaenops ocellatus ) following exposure of the fish to three immunogens, bovine erythrocytes, bovine serum albumin and Escherichia coli bacteriophage. These immunogens are frequently used to assess immunocompetence of man and other vertebrates following immunosuppressive treatment. Serologic responses to these materials are proposed as a method for assessing the potential effects of stressors and various other treatments upon host immunity in cultured fish. [TOP OF PAGE]

  380. Phages of cyanobacteria. Martin,E.L., Benson,R. (1988). pp. 607-645. In In Calendar,R. (ed.), The Bacteriophages. Volume 2. Plenum Press, New York. [TOP OF PAGE]

  381. Isolation and partial characterization of a bacteriophage active on Hyphomicrobium sp. WI-926. Preissner,W.C., Maier,S., Volker,H., Hirsch,P. (1988). Can. J. Microbiol. 34:101-106. Isolation of a Hyphomicrobium phage from raw sewage from Athens, Ohio, was achieved by a combination of differential centrifugation, filtration, enrichment in mixed Hyphomicrobium cultures, and purification on individual host strains by subculturing single plaques in soft agar overlayers. Enrichments with water from Lake Erie and Lake Beechwood (Ohio) were unsuccessful. Out of 21 Hyphomicrobium strains and 22 other Gram-negative and Gram-positive bacteria tested, only Hyphomicrobium WI-926 (isolated from a German forest pond) was susceptible. This phage had an isometric head (diameter between opposite apices, 67 nm) and a short (12 nm), noncontractile tail and belongs thus to the morphogroup C1. It contained double-stranded DNA. The single-step growth curve showed a latent period of 9 h, a rise period of 6 h, and a burst size of 35. The various differentiation stages in the host development exhibited different affinities for phage adsorption and development. While all stages allowed phage adsorption, the daughter cells were most efficient. Phage multiplication was limited to daughter cells, and the development of infected swarmer cells was arrested permanently at this stage. [TOP OF PAGE]

  382. Marine bacteriophages and bacterial mortality. Proctor,L.M., Fuhrman,J.A., Ledbetter,M.C. (1988). EOS 69:1111-1112. [TOP OF PAGE]

  383. Factors Affecting the Survival and Growth of Bacteria Introduced into Lake Water. Scheuerman,P.R., Schmidt,J.P., Alexander,M. (1988). Arch. Microbiol. 150:320-325. The populations of Pseudomonas sp. L2, Pseudomonas sp. B4, Escherichia coli, Klebsiella peneumoniae, Micrococcus flavus, and Rhizobium phaseoli declined rapidly in lake water. The initially rapid decline of the two pseudomonads and R. phaseoli was followed by a period of slow loss of viability, but viable cells of the other species were not found after 10 days. The rapid initial phase of decline was not a result of Bdellovibrio spp., bacteriophages, or toxins in the water since Bdellovibrio spp. were not present and passage of the lake water through filters that should not have removed bacteriophages or soluble toxins led to the elimination of the rapid phase of decline. We suggest that the decline in lake water of bacteria that are resistant to starvation may be a result of protozoan grazing and that the extent of growth of introduced species may be limited by the supply of available carbon and sometimes of nitrogen and phosphorus, and by predation by indigenous protozoa. [TOP OF PAGE]

  384. Cyanophage ecology. Cannon,R.E. (1987). pp. 245-265. In In Goyal,S.M., Gerba,C.P., and Bitton,G. (eds.), Phage Ecology. John Wiley & Sons, New York. [TOP OF PAGE]

  385. Isolation and characterization of a temperate cyanophage for a tropical Anabaena strain. Franche,C. (1987). Archives of Microbiology 148:172-177. In this paper we describe the isolation and characterization of a temperate cyanophage N(S)1 of the genus cyanopodovirus which produces turbid plaques on the host Anabaena 77815 isolated from tropical soil. Its properties have been compared to those of other well-characterized cyanophages. In addition, two strains of Anabaena 77815 lysogenic for N(S)1 were isolated. N(S)1 seems to be integrated into the chromosome of the two lysogens, and a 2 kb plasmid present at a low copy number in the non-lysogenic strain is amplified significantly. [TOP OF PAGE]

  386. An electron microscopic study of bacteriophages from marine waters. Frank,H., Moebus,K. (1987). Helgol. Meeresunters. 41:385-414. [TOP OF PAGE]

  387. Resistance of cultures of cyanobacteria Synechococcus cedrorum and Synechococcus parvula to AS-1K and S-8K cyanophages. Goryushin,V.A., Shainskaya,O.A. (1987). Mikrobiol. Zh. 48:74-78. Resistance of cultures of cyanobacteria Synechococcus cedrorum and Synechococcus parvula to AS-1K and S-8K cyanophages.Clones of unicellular cyanobacteria Synechococcus cedrorum and S. parvula having different susceptibilities to AS-1K and S-8K cyanophages were isolated, including clones with absolute resistance. Studies of age changes and culture conditions suggest that the resistance of the obtained cyanobacteria clones to virus infection is associated with a spontaneous mutation-induced modification in cell receptors. [TOP OF PAGE]

  388. Presence et distribution vertical de Microvibrio marinus dans les eaux de l'Ocean Antartique (secteur Indien) [Presence and vertical distribution of Microvibrio marinus in the Antartic Ocean (Indian).]. Guelin,A., Camus,P., Souchu,P. (1987). The bacterial predator Microvibrio marinus has been only observed in sea surface water. During the expedition SIBEX-MD42 the research objectives on this bacteria, from the surface to 4000m in depth, were carried out by the authors. The results obtained induced several questions about the sampling processes, the origin of these bacteria, their reproduction, their ecological requirements. [TOP OF PAGE]

  389. On the phage-sensitive bacteria in seawater of Kagoshima Bay (Kagoshima-wannai kaisui-chu no faji kanjusei saikin ni tsuite). Hidaka,T., Kamino,Y., Kawabe,K. (1987). Mem. Fac. Fish. Kagoshima Univ. /Kagoshimadai Suisangakubu Kiyo. 36:17-25. Marine bacteria and bacteriophages were isolated from seawater samples collected from 1 m and 50 m depth layers at 8 stations of Kagoshima Bay (Japan), at 11 times of selected seasonal intervals during 1980 to 1984. The isolates from each sample included several phage-sensitive strains. Their rate to total isolates from each sample varied from 0 to 87% (av. 25%), at each station, depth, and season. The sensitive strains were found in all genera of isolates, especially Pseudomonas, Vibrio, Aeromonas , and Moraxella . The strains were divided into several phage types in each genus. Their habitat was segregated into each station and depth. It was found that the strains of phage-type level have a habitat segregation dependent on the oceanographic conditions in the bay. [TOP OF PAGE]

  390. Changes in sensitivity to cyanophage infection in axenic LPP cyanobacteria. Johnson,D.W., Borovsky,D. (1987). Microbios Letters 35:105-112. [TOP OF PAGE]

  391. Isolation and characterization of a generalized transducing phage for the marine luminous bacterium Vibrio fischeri MJ-1. Levisohn,R., Moreland,J., Nealson,K.H. (1987). J. Gen. Microbiol. 133:1577-1582. A marine bacteriophage active against the marine luminous bacterium Vibrio fischeri MJ-1 was isolated from offshore waters in Ensenada, Baja California, Mexico, and was shown to be active in generalized transduction, transducing 14 of 17 different amino acid auxotrophs to prototrophy. For some of the amino acid auxotrophic markers, such as arginine and methionine, several different mutants could be transduced. The phage grew well at temperatures up to 27 degree C, and produced high-titre lysates (10 super(10) p.f.u. ml super(-1) or higher). Single-step growth analysis showed a latent period of 23 min at 25 degree C with a burst size of 100. Phage adsorption was maximum at NaCl concentrations characteristic of the marine environment. No evidence for lysogeny was found. [TOP OF PAGE]

  392. Isolation and characterization of a generalized transducing phage for the marine luminous bacterium Vibrio fischeri. Lindström,K., Kaijalainen,S. (1987). J. Gen. Microbiol. 82:241-246. [TOP OF PAGE]

  393. Ecology of Marine Bacteriophages. Moebus,K. (1987). pp. 137-156. In In Goyal,S.M., Gerba,G.P., and Bitton,G. (eds.), Phage Ecology. John Wiley & Sons, New York. [TOP OF PAGE]

  394. Evidence for lysogeny and viral resistance in the cyanobacterium Phormidium uncinatum. Bisen,P.S., Audholia,S., Bhatnagar,A.K., Bagchi,S.N. (1986). Curr. Microbiol. 13:1-5. Cyanophage LPP-1-induced lysogens and a resistant mutant of the cyanobacterium Phormidium uncinatum were isolated and characterized. In lysogens, spontaneous lysis occurred and increased with the growth of the host cyanobacterium. The virus-liberating property of the lysogens was not lost with the viricidal concentration of EDTA, and the titer obtained was > 3 plus or minus 10 super(3) PFU ml super(-1). Heat and UV treatment of lysogens failed to induce lysis, but mitomycin C induced lysis by fivefold. The adsorption rate of the virus on the lysogens was slower than on the sensitive parent host. [TOP OF PAGE]

  395. Myxobacterial predation of the cyanobacterium Phormidium luridum in aqueous environments. Burnham,J.C., Collart,S., Daft,M. (1986). Arch. Microbiol. 137:220-225. [TOP OF PAGE]

  396. Predatory Myxobacteria: Lytic Mechanisms and Prospects as Biological Control Agents for Cyanobacteria (Blue-Green Algae). Lake Restoration: Protection and Mangement. Burnham,J.C., Fraleigh,P. (1986). U.S.EPA Symposium Volume EP-A4401/583001, 249-256. To control problem growths of primary producers in lakes and ponds, especially blooms of blue-green algae and high densities of macrophytes, a diversity of methods have been proposed and are used. However, absent in this repertoire are methods of biological control analogous to those that have been successful in terrestrial ecosystems. Presented here is a discussion of studies that suggest that myx- obacterial predation may be useful in biological control of blue-green algae in aquatic ecosystems. algae and high densities of macrophytes, a diversity of methods have been proposed and are used. However, absent in this repertoire are methods of biological control analogous to those that have been successful in terrestrial ecosystems. Presented here is a discussion of studies that suggest that myx- obacterial predation may be useful in biological control of blue-green algae in aquatic ecosystems. [TOP OF PAGE]

  397. Properties of some Aeromonas salmonicida -virulent phages isolated in Japan (Honpo de bunrisareta Aeromonas salmonicida -birurento phaji no tokusei). Hidaka,T., Kawaguchi,T. (1986). Mem. Fac. Fish. Kagoshima Univ. /Kagoshimadai Suisangakubu Kiyo. 35:39-52. Virulent bacteriophages specific for Aeromonas salmonicida were isolated from water samples collected from fish farms, rivers, lakes and marshes in Japan. The isolated phages differed greatly in the fine structure of the virion, plaque morphology, spectrum of lytic action, stability and one-step growth characteristics, but they had identical serological properties. They were classified into five groups. Group 1 phages consisted of an elongated hexagonal head and a tail of complex structure with a contractile sheath. The phages of groups 2, 4 and 5 had a hexagonal head and a tail with a contractile sheath. Group 3 phages exhibited a hexagonal head with a unique short tail, formed the largest clear plaque, were unstable to heating at 50 degree C for 30 min. and chloroform, and showed the shortest latent period. Phage typing with representative phage of each group may provide a rapid and sensitive means of differentiating A. salmonicida strains. [TOP OF PAGE]

  398. [The structure of cyanobacterial phycobilisomes and its change in viral infection]. Mendzhul,M.I., Averkiev,A.A. (1986). Mikrobiol Zh 48:89-101. [TOP OF PAGE]

  399. [Role of temperate phage in bacterial dissociation]. Mil'ko,E.S., Egorov,N.S. (1986). Nauchnye doklady vysshei shkoly Biologicheskie nauki 6-19. The analysis of literary and own data testifies that the dissociants may appear in bacteria population from spontaneous mutations and transfer of genetic material (conjugation, transformation, transduction). The phage conversion and different DNA reorganizations within a cell where prophage plays an active role, probably introduce the largest contribution into the dissociative transitions of variants which occur with high frequency (about 10(-2)-10(-4). The dissociation of various bacteria has been studied with different degree. The role of temperate phage has been shown in splitting of bacteria into variants in the genera Mycobacterium, Corynebacterium, some Bacillus, Clostridium, Staphylococcus, some enterobacteria, Yersinia, Vibrio Pseudomonas, Rhizobium, Nostoc; the participation of prophage in dissociation of bacteria of the genera Xanthomonas, Erwinia, Bacteroides is proposed. A method for obtaining the nondissociating S-variants for stability of biologically active substances synthesized by cells has been suggested. [TOP OF PAGE]

  400. Survival strategies of two small marine ciliates and their role in regulating bacterial community structure under experimental conditions. Turley,C.M., Newell,R.C., Robins,D.B. (1986). Mar. Ecol. Prog. Ser. 33:59-70. [TOP OF PAGE]

  401. BACTERIOPHAGES OF METHANOTROPHS AND THEIR DISTRIBUTION IN NATURE. Tyutikov,F.M., Bespalova,I.A., RABENTISH,B.A., ESIPOVA,V., V, Aleksandrushkina,N.N., Tikhonenko,A.S. (1986). Izvestiya Akademii Nauk SSSR Seriya Biologicheskaya 361-369. Bacteriophages of methanotrophs and their distribution in nature.Bacteriophags of methanotrophs are spread widely in nature: they were found in 18 from 100 analyzed samples (underground waters, waters of oil-gas-installations, water of lakes and ponds, culture liquid of fermenters, paste of methanotrophs, rumen of cattle, intestine of fishes), collected in different geographical zones of the USSR. 25 phages, 10 of which are capable of lyse strains of Methylosinus sporium only, 2 strains lyse Methylosinus trichosporium, 12 strains lyse Flavobacterium gasotypicum and, besides this, one of strains of M. sporium, one strain lyses Methylocystis species, were isolated. According to the fine stucture of virion all phages are divided into 2 types: one type is characterized by short uncontracted processes and the long ones. According to morphology of negative colonies and sensitivity of phages to UV-radiation the phages are divided into 3 groups, according to serology.sbd.into 4 groups, according to spectrum of lytic effect.sbd.into 5 groups. All phages have two-chain DNA of GC-type. Molecular mass of DNA, determined by way of restricted nucleases was equal: for strains of M. sporium phagess-29.4, for strains of M. species phages-28, for strains of F. gasotypicum phages-44 and for strain cmph-1 -31 MD. The phages of the particular group were completely identical in all mentioned properties, but differed from the phages of the groups. Phage cmph-1 was differed from 11 phages of F. gasotypicum by a number of features. [TOP OF PAGE]

  402. Mutation to resistance for virus AS-1 in the cyanobacterium Anacystis nidulans. Bisen,P.S., Audholia,S., Bhatnagar,A.K. (1985). Microbiol. Lett. 29:7-13. [TOP OF PAGE]

  403. Coliphage survival in seawater. Borrego,J.J., Romero,P. (1985). Water Res. 19:557-562. The relative survival of coliphages isolated from seawater under controlled conditions in different media, in the laboratory and in the marine environment, was investigated. The results show that the survival under controlled conditions in different media, and also in the sea, is affected by biological and chemical factors. In the sea there are several other important factors, and combinations of these, which are difficult to reproduce in the laboratory (DBO). [TOP OF PAGE]

  404. Properties of new marine bactericidal Microvibrios. Finance,C., Durand,M. (1985). Archives Roumaines de Pathologie Experimentales et de Microbiologie 44:99-108. [TOP OF PAGE]

  405. Host range of LPP cyanophages. Johnson,D.W., Potts,M. (1985). International Journal of Systematic Bacteriology [INT. J. SYST. BACTERIOL. ] 35:76-78. The authors determined the sensitivities of 33 strains and variants of cyanobacteria to infection by the cyanophage LPP-1 archaetype, five LPP-1 serotypes, six LPP-2 serotypes, and 8 new LPP isolates. The LPP-1 archaetype and LPP-1 serotypes have different host ranges on strains of LPP group B. [TOP OF PAGE]

  406. Comparison of selective media for assay of coliphages in sewage effluent and lake water. Kennedy,J.E., Jr., Bitton,G., Oblinger,J.L. (1985). Appl. Environ. Microbiol. 49:33-36. Selective media, including EC medium, gram-negative broth, nutrient broth (with 0.05% sodium deoxycholate), and lactose broth (with 0.05% sodium deoxycholate), as well as nonselective nutrient and lactose broth, were compared for the enumeration of coliphages by the agar layer method from activated sludge or after chloroform treatment with Escherichia coli B, E. coli C, or a mixed host of both E. coli B and C. With the exception of gram-negative broth, direct assays of all samples with the selective media generally resulted in significantly higher (P< 0.05) recoveries of coliphages than did assays of chloroform-treated samples with nutrient broth medium regardless of the host used. In addition, chloroform pretreatment resulted in decreased recovery of coliphages with each selective medium in most analyses. The highest recoveries of coliphages from all samples with each host, except lake water with E. coli C, were obtained by direct assay on EC medium. The selectivity of the EC and gram-negative media resultsed in suppression of bacterial interference on direct assay plates compared to that observed in nutrient agar medium with chloroform-treated samples. The use of certain selective media for the direct assay of environmental materials for coliphage may enhance the recovery of coliphages and obviate bacterial decontamination procedures. [TOP OF PAGE]

  407. A survey for viruses from fresh water that infect a eukaryotic Chlorella-like green alga. van Etten,J.L., van Etten,C.H., Johnson,J.K., Burbank,D.E. (1985). Appl. Environ. Microbiol. 49:1326-1328. [TOP OF PAGE]

  408. The water quality of water-holes utilised by game in the Etosha National Park. Winter,C.T. (1985). Madoqua. 14:145-153. Water quality surveys undertaken in the Etosha National Park between October 1974 and August 1979, indicated that the water-holes in the area are faecally contaminated. The bacteriological quality is worst during the dry season. Eighteen per cent of the water-holes tested failed to meet the chemical Livestock Drinking Water Standard (D standard) of the Department of Water Affairs, South West Africa. Most anthrax outbreaks occur in the wet season and also within the anthrax areas, indicating that the chemical quality of the water alone cannot be implicated in the occurrence of the disease. Bacillus anthracis bacteriophage (anthraphage) was mainly isolated from water-holes situated outside the enzootic anthrax areas and also with greater frequency during the dry season, indicating that this bacteriophage might be implicated in preventing the disease. [TOP OF PAGE]

  409. The effect of suspended particular material on cyanobacteria-cyanophage interactions in liquid culture. Barnet,Y.M., Daft,M.J., Stewart,W.D.P. (1984). J. Appl. Bacteriol. 56:109-115. The effect of the lytic phage LPP-DUNI on the cyanobacterium Plectonema borya has been investigated in batch and in continuous cultures in the presence and absence of silt. In batch culture Plectonema without added phage grew normally: the presence of phage caused rapid lysis of the cyanobacterium and the addition of the prevented lysis of the cyanobacterium and the addition of the prevented lysis by the phage. In continuous culture the numbers of cyanobacterial cells and phage particles oscillated in a reciprocal manner, but the addition silt damped down the oscillations in Plectonema biomass without decreasing the numbers of phage particles isolated from the cultures. [TOP OF PAGE]

  410. Control of microbiofouling formed on the heat exchanger by bacteriophage. Kaminura,K., Araki,M. (1984). pp. 40-46. In AnonymousProceedings of the Pacific Congress on Marine Technology (Honolulu, Hawaii). The surface of the heat exchangers using natural seawater is usually covered with the microbial films formed by the attachment and growth of marine bacteria during their operation. The formation of the microbial film lowers the total heat transfer coefficient because of its low thermal-conductivity and then leads to the decrease of the efficiency of the heat exchanger system. In the OTEC system which utilizes the small temperature difference between warm surface water and cold depth water as energy source, it becomes important to control the marine microbiofouling. This report, discusses the isolation and characterization of marine bacteriophages which lyse fouling bacteria and the application of bacteriophages to controlling a marine microbiofouling. [TOP OF PAGE]


  412. Effects of pesticides on cyanobacterium Plectorema boryanum and cyanophage LPP-1. Mallison,S.M.I., Cannon,R.E. (1984). Appl. Environ. Microbiol. 47:910-914. Cyanobacterium Plectonema boryanum IU 594 and cyanophage LPP-1 were used as indicator organisms in a bioassay of 16 pesticides. Experiments such as spot tests, disk assays, growth curves, and one-step growth experiments were used to examine the effects of pesticides on the host and virus. Also, experiments were done in which host or virus was incubated in pesticide solutions and then assayed for PFU. P. boryanum was inhibited by four herbicides: 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 1,1-dimethyl-3-(alpha, alpha,alpha-trifluoro-m-tolyl)urea ( Fluometeron ), 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (Atrazine), 2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine ( Ametryn ). One insecticide, 2-methyl-2-(methylthio)-propionaldehyde O-( methylcarbamoyl )oxime (Aldicarb), also inhibited the cyanobacterium. Two insecticides inactivated LPP-1, O,O-dimethyl phosphorodithioate of diethyl mercaptosuccinate (malathion) and Isotox . Isotox is a mixture of three pesticides: S-[2-( ethylsulfinyl )ethyl]O,O-dimethyl phosphorothioate ( Metasystox -R), 1-naphthyl methylcarbamate ( Sevin ) and 4,4'-dichloro-alpha- (trichloromethyl) benzhydrom ( Kelthane ). Two pesticide-resistant strains of P. boryanum were isolated against DCMU and Atrazine. These mutants showed resistance to all four herbicides, which indicates a relationship between these phototoxic chemicals. The results indicate that P. boryanum may be a useful indicator species for phototoxic agents in bioassay procedures. [TOP OF PAGE]

  413. Metabolic aspects of cyanophage AS-1 replication and reproduction in cyanobacterium Anacystis nidulans. Amla,D.V., Saxena,P.N. (1983). Biochem. Physiol. Pflanz. 178:225-236. The intracellular stages of the cyanophage AS-1 replication cycle were investigated under conditions that impair the metabolic functions of the host, A. nidulans . The reproductive cycle of the cyanophage consists of an eclipse period (3.5 h), latent period (7 h) and finally lysis of cells after 14 h with the release of 100-120 PFU/infected cell. Viral multiplication was inhibited in dark. Withdrawal of light before the eclipse period or incubation of the infected cells in the dark for 6 h followed by illumination, decreased the final yield of virus and prolonged the reproductive cycle. The inhibitor of Photosystem II, DCMU, prolonged the latent period and reduced the burst-size to 50-60% of the control. Inhibitor of electron transport, CCCP, abolished the viral growth completely. Treatment of infected cells with chloramphenicol up to 4 h during the latent period completely abolished the phage growth. These results demonstrated the dependent virulent nature of the cyanophage AS-1. [TOP OF PAGE]

  414. Sensitivity of coliphage T1 to nickel in fresh and salt waters. Babich,H., Schiffenbauer,M., Stotzky,G. (1983). Curr. Microbiol. 8:101-105. Coliphage T1 was more sensitive than its host bacterium, Escherichia coli B, to nickel (Ni). A 5-exposure to 100 ppm Ni in nutrient broth did not adversely affect T1, whereas 10 and 20 ppm Ni extended the lag phase of growth of E. coli B, and no growth occurred with 40 or more ppm Ni. 5 ppm Ni enhanced the survival (after 4 wk) of T1 in sea or simulated estuarine water but was toxic (i.e., reduced viral infectivity) in lake water; 50 ppm Ni was not toxic to T1 in sea water, was moderately toxic in estuarine water, but was highly toxic in lake water; and 100 ppm Ni was toxic in all systems, with the sequence of loss in viral infectivity being lake > estuarine > sea water. 100 ppm Ni was not toxic to T1 in nutrient broth, even after 3 wk of exposure, probably because of the protective effect of the organic compounds in the broth. [TOP OF PAGE]

  415. Preliminary study of microbial inactivation in the marine environment. Borrego,J.J., Arrabal,F., Vicente,A., Gomez,L.R., Romero,P. (1983). Journal Water Pollution Control Federation 55:297-301. Data collected at a marine outfall show that most bacterial species underwent an initial dilution of over 90%. Salmonella-Shigella loses its viability most rapidly, perhaps because of poor adaptive capacity. However, the overall degree of inactivation achieved, in descending order, are total coliform, fecal coliform, Salmonella-Shigella , coliphage, and fecal streptococci. Using Escherichia coli -specific bacteriophage as a pollution indicator is an attractive consideration, but further studies seem to be necessary. [TOP OF PAGE]

  416. Aerosol release of cyanophages and coliforms from activated sludge basins. Cannon,R.E. (1983). Journal Water Pollution Control Federation 55:1070-1074. Aerosol release of cyanophages and coliforms from activated sludge basins.Aerosol release of cyanophages and coliforms from activated sludge basins at 2 wastewater treatment plants in Greensboro, North Carolina [USA] was studied. One uses diffused aeration in the treatment process and the other, mechanical aerators. Detection methods consisted of mechanical air samplers and stationary sampling sites using petri dishes open to the air for varying times. Samples were taken weekly for 1 yr to ensure that virus dispersal was studied under a variety of weather conditions. There were considerably more aerosols when aeration was mechanical instead of diffused. Wind direction seemed to be an important environmental factor in the spread of viruses and coliforms from the basins. Cyanophages, which were found more readily than coliforms throughout the year, may serve as effective indicators for aerosol wastewater contamination. [TOP OF PAGE]

  417. Cyanophage: Histroy and likelihood as a control. Desjardins,P.R. (1983). pp. 242-248. In AnonymousLake Restoration, Protection, and Management. Environmental Protection Agency, Washington, D.C. It has been 20 years since the first cyanophage was discovered. Since then additional cyanophages and strains that infect both unicellular and filamentous cyanobacteria have been found. Cyanophages are similar to other bacteriophages in many physical, chemical and biological characteristics, but dif- fer from them in their requirement of light for absorption to their hosts and their dependence upon the photosynthetic activity of their hosts for their replication. Light quality and the ratio of red to far- red light affect virus replication. Cyanophages play a distinctive role in the ecology of their hosts and probably are effecting some natural control. Certain factors (development of resistant host strains, specific ion requirements, environmental factors and lysogeny) may affect the potential of the cyanophages to control their hosts, but these have not been conclusively shown to completely destroy this potential. There is much need for additional research on the experimental control of nuisance species in natural water bodies. Preliminary studies suggest that the phages may be more effective in preventing blooms than in eliminating one already formed. An integrated approach involving several biological techniques is recommended for control of nuisance populations of cyanobacteria. [TOP OF PAGE]

  418. Viral Control of Nuisance Cyanobacteria (Blue-Green Algae). II. Cyanophage Strains, Stability on Phages and Hosts, and Effects of Environmental Factors on Phage-Host Interactions. Desjardins,P.R., Olson,G.B. (1983). California Water Resource Center, University of California, Davis, CA.Differentiation of phage strains in the AS cyanophage group was accomplished. Studies on Anabaena cyanophages (A-1 , A-4, and AN-lo), which originally were received from Russia, demonstrated that the A-4 preparation was actually a mixture of a lytic (AN-10) phage and a temperate (A-4) phage. An additional strain of Anabaena variabilis was shown to be a host of all three phages in the group. ¶ Antiserum to the LPP-1 cyanophage with a relatively high titer was prepared for later use in cyanophage detection. Storage by simply freezing in culture media permitted some cyanobacterial species to survive for several months. Failure of other species to survive under identical conditions indicates a need for additional research in this area. The adverse effects of freezing on virion structure and infectivity were characterized for the AS-1 and LPP-1 cyanophages. ¶ Bloom concentrations of Plectonema boryanum were established in outdoor pond facilities. Some control of this cyanobacterial species was effected with the LPP-1 cyanophage. Results suggest that the cyanophage is most effective when present before the bloom develops. ¶ Studies on the effect of temperature on the growth cycle of AS-1 cyanophage demonstrated that the length of the cycle varied inversely with temperature in the range 25-36°C. The importance of light quality in the growth cycle of this cyanophage has also been shown. Of special significance is the finding that the red/far red light ratio can greatly influence the yield of AS-1 in Anacystis niduIans. [TOP OF PAGE]

  419. Cyanophages. Gromov,B.V. (1983). Ann. Microbiol. (Inst. Pasteur) 134B:43-59. The description of cyanophages isolated in the USSR is given. The data presented here primarily concern cyanophages of A(L) and S(L) series developing in the cells of Anabaena variabilis strains of Synechococcus species strains, respectively. [TOP OF PAGE]

  420. Factors affecting the enumeration of coliphages in sewage and sewage-polluted waters. Havelaar,A.H., Hogeboom,W.M. (1983). Antonie van Leeuwenhoek 49:387-397. The count of coliphages in naturally polluted waters was found to be dependent on many experimental factors. If Escherichia coli C was used as a host strain, consistently higher counts were obtained than with other strains (B, K-12-derivatives). This could be explained partly by the absence of a restriction system in C. A nutrient medium (modified Scholtens' agar, MSA) was developed with optimal concentrations of calcium- and magnesium-ions. MSA was compared with other media used for phage work and was found to give higher counts than all but one medium, Phage Assay Agar (PAA), which performed equally. If plating was done in a single agar layer in a large-size Petri-dish, higher counts were found than with the well-known double-agar-layer method. [TOP OF PAGE]

  421. Effect of incubation temperature and mineral environment on the propagation of marine bacteriophages (Kaiyo bacteriophages no zoshoku ni oyobosu baiyo ondo to baichichu mukien no eikyo). Hidaka,T. (1983). Mem. Fac. Fish. Kagoshima Univ. /Kagoshima-Dai Suisangakubu Kiyo. 32:133-146. The effects of culture conditions, temperature and mineral composition, on the propagation of five bacteriophage systems isolated from sea water were investigated. For the test a one-step growth experiment method was used. One cycle of phage propagation was observed, i. e. adsorption, multiplication, and burst, and the results were as follows: The host bacteria grew within the temperature range of 17 degree to 35 degree C with optimum at 32 degree C, but the phages propagated only between 25 degree and 28 degree C with optimum at 25 degree C. The host bacteria showed different behaviour regarding the mineral requirement for growth. Two of them required media supplemented by 3% NaCl for growth, and the other three required K-, Mg-, and Ca-salt as well as NaCl. All of the tested phages propagated only in the same mineral conditions as sea water. These results demonstrate that temperature and mineral conditions for the phage propagation in the host cell are more restrictive than those for the growth of the host bacterium alone. The properties of the tested phages, psychrophilic and specific mineral requirements for propagation, defined them as marine phages. [TOP OF PAGE]

  422. A simplified method for coliphage detection in natural waters. Isbister,J.D., Simmons,J.A., Scott,W.M., Kitchens,J.F. (1983). Acta Microbiol. Pol. (B Microbiol. Appl. ). 32:197-206. The ARCAT (A Rapid Coliphage Analysis Technique) method for detecting coliphages in water has been modified. Modifications to the original method include media optimization, the use of frozen host cultures, the use of a single agar coliphage assay and optimized plaque resolution with 2,3,4-triphenyltetrazolium chloride. Detection of 5 coliphages per 100 ml of water is accomplished in 6 hours for rapid estimation of water quality. [TOP OF PAGE]

  423. Taxonomic investigations of bacteriophage sensitive bacteria isolated from marine waters. Moebus,K., Nattkemper,H. (1983). Helgol. Meeresunters. 36:357-373. Based on 28 criteria the taxonomy of 366 phage sensitive bacterial strains isolated from marine waters (Atlantic between European continental shelf and Sargasso Sea, Bay of Biscay, North Sea near Helgoland) was investigated. Seventy-eight phage-intensity strains derived from the same Atlantic Ocean regions as the sensitive ones were tested for comparison. While in the latter considerable diversity was observed, the results obtained with the phage-sensitive bacteria are characterized by stupendous uniformity. 362 of the 366 strains are assigned to the family Vibrionaceae, some 280 of which belong to the genus Vibrio. [TOP OF PAGE]

  424. Lytic and inhibition responses to bacteriophages among marine bacteria, with special reference to the origin of pahge-host systems. Moebus,K. (1983). Helgol. Meeresunters. 36:375-391. [TOP OF PAGE]

  425. Classification and nomenclature of viruses of cyanobacteria. Safferman,R.S., Cannon,R.E., Desjardins,P.R., Gromov,B.V., Haselkorn,R., Sherman,L.A., Shilo,M. (1983). Intervirology 19:61-66. [TOP OF PAGE]

  426. Collapsing Aphanizomenon flos aquae blooms: Possible contributions of photo-oxidation, oxygen toxicity and cyanophages. Coulombe,A.M., Robinson,G.G.C. (1982). Canadian Journal of Botany 59:1277-1284. Triggering mechanisms for collapse of A. flos-aquae (L.) Ralfs blooms in 3 shallow eutrophic pothole lakes (L 885, L 958 and L 522), located within an aquaculture project study area in southwestern Manitoba, Canada, were examined. Three of the collapses observed (L 885, mid-July 1979; L 958, mid-Aug. 1979; and L 522, mid-July 1979) were initiated during periods of lake thermal stability when conditions conducive to photo-oxidation and/or death due to O2 toxicity were operable. A 4th collapse (L 958, mid-Aug. 1973) was initiated during a period of lake thermal instability when photo-oxidation and O2 toxicity could be dismissed as triggering mechanisms. The possibility of cyanophage-induced algal lysis causing bloom collapse was considered and morphological evidence for the occurrence of viruslike particles (vlps) within Aphanizomenon cells from L 885 (1979) and L 958 (1978, 1979) are presented. Since transmission and isolation of the vlps was not substantiated, the verification of a virus infection of the Aphanizomenon populations studied is not yet possible. No single triggering mechanism can account for all of the algal collapses described. [TOP OF PAGE]

  427. Applications of a Serratia marcescens bacteriophage as a new microbial tracer of aqueous environments. Drury,D.F., Wheeler,D.C. (1982). J. Appl. Bacteriol. 53:137-142. A bacteriophage of S. marcescens was evaluated as a tracer in three appropriate aqueous environments and compared with an accepted tracer in two cases. The phage compared favourably with lithium chloride in demonstrating flow characteristics and retention times of various stages in the sewage treatment process. The phage exhibited virtually identical distribution in a marine harbour to spores of Bacillus subtilis var. niger (B. globigii ) 36-48 h after their addition to a sewage works' final effluent which entered an adjacent bay. Transit times of river water were accurately measured between two points under various flow conditions. [TOP OF PAGE]

  428. PLEIOTROPIC BEHAVIOR OF A CYANO PHAGE AS-1 RESISTANT MUTANT OF ANACYSTIS-NIDULANS. Kashyap,A.K., GUPTA,S.L. (1982). Mol. Gen. Genet. 185:365-366. Pleiotropic behavior of a cyanophage AS-1-resistant mutant of Anacystis nidulans.A cyanophage AS-1 resistant mutant strain of A. nidulans exhibited a slow rate of nutrient uptake compared to the wild type. The increased Ca2+ sensitivity of the mutant could be correlated with higher rates of Cu2+ uptake. The results are discussed in the light of alterations in the proteins involved in permeability of the outer membrane. [TOP OF PAGE]

  429. The use of microorganisms as ground-water tracers: A review. Keswick,B.H., Wang,D.S., Gerba,C.P. (1982). Ground Water 20:142-149. Microbial contamination of ground water results in numerous disease outbreaks each year. Tracing their movement in ground water is therefore essential. Bacteria, viruses, yeasts and spores have been used for this purpose and to trace underground movement of water in much the same manner as chemical tracers are used. Chemical tracers do not always reflect the movement of microorganisms in ground water. Bacterial viruses appear to be the microorganisms most suited as a microbial tracer because of their size, ease of assay and lack of pathogenicity. Bacteriophages have been used to trace ground-water movement over distances of 1,600 meters and can be used under a variety of conditions. [TOP OF PAGE]


  431. AS1 cyanophage adsorption to liposomes. Oliveira,A.R., Mudd,J.B., Desjardins,P.R. (1982). J. Gen. Virol. 61:153-156. [TOP OF PAGE]

  432. The effet of light and temperature on the generation time, adsorption, and yield of the cyanophages AS-1. Olson,G.B., Desjardins,P.R. (1982). Phytopathology 72:937 [TOP OF PAGE]

  433. Antiviral activity of antibiotic-producing marine bacteria. Toranzo,A.E., Baria,J.L., Hetrick,F.M. (1982). Can. J. Microbiol. 28:231-238. [TOP OF PAGE]

  434. Isolation of characteristics of minute plaque forming mutant of cyanophage AS-1. Amla,D.V. (1981). Biochem. Physiol. Pflanz. 176:83-89. Isolation of characteristics of minute plaque forming mutant of cyanophage AS-1.Minute plaque forming mutant (m) of cyanophage AS-1 infecting unicellular blue-green algae, Anacystis nidulans, was isolated spontaneously and after mutagenic treatment. Compared to wild type m mutant-formed small plaques, adsorption rate was slow and the burst-size was significantly decreased with prolonged eclipse and latent period. The plaque forming ability of mutant phage was sensitive to pH, heat, EDTA shock, distilled water and photosensitization with acriflavine; UV sensitivity of free and intracellular phage was identical to the parent. The spontaneous reversion frequencies of mutant phage to wild-type were between 10-5-10-3, and appeared to be clonal property. Reversion studies suggested possibilities of frame-shift or base-pair substitution for m mutation. [TOP OF PAGE]

  435. Chelating agent shock of cyanophage AS-1 infecting unicellular blue-green algae, Anacystis nidulans. Amla,D.V. (1981). Indian J. Exp. Biol. 19:209-211. Chelating agent shock of cyanophage AS-1 infecting unicellular blue-green algae (Anacystis nidulans).Three strains of free cyanophage AS-1 (wild, host-range h and minute plaque forming m) exposed to chelating agents were inactivated by chelating agent shock (CAS) when diluted rapidly in distilled water. The intracellular phage particles were comparatively resistant to CAS inactivation. Susceptibility of all the phage strains to CAS was enhanced with increases in concentration of chelating agents, time and temperature of the shocking water. Addition of monovalent or divalent salts but not the nonionic solutes to the shocking water resulted in protection of phage particles; addition of these salts to the shocking water after CAS treatment did not promote recovery of phage infectivity. Inactivation of cyanophages by CAS is probably due to interaction of the polyanionic chelating agents with the cations present in phage protein. In the course of rapid dilution the native structure of cyanophage particles is distorted, resulting in inactivation of phages. [TOP OF PAGE]

  436. Cyanobacteriophage interactions on the replication of cyanophage SM-2. Barnet,Y.M., Daft,M.J., Stewart,W.D.P. (1981). J. Appl. Bacteriol. 51:541-552. [TOP OF PAGE]

  437. Cyanobacteria-cyanophage interactions in continuous culture. Barnet,Y.M., Draft,M.J., Stewart,W.D.P. (1981). J. Appl. Bacteriol. 51:541-552. [TOP OF PAGE]

  438. Effects of photosynthetic inhibitors and light-dark regimes on the replication of cyanophage SM-2. Benson,R., Martin,E. (1981). Archives of Microbiology 129:165-167. [TOP OF PAGE]

  439. Recovery of coliphages from wastewater effluents and polluted lake water by the magnetite-organic flocculation method. Bitton,G., Chang,L.T., Farrah,S.R., Clifford,K. (1981). Appl. Environ. Microbiol. 41:93-96. A magnetite-organic flocculation method was developed for the concentration of coliphages from wastewater effluents and polluted lake water. A high percent (68 to 100%) recovery of coliphages from sewage effluents was achieved by this procedure. Coliphage recovery from Lake Alice, a sewage-contaminated lake, showed phage concentrations ranging from 2.3 X 10(2) to 1.9 X 10(3) plaque-forming units per liter. This method is simple and inexpensive and may be carried out under field conditions. [TOP OF PAGE]

  440. Cyanophages--are they potential biological control agents of nuisance blue-green algae? Desjardins,P.R. (1981). E-81-7, 198-229. Pacific Grove, California. Proc.Workshop Algal Manage.Control. 1980.[TOP OF PAGE]

  441. New Anabaena and Nostoc cyanophages from sewage settling ponds. Hu,N.-T., Thiel,T., Gidding,T.H., Jr., Wold,C.P. (1981). Virology 114:236-246. [TOP OF PAGE]

  442. Bacteriophage sensitivity patterns among bacteria isolated from marine waters. Moebus,K., Nattkemper,H. (1981). Helgol. Meeresunters. 34:375-385. Phage-host cross-reaction tests were performed with 774 bacterial strains and 298 bacteriophages. The bacteria (bacteriophages) were isolated at different times from water samples collected in the Atlantic Ocean between the European continental shelf and the Sargasso Sea: 733 (258) strains; in the North Sea near Helgoland: 31 (31) strains; and in the Bay of Biscay; 10 (9) strains. Of the Atlantic Ocean bacteria 326 were found to be susceptible to one or more Atlantic Ocean bacteriophage(s). The bacteriophage sensitivity patterns of these bacteria vary considerably, placing 225 of them in two large clusters of bacteriophage-host systems. Taking all into account, 250 of the 326 Atlantic Ocean bacteria are different from each other. This high degree of variation among the bacteria distinguishes microbial populations derived from widely separated eastern and western regions of the Atlantic Ocean. [TOP OF PAGE]

  443. Sequence of morphological alterations in blue-green algae in the course of cyanophage infection. Moisa,I., Sotropa,E., Velehorschi,V. (1981). Virologie 32:133-137. Electron microscopic studies were performed on the sequence of morphological alterations induced by the cyanophage PP-1 in the blue-green algae Phormidium sp. and Plectonema boryanum. The following phases of virus infection were made evident: virus adsorption onto the host cell; the presence of virus “ghosts”, suggesting the penetration of viral DNA into the cell and its multiplication in the nucleoplasm; invagination of thylakoids and formation of the “virogenic stroma”; virus maturation within the “virogenic stroma”; cellular lysis at 48 hours post inoculation. [TOP OF PAGE]

  444. Investigation on the presence of cyanophages in fresh and sea waters of Romania. Moisa,I., Sotropa,E., Velehorschi,V. (1981). Virologie 32:127-132. Investigations on the presence of cyanophages in the fresh and sea waters of Romania resulted in the isolation of 31 strains. The host range of the cyanophage isolates showed some particularities as compared with classical cyanophages types. The electron optic study of the cyanophage strains grown in Phormidium sp. revealed the presence of three types of virus particles, differing as regards their tail length, with a morphology similar to that of T-odd coliphages. [TOP OF PAGE]

  445. The immune response of the Antarctic teleost Notothenia rossii to the bacteriophage MS2. O'Neill,J.G. (1981). Bull. Br. Antarct. Surv. 21-27. The primary and secondary humoral immune responses to single intraperitoneal inoculations of MS2 bacteriophage were followed in Notothenia rossii , maintained at 2 degree C in experimental aquaria. All the specimens examined were immuno-competent and produced IgM-like neutralization antibody. The antibody titre curves were typical of responses to viral immunogen observed in higher vetebrates but the clearance of bacteriophage and the latent, or inductive, phase of the primary response were prolonged. The secondary response indicated immune memory with a reduced latent phase, followed by enhanced and maintained antibody titres. Adjuvants were found to have little effect on antibody titre but they did enhance the clearance of the bacteriophage from the sera. [TOP OF PAGE]

  446. Humoral Immune Response of Salmo trutta L. and Cyprinus carpio L. Exposed to Heavy Metals. O'Neill,J.G. (1981). Journal of Fish Biology 19:297-306. Salmo trutta L. and Cyprinus carpio L. were exposed to low levels of waterborne heavy metals, 0 multiplied by 75 mg Ni dm super(-3), 1 multiplied by 06 mg Zn dm super(-3), 0 multiplied by 29 mg Cu dm super(-3) and 1 multiplied by 01 mg Cr dm super(-3). atpH 7 multiplied by 83, water hardness 206 multiplied by 9 mg CaCO sub(3) dm super(-3), and water temperature 15 multiplied by 5 degree C. During a 38 week exposure period, the humoral antibody response to MS2 bacteriophage was followed using a 50% viral neutralization assay (SD sub(50)) method. A suppression of the immune response was observed in fish exposed to the four heavy metals. The time for the primary blood clearance of live bacteriophage was increased in S. trutta exposed to the heavy metals, with the exception of Zn-exposed fish, and in C. carpio exposed to Cu. Following the suppressed primary responses, the Ni-exposed S. trutta and Zn-exposed C. carpio exhibited an adjuvant-like response to the second bacteriophage challenge. [TOP OF PAGE]

  447. Reduction in the inactivation rates of bacteriophages by clay minerals in lake water. Babich,H., Stotzky,G. (1980). Water Res. 14:185-187. [TOP OF PAGE]

  448. Bacteriophage infection intereres with quanosine 3'-diphosphate-5'-disphosphate accumulation induced by energy and nitrogen starvation in cyanobacterium Anacystis nidulans. Borbéy,G., Kari,C., Gulyas,A., Farkas,G.L. (1980). J. Bacteriol. 144:859-864. [TOP OF PAGE]

  449. Concentration of coliphages from large volumes of water and waste water. Goyal,S.M., Zerda,K.S., Gerba,C.P. (1980). Appl. Environ. Microbiol. 39:85-91. An evaluation was made of the positively charged filters used for concentrating coliphages from sewage and tap water, and they were compared with negatively charged filters. Four different coliphages were studied. Positively charged microporous filters were found to efficiently adsorb these coliphages from tap water, sewage, and lake water at neutral pH. Adsorbed viruses were eluted with a 1:1 mixture of 8% beef extract and 1 M sodium chloride at pH 9. Using this method, coliphages could be concentrated from 17-liter volumes of tap water with recoveries ranging from 34 to 100%. Coliphages occurring naturally in raw and secondarily treated sewage were recovered with average efficiencies of 56.5 and 55.0%, respectively. This method should be useful in isolating rare phages, studying the ecology of phages in natural waters, and evaluating water quality. [TOP OF PAGE]

  450. Microbiological Investigations in Indian Coastal Waters and the Indian Ocean. Iyer,K.M., Pillai,V.K. (1980). J. Marine Biol. Assoc. India 18:266-271. The past two decades have witnessed several marine microbiological investigations being carried out by different workers on the east and west coasts of India. The enumeration of the heterotrophic bacteria of the surface and bottom waters, muds and plankton tows and of certain physiological groups had been carried out off the coast of Madras, in the Palk Bay and the Gulf of Mannar. The nature of the bacterial flora associated with sea water and fishes off Malabar Coast had also been worked out though less exhaustively. The quantitative as well as the generic distribution of bacteria in sea water off Cochin and in fresh fishes caught therein has recently been studies. Marine bacteria producing B12 and certain antibiotics had been isolated from the sea water and marine muds off Bombay Coast. Investigation on marine yeasts was first done in Bombay waters and subsequently studies were made in Vellar Esturary and the near-shore waters of Porto Novo. The distribution of yeasts in the Indian Ocean has been studied recently during the International Indian Ocean Expedition. The occurrence of marine bacteriophages had been reported earlier at Bombay and the recent International Indian Ocean Expedition has met with bacteriophages in the bottom and off East African Coast. [TOP OF PAGE]

  451. HOST RANGE PLAQUE MORPHOLOGY STUDIES OF CYANO PHAGE LPP-1. KRAUS,M.P. (1980). J. Phycol. 16:186-191. Host-range, plaque-morphology studies of cyanophage LPP-1.Transduction by temperate cyanophage plays an important role in understanding the effects of environmental pollution on genetic function. Using a new isolate, the influence of contaminants and the rapid variations that result as a virus particle passes through successive hosts is illustrated. Host-range and plaque-morphology, using an extended range of genetically-differing hosts, compares archetype LPP-1 cyanophage cultured on microbially contaminated hosts with bacteria-free cyanophage cultured on pure host strains. Microbial contamination can alter the host-range and serology of the cyanophage produced. Bacteria are involved in the virus infection of cyanophycean hosts and the study of host-range and plaque-morphology can aid in the biological characterization and segregation of mutants illustrating mechanisms of intergeneric transfer of genetic material. Derivatives of archetype LPP-1, cultured on axenic hosts, possess a host-range, plaque-morphology and serology similar or identical to that of the temperate cyanophage, S3. [TOP OF PAGE]

  452. A method of detection of bacteriophages from ocean water. Moebus,K. (1980). Helgol. Meeresunters. 34:1-14. A method for the isolation of bacteriophages from ocean water is described. It precludes sample storage before starting phage-enrichment cultures and provides for the use of 3 sub-samples enriched with organic nutrients after 1, 2 and 3 days of incubation. The method was used with samples collected from 6 m below the surface at 48 stations between the European continental shelf and the Sargasso Sea. With 213 among 931 bacterial isolates about 250 strains of bacteriophages were detected by two methods of different sensitivity. [TOP OF PAGE]

  453. Incidence of marine bdellovibrios lytic against Vibrio parahaemolyticus in Chesapeake Bay. Williams,H.N., Falkler,W.J., Shay,D.E. (1980). Appl. Environ. Microbiol. 40:970-972. The incidence of marine bdellovibrios at selected sampling sites in the Chesapeake Bay during the months of June 1978 and 1979 was studied. Bdellovibrios were isolated from eight of nine sampling stations in the bay. Higher numbers than previously reported with sea or ocean water were recovered in the midregion of the bay. [TOP OF PAGE]

  454. Photoreactivation of ultraviolet irradiated blue-green alga: Anacystis nidulans and cyanophage AS-1. Amla,D.V. (1979). Arch Virol 59:173-179. Ultraviolet (UV) inactivation and photoreactivation of Anacystis nidulans and cyanophage AS-1 was studied at different wavelengths. UV inactivation of free phage particles and one and two hour host-phage complexes (intracellular phages) were exponential. UV resistance of plaque forming units was attained at the latter phase of latent period. Black, blue and white lights were able to photoreactivate the UV irradiated A. nidulans whereas green, yellow and red lights were not. However, incubation of A. nidulans for more than 2 hours in black light resulted in loss of viability but shift to red light caused significant recovery. This suggests the involvement of two types of photoreactivation, i.e. of photoenzymatic repair of DNA and of the repair of the photosynthetic apparatus of A. nidulans. [TOP OF PAGE]

  455. EXPERIMENTAL CONTAMINATION OF OYSTERS BY BACTERIO PHAGES. Attree-Pietri,C., Aubert,J. (1979). Revue Internationale dOceanographie Medicale 53-54:71-76. Experimental contamination of oysters by bacteriophages.Oysters were contaminated during a 5 day period by 3 bacteriophages : P22, T4 and Twort. No concentration phenomenon appeared during the time of the study. There was only a more or less rapid contamination of the organisms depending of the nature of the bacteriophage. No decrease of the level of the bacteriophages was observed in the incubation medium. The bacteriophage level in the homogenates of oysters is at most equal to the level in the incubation medium. [Bacteriophage assays may be useful in monitoring bacterial contamination of marine products to be used for human consumption]. [TOP OF PAGE]

  456. Differential toxicities of mercury to bacteria and bacteriophages in sea and in lake water. Babich,H., Stotzky,G. (1979). Can. J. Microbiol. 25:1252-1257. Mixtures of anionic HgCl3- /HgCl42- complexes were less toxic to terrestrial bacteria (Erwinia herbicola, Agrobacterium tumefaciens) , to marine bacteria (Acinetobacter sp., Aeromonas sp.), and to phages ( 11M15 of Staphylococcus aureus and P1 of Escherichia coli ) than were equivalent concentrations of Hg as cationic HgSUP-2+ . The toxicity of 1 p.p.m.-Hg to A. tumefaciens, Aeromonas sp., and 11M15 was less in seawater than in lake water. Inasmuch as the Hg-Cl species are formed in environments of high chloride concentration, it was postulated that the lower toxicity of Hg in seawater was a result of the formation of HgClSUB-3 SUP-- /HgClSUB-4 SUP-2- complexes. [TOP OF PAGE]

  457. Virus infection affects the molecular properties and activity of glucose-6-P dehydrogenase in Anacystis nidulans, a Cyanobacterium. Novel aspect of metabolic control in a phage-infected cell. Balogh,A., Borbely,G., Cseke,C., Udvardy,J., Farkas,G.L. (1979). FEBS Lett. 105:158-162. [TOP OF PAGE]

  458. Effect of light on the attachment of cyanophage AS-1 to Anacystis nidulans. Cseke,C.S., Farkas,G.L. (1979). J. Bacteriol. 137:667-669. The effect of illumination on the extent and kinetics of the adsorption of cyanophage AS-1 to the blue-green alga (cyanobacterium) Anacystis nidulans was studied by using 32P-labeled phage. The initial rate of adsorption was not significantly affected by light. However, at Na+ levels used ordinarily to culture the alga ([Na+] = 11.7 mM), the total amount of phage adsorbed was doubled in the illuminated cultures, as compared with the dark-grown ones, over a wide range of multiplicities of infection (0.05 to 20). Upon a 10-fold increase in Na+ concentration in the medium ([Na+] = 0.11 M), the dark adsorption of the phage increased to the level of light adsorption found in low Na+ medium. The effects on phage adsorption of high Na+ concentration and light were not additive. [TOP OF PAGE]

  459. Characteristics of Anabaena variabilis influencing plaque formation by cyanophage N-1. Currier,T.C., Wolk,C.P. (1979). J. Bacteriol. 139:88-92. Phage N-1 grown in Anabaena strain 7120 [N-1 . 7120] forms plaques on A. variabilis about 10(-7) to 10(-6) as efficiently as on Anabaena 7120. By manipulating different characteristics of the interaction between phage and host, it was possible to increase the relative efficiency of plaque formation to 0.38. Growth of A. variabilis at 40 degrees C for at least three generations resulted in an increase in the rate of phage adsorption and a 10-fold increase in the efficiency of plaque formation. The efficiency of plaque formation was further increased about 42-fold, with little or no further increase in rate of adsorption, in a variant strain. A. variabilis strain FD, isolated from a culture of A. variabilis which had grown for more than 30 generations at 40 degrees C. The low relative efficiency of plaque formation by N-1 . 7120 on A. variabilis could be partially accounted for if A. variabilis contains a deoxyribonucleic acid restriction endonuclease which is absent from Anabaena 7120. Indirect evidence for such an endonuclease included the following: (i) phage N-1 grown in A. variabilis (N-1 . Av) had approximately a 7 X 10(3)-fold higher relative efficiency of plaque formation on A. variabilis than had N-1 . 7120; and (ii) the efficiency of plaque formation by N-1 . 7120 on A. variabilis strain FD was increased by up to 146-fold after heating the latter organism at 51 degrees C. [TOP OF PAGE]

  460. Viruses of marine algae. Dodds,J.A. (1979). Experimentia 35:440-442. [TOP OF PAGE]

  461. Lytic organisms and photooxidative effects: Influence of blue-green algae (cyanobacteria) in Lake Mendota, Wisconsin. Fallon,R.D., Brock,T.D. (1979). Appl. Environ. Microbiol. 38:499-505. [TOP OF PAGE]

  462. A virus which lyses the marine nanoflagellate Miromonas pusilla. Mayer,J.A., Taylor,F.J.R. (1979). Nature 281:299-301. [TOP OF PAGE]

  463. Optimization kinetics and thermodynamics of cyanophage A-1 adsorption on algal cells. Mendzhul,M.I. (1979). Mikrobiol. Zh. 41:145-150. Optimization, kinetics and thermodynamics of cyanophage A-1 adsorption on algal cells.The extremely rapid adsorption of cyanophage A-1 on the alga Anabaena variabilis cells occurs in 0.01 M tris-HCl-buffer in the presence of 0.1 M MgCl2 at pH 7.0 and C. Kinetics of the cyanophage adsorption on the host cells is more complex than the 1st order reaction. Analysis of kinetic curves for the cyanophage adsorption and some other characteristics of the process showed that cyanophage A-1 adsorption on the cells occurred according to the competition model. Some thermodynamic potentials of the process are calculated; their values indicate an enzymic character of the reaction of the virion attachment to the algal cell. [TOP OF PAGE]

  464. [Effect of the detergent Metaupon on replication of various phages]. Menzel,G., Stenz,E. (1979). Z Allg Mikrobiol 19:325-332. As several other surfactants do, the detergent Metaupon acts on the multiplication of bacteriophages. We investigated the influence of Metaupon on the phages phi and lambda, the cyanophage LPP-1, and the RNA-phages f 2, M 12, and Q beta by means of the agar diffusion test, pour plate test, adsorption test, and one-step growth test. The action of Metaupon on the free phages was also tested. Metaupon inhibits the formation of plaques by the phages with exception of lambda. With the phages f 2 and M 12 the substance increases the amount of plaques depending on concentration. The main mode of action of Metaupon was found to be the inhibition of the adsorption of the phages to the host cells. Only in the case of phi 105 free phages were inactivated. [TOP OF PAGE]

  465. Lysate effect of Microcystis aeruginosa infected with cyanophage AM-1 on survival of Daphnia magna. Myslovich,V.O. (1979). Gidrobiologicheskii Zhurnal 15:67-70. Lysate effect of Microcystis aeruginosa infected with cyanophage AM-1 on survival of Daphnia magna.The behavior and survival of Daphnia magna juvenile influenced by lysates of Microcystis aeruginosa Keutz. emend. Elenk. culture infected by cyanophage AM-1 depend on dilution level and storage time of the lysates. Toxic effects are possible under natural conditions when lysis of cyanophage AM-1-infected algae occurs. [TOP OF PAGE]

  466. An ultraviolet light induced bacteriophage in Beneckea gazogenes. Rambler,M., Margulis,L. (1979). Origins of Life 9:235-240. An ultraviolet light induced prophage has been discovered in the red pigmented marine vibrio Beneckea gazogenes. Two spontaneously derived pigment mutants, one forming pink colonies and one lacking pigment and forming white colonies, were also irradiated. The presence of pigment was not related to phage induction; uv-induced cell lysis occurred in wildtype and mutant strains at the same dosages. Lysis was not prevented or retarded by exposure after irradiation to visible light indicating the phenomenon was not photoreactivable. Electron micrographs of the 'T-like' B. gazogenes phage are shown. A second beneckea was isolated form the anaerobic zone of cyanobacterial mats growing in the hypersaline environment of Laguna Mormona, Baja California. The Baja beneckea does not harbor a uv inducible prophage and is resistant to the B. gazogenes phage under all conditions tested. [TOP OF PAGE]

  467. The Practical Directory to the Phycovirus Literature. Safferman,R.S., Rohr,M.E. (1979). EPA-600/9-79-013. Cincinnati, Ohio, U.S. Environmental Protection Agency. The volume comprises a comprehensive survey of the phycovirus literature. It covers the period from their isolation to the present time. [TOP OF PAGE]

  468. Incidence of Vibrio parahaemolyticus bacteriophages and other Vibrio bacteriophages in marine samples. Baross,J.A., Liston,J., Morita,R.Y. (1978). Appl. Environ. Microbiol. 36:492-499. Vibrio bacteriophages were isolated by enrichment from 177 of 643 samples of marine molluscan shellfish, crustaceans, seawater, and sediments. The predominant bacteriophage types isolated were specific for some strains of Vibrio parahaemolyticus. A high frequency of phage isolations was also observed with strains of agar-digesting vibrios (21 of 56) and psychrophilic vibrios (14 of 72) that were originally isolated from non-shellfish growing areas. No bacteriophages were isolated against V. alginolyticus and only rarely for V. anguillarum even though these were the two most abundant species found in near-shore environments. No V. cholerae phages were isolated. It was also determined from quantitative studies on the Pacific oyster (Crassostrea gigas) obtained from two environments in Washington and Oregon that the titers of V. parahaemolyticus bacteriophages increased with increasing seasonal water temperatures and that this was proportional to the increase in numbers of mesophilic vibrios and not with the incidence of V. parahaemolyticus. Titers of V. parahaemolyticus bacteriophages occasionally exceeded lo6 per g of oyster during the summer months. Specific V. parahaemolyticus bacteriophages were also isolated from market seafoods and other marine samples that originated in cold environments where no mesophilic vibrios are expected to be found. The possibility that V. parahaemolyticus bacteriophages originate from Vibrio spp. other than V. parahaemolyticus and the role of these bacteriophages in the ecology of marine vibrios are discussed. [TOP OF PAGE]

  469. Ecological relationship between Vibrio parahaemolyticus and agar-digesting vibrios as evidenced by bacteriophage susceptibility patterns. Baross,J.A., Liston,J., Morita,R.Y. (1978). Appl. Environ. Microbiol. 36:500-505. Twenty bacteriophages active against Vibrio parahaemolyticus and agar-digesting vibrios, isolated from oysters (Crassostrea gigas) and Dungeness crab (Cancer magister) and by induction of a lysogenic agar digester, were tested as to their host range. These phages were specific for V. parahaemolyticus and various agar-digesting vibrios, and interspecies lysis occurred only between these two groups. V. alginolyticus, V. anguillarum and related species, V. cholerae, and a group of marine psychrophilic and psychrotrophic vibrios were not affected. No correlation was observed between the O and K serotypes of V. parahaemolyticus strains and bacteriophage susceptibility patterns, and 7 of 28 strains of V. parahaemolyticus were not lysed by any of the phages. Only two of the phage isolates were capable of lysing all susceptible V. parahaemolyticus strains. No correlation was observed between the inter-and intraspecies genetic relatedness (DNA homologies) of V. parahaemolyticus and agar-digesting vibrios and susceptibility patterns to different bacteriophages. Some of the phages were capable of plaque formation on V. parahaemolyticus as well as on some strains of agar-digesting vibrios that were separated by 70 to 80% differences in their DNA homologies. The possible ecological significance of these vibrio bacteriophages, particularly those having a wide host range, is discussed. [TOP OF PAGE]

  470. Phage-algal interactions in the cyanophage AS-1/blue-green alga Anacystis nidulans infective system. Blashka,K.H. (1978). City University of New York. [TOP OF PAGE]

  471. Kinetics mechanism and thermodynamics of cyanophage A-1 adsorption on the cells of algae-host. Bobrovnik,S.A., Mendzhul,M.I., Lysenko,T.G. (1978). Biofizika 23:489-493. [TOP OF PAGE]

  472. Cytological studies on a new species of rickettsia found in association with a phage in the digestive gland of the marine bivalve mollusc, Tellina tenuis (da Costa). Buchanan,J.S. (1978). J. Fish Dis. 1:27-43. The secretory cells of the digestive glands of up to 75% of Tellina tenuis from sheltered sandy beaches on the Scottish coast contained intracytoplasmic inclusion bodies consisting of microcolonies of a rickettsia-like organism. The development and morphology of these parasitic bacteria and the cytopathic effect on the host cells are described. These features closely resemble those of the genus Coxiella of the family Rickettsiaceae. It was possible to culture the organism in embryonated hens' eggs. Scattered particles and paracrystalline arrays of a virus were seen in association with the bacteria. This is believed to be the first description of a phage from a rickettsia. [TOP OF PAGE]

  473. Viral Control of blue-green algae. Desjardins,P.R., Barkley,M.B., Swiecki,S.A., West,S.N. (1978). California Water Resource Center, University of California, [TOP OF PAGE]

  474. Antibacterial activity of seawater and microvibrion-predators (Microvibrio marinus Roscoffensis) in it. Gelen,A.M., Mishustina,I.E., Gulevskaya,S.A., Pechnikov,N.V., Ledova,L.A. (1978). Biology Bulletin of the Academy of Sciences of the USSR 5:690-695. In the seawater of the Atlantic Ocean and surface waters of different points of the World Ocean, including arctic basins and equatorial regions, microvibrion-predators of bacterial cells have been discovered. The number of microvibrions in the surface waters of the English Channel reaches a thousand cells per ml, but it varies, depending on the season. In this article a method of the separation and culture of microvibrions is described. The ultrastructure of two strains of microvibrions was investigated and a similarity found between their structure and Gram-negative bacteria. The distinctive features of microvibrions are their sea derivation and the ability to reproduce only in the presence of bacteria, without penetrating bacterial cells. To a certain extent, the antibacterial activity of seawater is connected with the presence in it of microvibrions. [TOP OF PAGE]

  475. Some problems of the ecology and taxonomy of marine microvibrios. Guelin,A.M., Mishustina,I.E., Andreev,L.V., Bobyk,M.A., Lambina,V.A. (1978). Biology Bulletin of the Academy of Sciences of the USSR 5:336-340. The bactericidal effect of water from the Indian and Pacific oceans and Caspian and White seas on Escherichia coli was studied. It is shown that a decrease in the viability of E. coli cells is accompanied by the appearance and active multiplication of small bacteria of a vibrioid form. Two strains of such bacteria were isolated from a suspension of E. coli in seawater and purified from membranes of the substrate organism by the method of centrifugation in a Ficoll gradient. The marine bacteria of vibrioid form are very similar to the bacterial parasite Bdellovibrio bacteriovorus in fatty acid composition and characteristic cycle of development. [TOP OF PAGE]

  476. Cyanophages S-2L contains DNA with 2,6-diaminopurine substituted for adenine. Khudyakov,I.Y., Kirnos,M.D., Alexandrushkina,N.I., Vanyushin,B.F. (1978). Virology 88:8-18. [TOP OF PAGE]

  477. Effect of virazole (ribavirin) on virus-prokaryote systsems. Menzel,G., Stenz,E. (1978). Acta Microbiol. Acad. Sci. Hungary 25:11-15. [TOP OF PAGE]

  478. Effects of host aging, ions, and pH on the adsorption of the cyanovirus N-1 to Nostoc muscorum. Padhy,R.N., Singh,P.K. (1978). Arch. Microbiol. 116:289-292. [TOP OF PAGE]

  479. Lysogeny in the blue-green alga Nostoc muscorum. Padhy,R.N., Singh,P.K. (1978). Arch. Microbiol. -265 268. [TOP OF PAGE]

  480. Reversion of virus N-1 resistant mutant ofthe blue-green alga Nostoc muscorum. Padhy,R.N., Singh,P.K. (1978). Experientia 34:1565 [TOP OF PAGE]

  481. Stabilizing effects of metallic ions in the blue-green algal virus N-1. Padhy,R.N., Singh,P.K. (1978). Biochem. Physiol. Pflanz. 173:188-192. [TOP OF PAGE]

  482. Adsorption of cyanophage AS-1 to unicellular cyanobacteria and isolation of receptor material from Anacystis nidulans. Samimi,B., Drews,G. (1978). J. Virol. 25:164-174. [TOP OF PAGE]

  483. Cyanophages and viruses of eukaryotic algae. Sherman,L.A., Brown,R.M. (1978). pp. 145-234. In In Fraenkel-Conrat,H. and Wagner,R.R. (eds.), Comprehensive Virology. Plenum Press, New York. [TOP OF PAGE]

  484. Manganese toxicity and mutagenesis in two blue-green algae. Singh,S.P., Kashyap,A.K. (1978). Environmental and Experimental Botany 18:47-53. [TOP OF PAGE]

  485. [Effect of 1,3,5-triazines on several prokaryote viruses and their hosts]. Stenz,E., Menzel,G. (1978). Zeitsch. Allg. Mikrobiol. 34:748-753. In the agar diffusion test 24 triazines were investigated with regard to their action on the mulplication of DNA phages (lambda and LPP-1) and RNA phages (M12 and Qbeta). In several cases the amount of plaques was diminished or increased depending on the kind of triazine and virus. The investigations demonstrate the triazines to be able to interfere with the formation of plaques by virulent and temperate viruses of procaryotes. [TOP OF PAGE]

  486. Effect of photosynthesis and respiration on growth of cyanophages of Anabaena variabilis. Al-Musavi,R.A. (1977). Mikcrobiologiya 46:725-729. [TOP OF PAGE]

  487. Coliphages in sewage and the marine environment. Ayres,P.A. (1977). pp. 275-298. In In Skinner,F.A. and Shewan,J.M. (eds.), Aquatic Microbiology. Academy Press, New York, New York. [no abstract]. [TOP OF PAGE]

  488. Simple, effective method for purifying the AS-1 cyanophage. Barkley,M.B., Desjardins,P.R. (1977). Appl. Environ. Microbiol. 33:971-974. [TOP OF PAGE]

  489. Inhibition of lytic induction in lysogenic cyanophyces. Cocito,C., Goldstein,D. (1977). J. Virol. 23:483-491. [TOP OF PAGE]

  490. [Study of marine microvibrios of Roscoff (Microvibrio marinus roscoffensis)]. Guelin,A., Michoustina,I.E., Goulevskaya,S.A., Petchnikov,N.V., Ledova,L.A. (1977). COMPTES RENDUS HEBDOMADAIRES DES SEANCES DE L ACADEMIE DES SCIENCES. 284:2171-2174. Marine microvibrios, predators of E. coli, have been detected worldwide, from equatorial waters to the polar regions. The morphology and behavior of two microvibrios have been studied. Their multiplication and aggressiveness in regard to their bacterial prevy are not impeded by dialysis membranes and manifest themselves, away from all direct contact between the predator and its prey. [TOP OF PAGE]

  491. Detection and isolation of marine bacteriophage systems in the Southwestern part of the Pacific Ocean. Hidaka,T. (1977). Mem. Fac. Fish. Kagoshima Univ. 26:55-62. [TOP OF PAGE]

  492. Studies on the natural relationships of cyanophages and their hosts and the nature of resistance. Jenifer,F.G. (1977). New Brunswick, N.J., Comple.Rep.Water Resour.Res.Inst. [TOP OF PAGE]

  493. Chemical and biological studies on the lipopolysaccharide (O-antigen) of Anacystis nidulans. Katz,A., Weckesser,J., Drews,G., Mayer,H. (1977). Arch. Microbiol. 113:247-256. [TOP OF PAGE]

  494. 2,6-Diaminopurine—a new adenine substituting base in DNA of cyanophage S-2. Khudyakov,I.Y., Kirnos,M.D., Aleksandrushkina,N.I., Vanyushin,B.F. (1977). Doklady Akademii Nauk SSSR 232:965-968. [TOP OF PAGE]

  495. Characteristics of a new cyanophage S-2L lysing the unicellular cyanobacterium belonging to the Synechococcus genus. Khudyakov,I.Y. (1977). Mikrobiologija (Microbiologiia) ???:904-907. [TOP OF PAGE]

  496. 2-Aminoadenine is an adenine substituting for a base in S-2L cyanophage DNA. Kirnos,M.D., Khudyakov,I.Y., Alexandrushkina,N.I., Vanyushin,B.F. (1977). Nature 270:369-370. [TOP OF PAGE]

  497. Cyanophages of series A (L), specific for blue-green algae Anabaena variabilis. Koz'yakov,S.Y. (1977). pp. 151-171. In In Gromov,B.V. (ed.), Experimental Algology. Biolog.Sci.Res.Inst., Leningrad State University, [TOP OF PAGE]

  498. Effect of pH and EDTA on multiplication of blue-green algal virus. Padhy,R.N., Singh,P.K. (1977). Microbios Letters 5:135-139. [TOP OF PAGE]

  499. Effect of physical and chemical agents on the blue-green algal virus N-1. Padhy,R.N., Singh,P.K. (1977). Acta Virol. 21:264-267. [TOP OF PAGE]

  500. Effect of temperature on the adsorption and one-step growth of the Nostoc virus N-1. Padhy,R.N., Singh,P.K. (1977). Archives of Microbiology 115:163-167. This study was an attempt to observe the effects of temperature on adsorption and one-step growth of the virus N-1 infecting the nitrogen-fixing cyanobacterium Nostoc muscorum. Adsorption rate was found to maximum at 40 degrees C whereas no adsorption occurred at 10 degrees C. The Q10 value was about 2.03 and the energy of activation, Ea was 16.3 kcal/mole for the adsorption process. The development cycle of the virus was temperature sensitive. With increase in temperature, a gradual increase in inhibition of virus yield i.e. 8.33% at 30 degrees C, 35.3% at 35 degrees C and complete inhibition at 40 degrees C was observed. Out of 7 h latent period, the early 4 h were temperature sensitive and heat treatment had a reversible inhibitory effect on virus development. The temperature treatment did not affect the rise period but burst-size was reduced. [TOP OF PAGE]

  501. Effects of cyanophage SAM-1 upon Microcystis aeruginosa. Parker,D.L., Jansen,G.P., Corbett,L. (1977). EPA-600/3-77-079. Corvallis, Orgegon, Evironmental Research Laboratory. [TOP OF PAGE]

  502. Cyanophage AC-1 infecting the blue green alga Anacystis nidulans. Sharma,C.R., Venkataraman,G.S., Prakash,N. (1977). Curr. Sci. 46:496-497. A new phage type infecting A.nidulans 14011 and Chroococcus minor ARM was isolated from a waste stabilization pond in New Delhi. The phage formed clear plaques of 4-6 min after 10 days incubation. Several blue-green algal species of Nostoc, Anabaena, T.lypolthrix, Aulosira and Spirulina, the green alga Chlorella vulgaris, and the bacteria Azotobacter chroococcum, Rhizobium spp and Rhodopseudomonas capsulata were also tested for susceptibility to this phage, but none were susceptible. The short non-contractile tail of this AC-1 phage differentiated it from AS-1 and is similar to SM-1. [TOP OF PAGE]

  503. Assembly site of cyanophage LPP-2-SPI in Plectonema boryanum. Silverberg,J., Rimon,A., Kessel,M., Oppenheim,A.B. (1977). Virology 77:437-440. [TOP OF PAGE]

  504. Induction of mutations in the blue-green alga Plectonema boryanum. Singh,R.N., Kashyap,A.K. (1977). Mut. Res. 43:37-44. [TOP OF PAGE]

  505. Isolation and characterization of temperature sensitive mutants of cyanophage LPP-1. Singh,R.N., Kashyap,A.K. (1977). Mol. Gen. Genet. 154:31-34. [TOP OF PAGE]

  506. Cyanophage as an Indicator of Animal Viruses in Wastewater. Stagg,C.H., Gerba,C.P. (1977). Journal / Water Pollution Control Federation 49:1915-1916. [TOP OF PAGE]

  507. Serological typing and chlorination resistance of wastewater cyanophages. Stanley,J.L., Cannon,R.E. (1977). J. Water Pollut. Control Fed. 49:1993-1999. [TOP OF PAGE]

  508. Microbial pathogens of cyanophycean blooms. Stewart,W.D.P., Daft,M. (1977). pp. 177-218. In In Droop,M.R. and Jannasch,H.W. (eds.), Advances in Aquatic Microbiology. Volume 1. Academic Press, New York. [TOP OF PAGE]

  509. Effect of some environmental factors on cyanophage AS-1 development in Anacystis nidulans. Allen,M.M., Hutchison,F. (1976). Archives of Microbiology 110:55-60. The development cycle of the cyanophage AS-1 was studied in the host blue-green alga, Anacystis nidulans, under conditions that impair photosynthesis and under various light/dark regimes. Under standard conditions of incubation the 16-h development cycle consisted of a 5-h eclipse period and an 8-h latent period. Burst size was decreased by dark incubation to 2% of that observed in the light. An inhibitor of photosystem II, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU), reduced the burst size to 27% of that of the uninhibited control, whereas cyanophage production was completely abolished by carbonyl-cyanide m-chlorophenyl hydrazone (CCCP), an inhibitor of photosynthetic electron transport. Dark incubation of infected cells decreased the latent period by 1-2 h and the eclipse period by 1 h, once the cultures were illuminated. This suggests that adsorption took place in the dark. Intracellular growth curves indicated that light is necessary for viral development. Infected cells must be illuminated at least 13 h to produce a complete burst at the same rate as the continuously illuminated control. Low light intensities retarded the development cycle, and at lowest light intensities no phage yield was obtained. AS-1 is highly dependent on host cell photophosphorylation for its development. [TOP OF PAGE]

  510. Genetics of cyanophyceae and cyanophages. Amla,D.V. (1976). Banaras Hindu University. [TOP OF PAGE]

  511. Ultraviolet light inactivation and photoreactivation of AS-1 cyanophage in Anacystitis nidulans. Asato,Y. (1976). J. Bacteriol. 126:550-552. [TOP OF PAGE]

  512. Ultrastructure of the blue-green algae Anacystis nidulans infected with AS-1 virus. Barkley,M.B. (1976). University of California, Riverside. [TOP OF PAGE]

  513. The??? Post-maturation cleavage of 23S ribosomal-RNA in Anacystis nidulans is inhibited by infection with cyanphage AS-1. Borbely,G., Kolcsei,M., Farkas,G.L. (1976). Molec. Biol. Rpts. 3:139-142. [TOP OF PAGE]

  514. Interaction of Plectonema boryanum (Cyanophyceae) and the LPP cyanophages in continuous culture. Cannon,R.E., Shane,M.S., Whitaker,J.M. (1976). J. Phycol. 12:418-421. [TOP OF PAGE]

  515. Induction of a lytic cycle in lysogenic cyanophyces. Cocito,C., Coucau,B., Goldstein,D. (1976). pp. 657-662. In AnonymousNucleic Acids and Protein Synthesis in Plants. Strasbourg, France. [TOP OF PAGE]

  516. Genetics of blue-green algae. Delaney,S.F., Herdman,M., Carr,N.G. (1976). pp. 15-16. In In Lewin,R.A. (ed.), The Genetics of Algae. University of California Press, Berkeley. [TOP OF PAGE]

  517. Cyanophage SM-2: A new blue-green algal virus. Fox,J.A., Booth,S.J., Martin,E.L. (1976). Virology 73:557-560. [TOP OF PAGE]

  518. Metabolic aspects of LPP cyanophage replication in the cyanobacterium Plectonema boryanum. Ginzberg,D., Padan,E., Shilo,M. (1976). Biochim. Biophys. Acta 423:440-449. Cyanophage LPP1G is reproduced at the same yield in heterotrophic conditions (dark, glucose) as in photoautotrophic conditions; aerobiosis is required for dark cyanophage replication. Exogenous glucose is not required for the cyanophage replication in the dark in heterotrophically grown cells. In photoautotrophically grown cells, the maximum burst size in dark and glucose is delayed for a period corresponding to glucose uptake induction. Cyanophage LPP2SPI replication occurs in conditions where only Photosystem I operates. Of photosynthesis parameters tested, only CO2 photoassimilation is affected during cyanophage LPP1G infection under photoautotrophic conditions. [TOP OF PAGE]

  519. Lysogeny in unicellular blue-green algae. Goryushin,V.A., Shatokhina,E.S., Grigoreva,G.A., Shestakov,S.V. (1976). Vestn. Mosk. Univ. ,Ser. VI, Biol. Pochvoved. 31:82-84. [TOP OF PAGE]

  520. Microorganisms-Algal Parasites. Gromov,B.V. (1976). Univesity of Leningrad Publishing, Leningrad.[TOP OF PAGE]

  521. Cyanobacterial DNA-binding protein related to Escherichia coli HU. Haselkorn,R., Rouviere-Yaniv,J. (1976). Proc. Natl. Acad. Sci. USA 73:1917-1920. [TOP OF PAGE]

  522. Properties of a marine RNA-containing bacteriophage. Hidaka,T., Ichida,K. (1976). Mem. Fac. Fish. Kogoshima Univ. 25:77-89. [TOP OF PAGE]

  523. S-2, a new virus of unicellular cyanobacteria. McMillan,J.A. (1976). Univesity of Wisconsin. [TOP OF PAGE]

  524. Isolation of a small rod with lytic activity against Vibrio parahaemolyticus from fresh sea water. Myamoto,S., Kuroda,K., Hanaoka,M., Okada,Y. (1976). Jap. J. Microbiol. 20:517-527. A small rod, capable of formine crater-like plaques on lawns of Vibrio parahaemolyticus, was isolated from a marine environment. The isolate was a gram-negative straight rod with round ends and was small in size, equal to that of halophilic Bdellovibrio strain 5501. The isolate appeared to have close taxonomic relationships to Cytophaga, since this bacterium moved slowly in a gliding manner on a solid agar surface, hydrolyzed agar and starch, contained yellow pigment and was halophilic. The isolate was able to grow not only under host-dependent but also under host-independent conditions when low nutrient media were used for cultivation, and its bacteriolytic mode was different from that of Bdellovibrio, an endoparasite. The isolate was halophilic and required Mg++ and Ca++ in addition to 3% saline for growth. The isolate showed a broad host rnage when tested for plaque-forming activity on gram-negative bacteria but not on the gram-positive bacteria tested so far. [TOP OF PAGE]

  525. The use of cellulose products to reduce agar concentration in microbiological media. Myrvik,A.L., Whitaker,J.M., Cannon,R.E. (1976). Can. J. Microbiol. 22:1002-1006. The use of agar in media for culturing microorganisms is fundamental to microbiological investigations. Shortages of agar have caused increased costs and difficulty in obtaining media. Evidence is presented for the use of carboxymethylcellulose (CMC), an inert compound, in conjunction with agar to reduce the concentration of agar necessary to achieve a solid plating surface. A variety of bacteria, blue-green bacteria, fungi, and a yeast were tested for growth on CMC agar media. T-2 bacteriophage and three cyanophages were tested for plaque-forming efficiency on CMC agar plates. Selective and differential media were also formulated with a CMC agar supplement. Growth of all microorganisms was comparable on CMC and agar control. Use of cellulose products provides a means of decreasing agar consumption without affecting successful cultivation of microorganisms. [TOP OF PAGE]

  526. Mutation to resistance for virus N-1 in the blue-green alga Nostoc muscorum. Padhy,R.N., Singh,P.K. (1976). Arch. Virol. 52:85-90. [TOP OF PAGE]

  527. Reactivation of ultraviolet irradiated cyanophage AS-1 in cells of the blue-green alga Anacystis nidulans. Polukhina,L.E., Karbysheva,E.A., Shestakova,S.V. (1976). Vestn. Mosk. Univ. ,Ser. VI, Biol. Pochvoved. 31:30-33. [TOP OF PAGE]

  528. Heterotrophic capacities of Plectonema boryanum. Raboy,B., Padan,E., Shilo,M. (1976). Arch. Microbiol. 110:77-85. [TOP OF PAGE]

  529. Protein synthesis following infection of the blue-green alga Plectonema boryanum with the temperate virus SPI and its ts mutants. Rimon,A., Oppenheim,A.B. (1976). Virology 71:444-452. [TOP OF PAGE]

  530. Assessment of virus removal by a multistage activated sludge process. Safferman,R.S., Morris,M.E. (1976). Water Res. 10:413-420. [TOP OF PAGE]

  531. Blue-green algae and cyanophages as a model in molecular biology. Satava,J. (1976). Biol. Listy 41:121-124. [TOP OF PAGE]

  532. Infection of Synochecoccus cedrorum by the cyanophage AS-1M. III. Cellular metabolism and phage development. Sherman,L.A. (1976). Virology 71:199-206. [TOP OF PAGE]

  533. Infection of Synechococcus cedrorum by the cyanophage AS-1M. I. Ultrastructure of infection and phage assembly. Sherman,L.A., Connelly,M., Sherman,D.M. (1976). Virology 71:1-16. [TOP OF PAGE]

  534. Infection of Synechococcus cedrorun by the cyanophage AS-IM. II. Protein and DNA synthesis. Sherman,L.A., Pauw,P. (1976). Virology 71:17-27. [TOP OF PAGE]

  535. Isolation and characterization of a cyanophage infecting the unicellular blue-green algae. Sherman,L.A., Connelly,M. (1976). Virology 72:540-554. [TOP OF PAGE]

  536. The genetics of cyanophyceae and cyanophages: problems and prospects. Singh,R.N., Chaubev,I.J. (1976). J. Cytol. Genet. 11:116-121. [TOP OF PAGE]

  537. Mutagenesis in cyanophage LPP-1. Singh,R.N., Kashyap,A.K. (1976). Mut. Res. 37:19-25. [TOP OF PAGE]

  538. Effect of infection with cyanophage AM-1 on the metabolism of the blue-green alga. Sirenko,L.A., Myslovich,V.O., Goryushin,V.A., Mikhailyuk,D.P. (1976). Fiziol. Rast. 23:1214-1218. [TOP OF PAGE]

  539. Cyanophage analysis as a biological pollution indicator--bacteria and viral. Smedberg,C.T., Cannon,R.E. (1976). Journal / Water Pollution Control Federation 48:2416-??? [TOP OF PAGE]

  540. Algal lysing agents of freshwater habitats. Stewart,W.D.P., Daft,M.J. (1976). pp. 63-90. In In Skinner,F.A. and Carr,J.G. (eds.), Microbiology in Agriculture, Fisheries and Food, Symposium Series #4. Academic Press, New York. [TOP OF PAGE]

  541. Formation in the dark of virus-induced deoxyribonuclease activity in Anacystis nidulans, an obligate photoautotroph. Udvardy,J., Sivok,B., Borbely,G., Farkas,G.L. (1976). J. Bacteriol. 126:630-633. [TOP OF PAGE]

  542. Physiology and ecology of bacteriophages of the marine bacterium Beneckea natriegens: salinity. Zachary,A. (1976). Appl. Environ. Microbiol. 31:415-422. The effects of variation in ionic levels on the stability and replication of two bacteriophages (nt-1 and nt-6) host specific for the marine bacterium Beneckea natriegens were examined. Monovalent cations influenced the adsorption of the nt-1 but not the nt-6 phage; however, one-step growth studies showed that NaCl was required for replication of both phage. The NaCl optimum for nt-1 production was 0.25 M NaCl, the same as the growth optimum for B. natriegens. However, the optimum for nt-6 production was 0.16 M NaCl. These NaCl optima for host and phage are at estuarine rather than oceanic levels. The nt-1 phage was better suited to replicate at NaCl levels typical of higher salinity areas (18-35%) and the nt-6 phage was better suited to replicate at lower salinities (5-18%). The nt phage were more resistant to low NaCl levels than their host bacterium and appeared limited to marine waters by the lower survival salinity of B. natriegens coupled with phage inactivation processes occurring in natural estuarine waters. [TOP OF PAGE]

  543. Studies in intracellular development and dynamics of biosynthesis of lytic enzymes of cyanophage LPP-1A in Plectonema boryanum cells. Zatula,D.G., Pilipenko,V.G., Mendzhul,M.I., Nesterova,N.V., Lysenko,T.G. (1976). Proc. Acad. Sci. ,URSR 2:178-181. [TOP OF PAGE]

  544. Isolation, identification, and partial characterization of cyanophage LPP-2N. Booth,S. (1975). University of Nebraska. [TOP OF PAGE]

  545. Field and ecological studies on blue-green algal viruses. Cannon,R. (1975). Proc.Symp.Water Qual.Manage.Through Biolog.Control. 112-117. Dep.Environ.Eng.Sci.Univ.Florida. [TOP OF PAGE]

  546. Co-evolution of a virus-alga system. Cowlishaw,J., Mrsa,M. (1975). Appl. Microbiol. 29:234-239. Plectonema boryanum, a filamentous blue-green alga, was cloned and then allowed to reach a steady state in a quasi-continuous culture in the presence of the algal virus, LPP-1. The culture was maintained for a 3.5-month period during which time at least four distinct culture lysings were evident. After the fourth lysis the culture reached a steady-state level which was identical in its algal concentration to the preinfection level. Upon testing the characteristics of the evolved alga and virus variants, the following was determined: cell variants resistant to both the original virus and the derived virus had evolved, and there was no evidence of lysogeny present among these cells. The evolved virus strains still grew on the parental algal strain, though with altered plaque morphology. Furthermore, they were antigenically similar to the parental virus, and showed no signficant difference in adsorption rate or growth characteristics on parental cells. However, a low-grade chronic viral infection persisted in the culture. Rapid re-establishment of a dense, stable culture is apparently the normal laboratory response of a procaryotic cell-virus system. [TOP OF PAGE]

  547. An electron microscopic study of the intracellular development of cyanophage A-4(L). Gromov,B.V., Khudyakov,I.Ya., Mamkaeva,K.A. (1975). Bull. Leningrad Univ. 15:74-76. [TOP OF PAGE]

  548. A comparative study of the cyanophages of Anabaena variabilis. Kozyakov,S.Y., Efremova,L.P. (1975). Bull. Leningrad Univ. 21:104-106. [TOP OF PAGE]

  549. Effect of certain physioco-chemical factors on the infectivity of cyanophages. Mendzhul,M.I., Bobrovnik,S.P., Lysenko,T.G., Schved,A.D. (1975). Mikrobiol. Zh. 37:73-79. [TOP OF PAGE]

  550. [Effect of several plant growth regulators on various prokaryotes and their viruses]. Menzel,G., Stenz,E., Toure,I.M., Gebler,B., Schuster,G. (1975). Z Allg Mikrobiol 15:259-268. 26 plant growth regulators including herbicides were investigated in their effect on the multiplication of Escherichia coli, Bacillus subtilis, and the blue-green alga Plectonema boryanum as well as the RNA phages M 12 and Qbeta and the DNA phages lambda, phi 105, and LPP-1 employing the agar diffusion method. Nearly all of the compounds inhibited and/or stimulated one or some of the prokaryotes tested. The most frequent and strongest effects occurred in Pl. boryanum, the least effects in E. coli. The multiplication of phages was also influenced by plant growth regulators leading to increase, decrease or non-appearance of plaques. The investigations with the temperate phages lambda and phi 105 suggested part of the compounds to be able to interfere with the process of lysogenization. The results are discussed comparatively involving correspondent findings referred to in literature. [TOP OF PAGE]

  551. Study of the structural proteins of LPP-1A cyanophage. Nesterova,N.V., Pilipenko,V.G., Mendzhul,M.I., Votselko,S.K. (1975). Mikrobiol. Zh. 37:606-609. [TOP OF PAGE]

  552. Electron microscopic study of the infection of Anacystis nidulans by the cyanophage AS-1. Pearson,N.J., Small,E.A., Allen,M.M. (1975). Virology 65:469-479. [TOP OF PAGE]

  553. Certain properties of lytic enzymes of LPP-1A cyanophage. Pilipenko,V.G., Nesterova,N.V., Mendzhul,M.I., Bobrovnik,S.P. (1975). Mikrobiol. Zh. 37:460-467. [TOP OF PAGE]

  554. Heat induction of the blue-green alga Plectonema boryanium lysogenic for the cyanophage SPIctsI. Rimon,A., Oppenheim,A.B. (1975). Virology 64:454-463. [TOP OF PAGE]

  555. Photoreactivation of UV-irradiated blue-green algae and algal virus LPP-1. Singh,P. (1975). Arch. Mikrobiol. 103:297-302. [TOP OF PAGE]

  556. Sensitization of algal virus to UV by the incorporation of 5-bromouracil and mutations of host alga Plectonema boryanum. Singh,P.K. (1975). Zeitsch. Allg. Mikrobiol. 15:547-552. [TOP OF PAGE]

  557. Photoreactivation of UV-irradiated blue-green algae and algal virus LPP-1. Singh,P.K. (1975). Arch. Microbiol. 103:297-302. [TOP OF PAGE]

  558. Lysogeny of blue-green alga Plectonuma boryanum by long tailed virus. Singh,P.K. (1975). Mol. Gen. Genet. 137:181-183. [TOP OF PAGE]

  559. Ecology of blue-green algal viruses. Cannon,R.E., Shange,M.S., DeMichele,E. (1974). J. Environ. Eng. Div. , ASCE 100:1205-1211. [TOP OF PAGE]

  560. The isolation of rhapidosomes from the blue-green alga, Spirulina. Chang,H.Y.Y., Allen,M.M. (1974). J. Gen. Microbiol. 18:121-??? [TOP OF PAGE]

  561. Viruses lysing blue-green algae. Goryushin,V.A., Chaplinskaya,S.M., Shainskaya,O.A., Lakosnik,V.N. (1974). pp. 45-53. In AnonymousViruses and Viral Diseases of Plants. Naukova Dumka, Kiev. [TOP OF PAGE]

  562. Viruses of blue-green algae. Goryushin,V.A., Chaplinskaya,S.M. (1974). pp. 9-17. In In Federov,V.D. and Telitchenko,M.M. (eds.), Topical Problems of the Biology of Bluegrene Algae. Nauka, Moscow. [TOP OF PAGE]

  563. Electron microscopic study of cyanophage A-1(L) development in the cells of blue-green alga Anabaena variabilis. Gromov,B., Kozyakov,S.Y., Mamkaeva,K.A., Gaevskaya,E.I. (1974). Bull. Acad. Sci. USSR,Biol. 2:286-288. [TOP OF PAGE]

  564. Preliminary characterization of a temperate phage system isolated from marine mud. Hidaka,T., Shirahama,T. (1974). Mem. Fac. Fish. ,Kagoshima Univ. 23:137-148. [TOP OF PAGE]

  565. A study of the survival of cyanophage AM-1 irradiated with UV and x-rays in cells of radiosensitive mutants of the blue-green alga Anacystis nidulans. Karbysheva,E.A., Goryushin,V.A., Mikhailyuk,D.P., Shestakov,S.V. (1974). Biol. Nauki. 17:118-121. [TOP OF PAGE]

  566. Marine transducing bacteriophage attacking a luminous bacterium. Keynan,A., Nealson,K., Sideropoulos,H., Hastings,J.W. (1974). J. Virol. 14:333-340. [TOP OF PAGE]

  567. A study of the development of cyanophage A-1(L) in a culture of the blue-green alga Anabaena variabilis. Kozyakov,S.Y. (1974). Bull. Leningrad Univ. 15:102-108. [TOP OF PAGE]

  568. Photosensitization of cyanophage N-1. McLaughlin,T., Lazaroff,N. (1974). J. Gen. Virol. 25:171-174. [TOP OF PAGE]

  569. Some biological properties of cyanophage LPP-1 strain. Mendzhul,M.I., Zhygir,V.V., Bobrovnik,S.P., Lysenko,T.G. (1974). Mikrobiol. Zh. 36:185-189. [TOP OF PAGE]

  570. Identification of virus LPP-1 isolates from artificial water bodies of the Dnieper. Mendzhul,M.I., Zhygir,V.V., Bobrovnik,S.P., Lysenko,T.G. (1974). Mikrobiol. Zh. 36:47-53. [TOP OF PAGE]

  571. Study of cyanophage LPP-1 adsorption onto cells of cyanophyceae (Plectonema boryanum). Mendzhul,M.I., Bobrovnik,S.A., Lysenko,T.G. (1974). Vop. Virus 1:31-36. [TOP OF PAGE]

  572. [Halotolerant forms of Bdellovibrio in the silt and water of Lake Balkhash and the Aral sea]. Mishustin,E.N., Nikitina,E.S., Berezina,F.S. (1974). IZVESTIIA AKADEMII NAUK SSSR. SERIIA BIOLOGICHESKAIA 127-128. [TOP OF PAGE]

  573. Infection of HeLa cells with nucleic acids of LPP group algophages. Moskovets,S.M., Mendzhul,M.I., Nesterova,N.V., Dyachenko,N.S., Vantsak,N.P., Lysenko,T.G. (1974). Mikrobiol. Zh. 36:43-46. [TOP OF PAGE]

  574. The characterization of a bacillus capsule of blue-green bacteriocidal activity. Reim,R.L., Shane,M.S., Cannon,R.E. (1974). Can. J. Microbiol. 20:981-986. [TOP OF PAGE]

  575. Isolation and genetic mapping of temperature-sensative mutants of cyanophage LPP2-SPI. Rimon,A., Oppenheim,A.B. (1974). Virology 62:454-569. [TOP OF PAGE]

  576. Inactivation of blue-green alga virus, AS-1, by isolated host lipopolysaccharide. Schnayer,N., Jenifer,F.G. (1974). Proc. Am. Phytopath. Soc. 1:144 [TOP OF PAGE]

  577. Isolation and characterization of a new virus infecting the blue-green alga Plectonema boryanum. Singh,P.K. (1974). Virology 58:586-588. [TOP OF PAGE]

  578. Isolation, enumeration, and host range of marine Bdellovibrios. Taylor,V.I., Baumann,P., Reichelt,J.L., Allen,R.D. (1974). Archives of Microbiology 98:101-114. [TOP OF PAGE]

  579. Cyanophages. Venkataraman,G.S., Kaushik,B.D. (1974). New Botanist 1:96-102. [TOP OF PAGE]

  580. Effect of caffeine and acriflavine on survival of UV-irradiated cyanophage AM-1 in the cells of radiosensitive mutants of Anacystis nidulans. Vorontsova,G.V., Karbysheva,E.A., Goryushin,V.A., Shestakov,S.V. (1974). Biol. Nauki. 11:107-110. [TOP OF PAGE]

  581. Isolation of bacteriophages of the marine bacterium Beneckea natriegens from coastal salt marshes. Zachary,A. (1974). Appl. Microbiol. 27:980-982. [TOP OF PAGE]

  582. Isolation and characterization of a virus infecting a blue-green alga of genus Synechococcus. Adolph,K.W., Haselkorn,R. (1973). Virology 54:230-236. [TOP OF PAGE]

  583. Blue-green algal virus N-1: Physical properties and disassembly into structural parts. Adolph,K.W., Haselkorn,R. (1973). Virology 427-440. The structure of N-1, a virus infecting the filamentous, nitrogen-fixing blue-green alga Nostoc muscorem, has been further characterized. The edge-to-edge distance of the N-1 head is 614 ± 18 Å; the length of the tail is 1000 ± 62 Å. Flexible beaded fibers are attached to the N-1 neck. Optical diffreaction of extended and contracted sheaths suggests that a rearrangement of protein subunits occurs upon contraction. The molecular weight of the viral DNA calculated from the sedimentation coefficient is 44 ± 3 X 106. Based upon the contour length of N-1 DNA molecules, the molecular weight is 41.8 ± 3.6 X 106. ¶ A survey has been made of the effects of a number of protein denaturing agents (urea and guanidine hydrochloride, anionic and cationic detergents, extremes of pH, and ultraviolet irradiation) upon the native viral morphology. For each agent tested, the first observable effect was to trigger a shortening (probably contraction) of the tail sheath. The most resistant viral substructure was the contracted sheath. From these investigations a hierarchy of increasing resistance to chemical degradation could be arranged: capside, tail core, tail sheath. [TOP OF PAGE]

  584. The effet of stress and non-stress conditions upon the interaction of Plectonema boryanum and the LPP-phycoviruses. Cannon,R.E. (1973). University of Delaware. [TOP OF PAGE]

  585. Genetics of blue-green algae and their viruses: isolation, characterization and mutagenesis of cyanophages. Chaubey,I.J. (1973). Banaras Hindu University, India. [TOP OF PAGE]

  586. Genetics of blue-green algae and their viruses. Choudhury,I.D. (1973). Banaras Hindu University, India. [TOP OF PAGE]

  587. The use of enrichment techniques to study marine bacterial viruses. Curtis,P., Nealson,K. (1973). Biol. Bull. 145:431-??? [TOP OF PAGE]

  588. Isolation of a new cyanophage, TAuHN-1. Kaushik,B.D., Venkataraman,G.S. (1973). Current Science 42:395-396. [TOP OF PAGE]

  589. The temperate cyanophage A-4 (L) of the blue-green alga Anabaena variabilis. Khudyakov,I.Y., Gromov,B.V. (1973). Mikrobiologija 904-907. [TOP OF PAGE]

  590. Morphogenesis of the virus of blue-green algae studied by electron microscopy. Kirillova,F.M., Chaplinskaya,S.M. (1973). Mikrobiologija 42:510-512. [TOP OF PAGE]

  591. Detection of A-1 virus of blue-green alga Anabaena varibilitis in the Kremenchug artificial reservoir. Mendzhul,M.I., Lysenko,T.G., Bobrovnik,S.A., Spivak,M.Y. (1973). Microbiol. Zh. 35:747-751. [TOP OF PAGE]

  592. Nucleotide composition of DNA in blue-green alga Plectonema boryanum and virus LPP-1. Nesterova,N.V., Sagun,T.S., Pilipenko,V.G., Aleksandrushkina,N.I. (1973). Mikrobiol. Zh. 35:126-129. [TOP OF PAGE]

  593. Cyanophages—viruses attacking blue-green algae. Padan,E., Shilo,M. (1973). Bacteriol. Rev. 37:343-370. [TOP OF PAGE]

  594. Phycoviruses. Safferman,R.S. (1973). pp. 214-237. In In Carr,N.G. and Whitton,B.A. (eds.), The Biology of Blue-Green Algae. University of California Press, Berkeley. [TOP OF PAGE]

  595. Special methods—virus detection in cyanophyceae. Safferman,R.S. (1973). pp. 145-158. In In Stein,J.R. (ed.), Handbook of Phycological Methods-Culture Methods and Growth Measurements. Cambridge University Press, London. [TOP OF PAGE]

  596. Ecophysiological aspects of blooming and the problem of pure water. Topatschewsky,A.V., Sirenko,L.A. (1973). Verh. Internat. Verein. Limnol. 18:1338-1347. [TOP OF PAGE]

  597. Cyanophage AC-1: a phage infecting unicellular and colonial blue-green algae. Venkataraman,G.S., Kaushik,B.D., Subramanian,G., Shanmugasundaram,S., Govindarajan,A. (1973). Current Science 42:104-105. [TOP OF PAGE]

  598. Comparison of the structures of blue-green algal viurses LPP-IM and LPP-2 and bacteriophage T7. Adolph,K.W., Haselkorn,R. (1972). Virology 47:701-710. [TOP OF PAGE]

  599. Photosynthesis and the development of the blue-green algal virus N-1. Adolph,K.W., Haselkorn,R. (1972). Virology 47:370-374. [TOP OF PAGE]

  600. Isolation and characterization of viruses infecting blue-green algae. Adolph,K.W. (1972). University of Chicago. [TOP OF PAGE]

  601. The effect of anibiotic stress on protein synthesis in the establishment of lysogeny of Plectonema boryanum. Cannon,R.E., Shane,M.S. (1972). Virology 49:130-133. [TOP OF PAGE]

  602. AS-1 virus adsorption to cells and spheroplasts of Synechococcus cedrorum. Desjardins,P.R., Barkley,M.B. (1972). Ann. Proc. Electron Microscope Soc. Am. 30:332-333. [TOP OF PAGE]

  603. Genetics of blue-green algae and their viruses. Dhar,B. (1972). Banaras Hindu University, India. [TOP OF PAGE]

  604. Gas vacuoles and other virus-like structures in blue-green algae. Fjerdingstad,E. (1972). Schweiz. Zeitsch. Hydrologie 34:135-154. [TOP OF PAGE]

  605. Isolation and host range studies of marine bacteriophages. Gill,M.L., Nealson,K. (1972). Biol. Bull. 143:463-464. [TOP OF PAGE]

  606. Aphanizomenon flow-aquae: infection by cyanophages. Granhall,U. (1972). Physiol. Plantarum 26:332-337. [TOP OF PAGE]

  607. On the stability of marine bacteriophages. Hidaka,T. (1972). Bull. Jap. Soc. Fish. 38:517-523. [TOP OF PAGE]

  608. Cyanophage A-1 (L) of hte blue-green alga Anabaena variabilis. Koz'yakov,S.Y. (1972). Microbiology 41:486-489. [TOP OF PAGE]

  609. A-1(L)—cyanophage of the blue-green alga Anabaena variabilis. Kozyakov,S.Y., Gromov,B.V., Khudyakov,I.Y. (1972). Mikrobiologija (Microbiologiia) 41:555-559. [TOP OF PAGE]

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