Bacteriophage Ecology Group - Reference Abstracts (1995)

	Bacteriophage Ecology Group Reference Abstracts (1995)
	Dedicated to the ecology and evolutionary biology of the parasites of unicellular organisms (UOPs)
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© Phage et al.	last updated on Wednesday, December 26, 2001

Viruses of Fungi and Lower Eukaryotes. Anonymous (1995). [TOP OF PAGE]
Relationships of tailed phages: a survey of protein sequence identity. Ackermann, H.-W., Elzanowski, A., Fobo, G., Stewart, G. (1995). Archives of Virology 140:1871-1884. [TOP OF PAGE]
A Bacillus phage that is a living fossil. Ackermann, H.-W., Yoshino, S., Ogata, S. (1995). Canadian Journal of Microbiology 41:294-297. Bacillus cereus phage Bace-11 has an isometric head and a contractile tail of about 500 nm in length, and is one of the two largest bacterial viruses known. Its tail, characterized by three long, whiplike fibers, is identical to giant phage tails produced by a Clostridium strain. These particles may represent phages of ancient origin that arose before the divergence of clostridia and bacilli. [TOP OF PAGE]
Microbiological quality of raw cow's milk at collection centers in Trinidad. Adesiyun, A.A., Webb, L., Rahaman, S. (1995). Journal of Food Protection 58:139-146. The microbial quality, pH and presence of selected pathogens in milk at eight collection centers in Trinidad were determined. The enterotoxigenicity and susceptibility of Staphylococcus aureus strains to antimicrobial agents and bacteriophages were investigated while the antibiograms and ability of Escherichia coli isolates to agglutinate O157 antiserum were also assessed. Of the 287 milk samples tested, the mean pH was 6.80 +- 0.10 and 207 (72.1%) were California mastitis test (CMT) positive. All (100.0%) milk samples contained S. aureus, and 217 (75.6%) were positive for E. coli. The ranges of mean counts per ml for total aerobic bacteria, S. aureus and E. coli were 3.3 yen 10-6 to 9.8 yen 10-7, 1.4 yen 10-4 to 1.2 yen 10-5 and 4.2 yen 10-4 to 1.6 yen 10-6, respectively. Ninety-three (40.4%) of 230 strains of S. aureus tested were enterotoxigenic producing staphylococcal enterotoxins A, B, C, D or a combination with SEC being predominantly elaborated. Of the 245 strains of S. aureus phage-typed, 123 (50.2%) were susceptible to international phage set (IPS) of bacteriophages. Overall, 49 (49.0%) of 100 strains of S. aureus tested were resistant to 1 or more of the 8 antimicrobial agents with resistance high to penicillin (48.0%), ampicillin (45.0%) and methicillin (21.0%). Among 100 strains of E. coli tested, 98 (98.0%) exhibited resistance to antimicrobial agents with high prevalence of resistance detected for cephalothin (79.0%), ampicillin (73.0%) and streptomycin (47.0%). Thirteen (6.9%) of 188 strains of E. coli agglutinated with O157 antiserum. It was concluded that the presence of some pathogens in milk in fairly high counts coupled with toxigenicity of some strains pose a health hazard to consumers. [TOP OF PAGE]
Characteristics of Staphylococcus aureus strains isolated from bovine mastitic milk: Bacteriophage and antimicrobial agent susceptibility, and enterotoxigenicity. Adesiyun, A.A. (1995). Journal of Veterinary Medicine Series B 42:129-139. Staphylococcus aureus strains isolated from bovine mastitic milk in Trinidad were examined for their susceptibility to bacteriophages and antimicrobial agents and their ability to produce enterotoxins. Phage 42D was used to screen for bovine strains of S. aureus in milk. Of 250 strains tested, 224 (89.6%) were sensitive to phages in the international phage set (IPS), 85 (34.0%) were resistant to antimicrobial agents and 134 (53.6%) were enterotoxigenic. Strains lysed by phages in various groups (mixed) were prevalent, 145 (58.0%), followed by strains sensitive to groups III (17.0%) and 1 (8.8%) phages. A total of 72 (28.8%) strains were used by phage 42D either alone or with others. Resistance to penicillin was most common with 59 (23.6%) strains while 44 (17.6%) and 43 (17.2%) strains were resistant to ampicillin and triple sulphur respectively. Only 3 (1.2%) strains were resistant to methicillin. Prevalence of resistance to penicillin (12.5%) amongst phage 42D-sensitive strains was significantly (P ltoreq 0.01; X-2) lower than for strains not lysed by phage 42D (28.1%) but strains susceptible to phage 42D were significantly (P ltoreq 0. 05; X-2)more resistant (4.2%) to methicillin than those not lysed by the phage (0.0%). Amongst 134 enterotoxigenic strains, 32 (23.9%), 77 (57.5%), 67 (50.0%) and 21 (15.7%) produced staphylococcal enterotoxins A(SEA), B(SEB), C(SEC) and D(SED) respectively either alone or mixed. SEB and SEC were significantly (P ltoreq 0.01; X-2) more produced than either SEA or SED. Strains lysed by groups IV, i.e. 42D (62.5%), and III (56.7%) were more enterotoxigenic than those sensitive to phages in groups II (45.5%) and non-typeable (46.2%) but the differences were not statistically significant (P ltoreq 0.05; X-2). Strains lysed by group II phages (72.7%) were significantly (P lt EQ 0.05; X-2) more resistant to antimicrobial agents than those lysed by phage 42D (18.8%). It was concluded that bovine mastitis strains of S. aureus in Trinidad were highly susceptible to bacteriophages and antimicrobial agents and enterotoxigenic and less than one-third may be considered to be bovine strains. [TOP OF PAGE]
Kinetics of pathogen destruction during storage of dewatered biosolids. Ahmed, A.U., Sorensen, D.L. (1995). Water Environment Research 67:143-150. The kinetics of pathogen destruction were determined during storage of digested and dewatered wastewater treatment biosolids to obtain relationships between temperature and duration of biosolids storage. Biosolids, seeded with Salmonella typhimurium, Yersinia enterocolitica. Campylobacter jejuni, bacteriophage f2, poliovirus, and Ascaris suum eggs were incubated at 5degree, 22degree, 38degree, and 49.5degree C, under both aerobic and anaerobic conditions for up to 62 days. Destruction of pathogens in stored biosolids occurred at all temperatures examined; however, rates increased with increasing temperature. There was no significant difference between the destruction of pathogens under aerobic or anaerobic conditions at all temperatures studied. At 50degree C, the decay rate of S. typhimurium, Y. enterocolitica, bacteriophage f2, poliovirus, and A. suum eggs was estimated to be 1.13, 1.10, 1.54, 0.81, and 0.21 log10 reductions per day, respectively. [TOP OF PAGE]
Bacillus cereus phage typing as an epidemiological tool in outbreaks of food poisoning. Ahmed, R., Sankar-Mistry, P., Jackson, S., Ackermann, H.-W., Kasatiya, S.S. (1995). Journal of Clinical Microbiology 33:636-640. Bacillus cereus is responsible for an increasing number of food poisoning cases. By using 12 bacteriophages isolated from sewage, a typing scheme for B. cereus isolates from outbreaks or sporadic cases of food poisoning was developed. The phages belonged to three morphotypes. Ten phages with contractile tails and icosahedral heads were members of the Myoviridae family, and two phages with noncontractile tails belonged to the Siphoviridae family. Phage II represented a new species. It had an isometric head and a very long contractile tail with long wavy tail fibers and was one of the largest viruses known. The vast majority of 166 B. cereus strains (161, or 97%) isolated from food poisoning cases were typeable. Of 146 strains isolated from 18 outbreaks, 142 (97%) could be divided into 17 phage types. A good correlation, on the order of 80 to 100%, between phage types of strains isolated from suspected foods and those of strains isolated from stools of symptomatic patients was observed. Most Bacillus thuringiensis strains were also typeable, providing further evidence of the close relatedness of B. cereus and B. thuringiensis. This phage typing scheme can be a valuable epidemiological tool in tracing the origins of food poisoning caused by B. cereus. [TOP OF PAGE]
Recovery of somatic coliphages in shellfish. Albert, M., Vannesson, C., Schwartzbrod, L. (1995). Water Science and Technology 31:453-456. [TOP OF PAGE]
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]
Suicide bombing, Bacillus style. Anonymous (1995). Discover Magazine December(December), 28-28. [TOP OF PAGE]
Distribution comparison between coliphages and phages of anaerobic bacteria (Bacteroides fragilis) in water sources, and their reliability as fecal pollution indicators. Armon, R., Kott, Y. (1995). Water Science & Technology 31:215-222. [TOP OF PAGE]
Electron microscopic investigation of lactic phages isolated in Turkey. Aydar, L.Y., Tunail, N. (1995). Milchwissenschaft 50:312-316. The host specifities and morphological characteristics of 24 virulent phages isolated from raw milk and wheysamples from different parts of Turkey and which affected 8 strains of Lactococcus lactis subsp. lactis, 3 of L. lactis subsp. diacetylactis, and 1 temperate phage were investigated. The temperate phage reported here is one induced from L. lactis subsp. lactis strain P131 by mitomycin C. Head structure, head dimensions, tail lengths, and tail widths of lactic phages were determined by electron microscopic analysis. The major phage groups were basically differentiated by their head structure as either prolate or isometric. Additional subgroupings were established using head dimensions or the possession of tail fibers as classification criteria. As a consequence 5 morphological groups were characterized. No relationship was found between the morphological groups and their host specifities. [TOP OF PAGE]
Effects of basal resources, predation, and alternative prey in microcosm food chains. Balciunas, D., Lawler, S.P. (1995). Ecology 76:1327-1336. Ecological theorists propose that the species composition of trophic levels can influence the relative strengths of top-down (predation) or bottom-up (nutrient) effects in food chains. We tested this by constructing two- and three-level food chains of bacteria and protists. Bacteria made up the first trophic level. The second level contained Chilomonas paramecium alone, Colpidium cf. striatum alone, or both together. Predatory Euplotes patella occupied the third trophic level. These assemblages were cultured in microcosms containing either low- or high-nutrient medium. Manipulating nutrients and predation produced comparable changes in the abundance of bacteria. In the second trophic level, Chilomonas was usually driven extinct by predation, but Colpidium was affected more by nutrients than predation because it had a partial size refuge from predation. Both species survived more poorly with predatory Euplotes if the other was present, because the predator was more abundant and persistent when both prey were available. The predator was less persistent in high-nutrient microcosms, because additional nutrients boosted the proportion of Colpidium populations within the size refuge. This type of mechanism could limit trophic cascades in food chains where resources affect prey vulnerability. [TOP OF PAGE]
Virus and bacteria transport in a sandy aquifer, Cape Cod, MA. Bales, R.C., Li, S., Maguire, K.M., Yahya, M.T., Gerba, C.P., Harvey, R.W. (1995). Ground Water 33:653-661. [TOP OF PAGE]
Speculations on the influence of infecting phenotype on virulence and antibiotic susceptibility of Legionella pneumophila. Barker, J., Brown, M.R. (1995). J. Antimicrob. Chemother. 36:7-21. It is not clear how Legionella pneumophila, which is a ubiquitous aquatic organism not possessing a mammalian reservoir, evolved the ability to cause human disease. The unusual ecology of the organism may play an important role in the transmission and virulence of legionella infections. L. pneumophila can infect and kill specific species of free-living amoebae as well as multiplying as an intracellular parasite in human phagocytic cells. In nature L. pneumophila can survive and possibly replicate in free suspension, and grow in biofilms and in protozoa thus leading to diverse phenotypes, potentially with diverse virulence and susceptibility properties. Indeed, recent evidence shows that intra-amoeba growth induces a phenotype that is dramatically different physiologically to that obtained in vitro, with altered virulence and susceptibility properties. Growth in macrophages also has profound effect on the physiological properties of L. pneumophila. Many different stress proteins are expressed by the organism as a result of intra-macrophage growth. A heat shock protein is abundantly synthesised and may be presented on the surface of infected macrophages, which allows them to be targeted by T-lymphocytes for destruction. The difficulties in successfully treating Legionnaires' disease are probably influenced by the intracellular location of L. pneumophila. Retrospective clinical studies show that it is only drugs such as erythromycin, ciprofloxacin and rifampicin, which are capable of accumulating in phagocytic cells, that are efficacious in the treatment of legionnaires' disease. Despite the use of such drugs treatment failures occur, but these do not appear to be associated with the emergence of resistant strains. Studies have shown that although erythromycin and rifampicin can inhibit the multiplication of L. pneumophila in macrophages the organism is not killed and can resume multiplying when the drugs are removed. Thus a competent cell mediated immune response is important in recovery from legionella infections. There is an urgent need for greater understanding of how the changes induced by intracellular growth affect sensitivity to antibiotics and of how the changes induced by intracellular growth affect sensitivity to antibiotics and host defences. Immunocompromised patients, who have the highest mortality rates, are likely to gain the most from progress in the treatment of L. pneumophila infections. [TOP OF PAGE]
Bor Gene of phage lambda, involved in serum resistance, encodes a widely conserved outer membrane lipoprotein. Barondess, J.J., Beckwith, J. (1995). J. Bacteriol. 177:1247-1253. bor is one of two recently identified genes of phage lambda which are expressed during lysogeny and whose products display homology to bacterial virulence proteins. bor is closely related to the iss locus of plasmid ColV,I-K94, which promotes bacterial resistance to serum complement killing in vitro and virulence in animals. bor has a similar in vitro effect. We show here that the bor gene product is a lipoprotein located in the Escherichia coli outer membrane. We also find that antigenically related proteins are expressed by lysogens of a number of other lambdoid coliphage, in cells carrying the cloned iss gene, and in several clinical isolates of E. coli. These results demonstrate that bor sequences are widespread and present a starting point for mechanistic analysis of bor-mediated serum resistance. [TOP OF PAGE]
Biological effectiveness of environmental radiation in surface measurements by phage T7. Berces, A., Gaspar, S., Fekete, A., Kuluncsics, Z. (1995). Journal of Photochemistry and Photobiology B Biology 31:87-90. Biologically effective ultraviolet doses have been measured on summer days, at different sites of Hungary during 1994. For parallel measurements, phage T7 biological dosimeter and Robertson-Berger meters have been used. Results of cumulated daily doses and daily profiles are demonstrated for both direct and global radiation. A suggestion for the optimal number of measuring sites in a UV level forecasting system is given. [TOP OF PAGE]
Biology of DNA restriction. Bickle, T.A., Krüger, D.H. (1995). Microbiol. Rev. 57:434-450. [TOP OF PAGE]
Ground Water Pollution. Bitton, G., Gerba, C.P. (1995). John Wiley and Sons, New York.[TOP OF PAGE]
High frequency of conjugation versus plasmid segregation of RP1 in epiphytic Pseudomonas syringae populations. Bjorklof, K., Suoniemi, A., Haahtela, K., Romantschuk, M. (1995). Microbiology (Reading) 141:2719-2727. The maintenance and transfer of the broad host-range plasmid RP1 in epiphytically growing populations of Pseudomonas syringae was monitored in the phyllosphere of bush bean (Phaseolus vulgaris). When foliage was inoculated with plasmid-containing bacteria, the plasmid was lost from the majority of the cells within 2 d but was stably maintained in 0.8% of the population. A high frequency of conjugation between added donors and recipients was observed under high humidity conditions. In 1 d, the number of transconjugants rose to 10^-1 of the donors and the proportional level of transconjugants continued to increase until 3 d after inoculation. Under these conditions the proportion of plasmid- containing bacteria stabilized at about 0.8% of the total population. The conjugation rate appeared to be in equilibrium with plasmid loss and the slower growth of the plasmid-carrying cells. A factor that influenced the high conjugation frequency observed was the available nutrients provided by the leaf and also, to a lesser extent, the leaf surface itself. Transfer of the plasmid from added donors to indigenous bacteria was also studied, using a donor-specific bacteriophage for counterselection of the donor. Transfer was observed to 10 different species of Gram-negative epiphytically growing bacteria. The bean leaf surface appears to function as a hotspot at least for intraspecific transfer of plasmids in high humidity. The frequency of transfer was higher than in soil or in rhizosphere habitats. This is likely to be the result of an environment that is nutritionally rich in combination with a limited colonizable surface area which permits close contact between the bacterial cells. [TOP OF PAGE]
Differential accumulation and depuration of human enteric viruses by mussels. Bosch, A., Pintó, R.M., Abad, F.X. (1995). Water Science & Technology 31:447-451. [TOP OF PAGE]
Viruses—the new players in the game: their ecological role and could they mediate genetic exchange by transduction? Bratbak, G., Heldal, M. (1995). pp. 249-264. In AnonymousMolecular Ecology of Aquatic Microbes. Spring-Verlag KG, Berlin, Germany. [TOP OF PAGE]
Viral activity in relation to Emiliania huxleyi blooms—a mechanism of DMSP release. Bratbak, G., Levasseur, M., Michaud, S., Cantin, G., Fernandez, E., Heimdal, B.R., Heldal, M. (1995). Mar. Ecol. Prog. Ser. 128:133-142. [TOP OF PAGE]
Genetic conflicts and parasitism. Brookfield, J. (1995). Trends in Ecology & Evolution 10:138-139. [TOP OF PAGE]
Effects of grazing, sedimentation, and phytoplankton cell lysis on the structure of a coastal pelagic food web. Brussaard, C.P.D., Riegman, R., Noordeloos, A.A.M., Cadee, G.C., Witte, H., Kop, A.J., Nieuwland, G., van Duyl, F.C., Bak, R.P.M. (1995). Mar. Ecol. Prog. Ser. 123:259-271. [TOP OF PAGE]
Characterization of a temperate Streptococcus thermophilus bacteriophage and its genetic relationship with lytic phages. Brussow, H., Bruttin, A. (1995). Virology 212:632-640. The temperate Streptococcus thermophilus bacteriophage vf-SFi21 showed an 38-kb-long double-stranded DNA genome with cohesive ends. A single integration site was used in lysogens established in three different S. thermophilus strains. The attP and attB sites were localized on the restriction map of phage DNA and by hybridization on pulsed field separated bacterial DNA. All laboratory-established lysogens showed in addition to integrated prophage DNA unintegrated monomer phage DNA with unligated cos sites. The genetic relatedness of vf-SFi21 DNA with DNA from lytic phages was studied in dot blot and Southern blot hybridization by using individual restriction fragments of vf- SFi21 DNA as probes. Lytic group I phages hybridized with fragments of the central and the right part of the vf-SFi21 genome but failed to hybridize with a fragment joining both parts. Lytic group II phages showed hybridization with the right half of the vf-SFi21 genome. In lytic group IV phages, biologically a heterogeneous group, many different combinations of cross hybridization were detected in accordance with the hypothesis of the modular evolution of phage genomes. [TOP OF PAGE]
Parasitology year 2000. Bush, A.O., Caira, J.N., Minchella, D.H., Nadler, S.A., Seed, J.R. (1995). Journal of Parasitology 81:835-842. We predict that in order for parasitology to thrive by the year 2000 the various subdisciplines of evolution, ecology, biosystematics, and genetics must develop holistic approaches and use parasite models to answer basic biological questions. The students of tomorrow must work as part of a multidisciplinary team; and their questions and answers must be conceptually integrated into the broader biological framework of evolution and ecology. [TOP OF PAGE]
Comparative survival of hepatitis-A virus, poliovirus and indicator viruses in geographically diverse seawaters. Callahan, K.M., Taylor, D.J., Sobsey, M.D. (1995). Water Science & Technology 31:189-193. [TOP OF PAGE]
Large Pseudomonas phages isolated from barley rhizosphere. Campbell, J.I.A., Albrechtsen, M., Sorensen, J. (1995). FEMS Microbiol. Ecol. 18:63-74. Five bacteriophages infecting common fluorescent pseudomonads (Pseudomonas fluorescens and Pseudomonas putida) were isolated from barley rhizosphere soil. Morphological and molecular characteristics of the phages are described together with selected phage-host interactions. All phages belonged to the Myoviridae family with isometrical heads on contractile tails; 4 of them were unusually large and had complex protein and DNA profiles. The large phages had estimated genome sizes of 200 kb or more. Restriction enzyme analyses and DNA-DNA hybridizations showed that all isolates represented different phage species. None of the isolates were observed to establish lysogeny with the main host strain, P. putida MM1. The large phages multiplied slowly on their hosts, producing very small plaques; one-step growth experiments with one of the large phages (Psp 4) hence demonstrated a long latent period (2.5 h) and a very small burst size (10 particles). One of the large phages (Psp 3) was abundant in the rhizosphere (approx. 10-4 pfu g-1 soil) and had a particularly broad host range which extended to both fluorescent (Pseudomonas aeruginosa, P. fluorescens, P. putida and Pseudomonas chlororaphis) and non-fluorescent (Pseudomonas stutzeri) Pseudomonas spp. occurring in soil. The ecological importance of the large Pseudomonas phages must be further studied, but their slow multiplication rates suggested a possible mechanism of balanced phage-host co-existence in the rhizosphere. [TOP OF PAGE]
Detection of coliphages and enteroviruses in sewage and aerosol from an activated sludge wastewater treatment plant. Carducci, A., Arrighi, S., Ruschi, A. (1995). Letters in Applied Microbiology 21:207-209. Coliphages and enteroviruses were monitored over 12 months in sewage and air adjacent to an activated sludge plant. Both showed temporal variation but the mean count of phages in enterovirus-positive samples was not significantly different from that in enterovirus-negative samples. Hence coliphages are not necessarily a good indicator of enteroviruses in sewage and aerosols. [TOP OF PAGE]
Isolation and characterization of temperature and virulent bacteriophages of Lactobacillus plantarum. Caso, J.L., De Los Reyes Gavilan, C.G., Herrero, M., Montilla, A., Rodriguez, A., Suarez, J.E. (1995). Journal of Dairy Science 78:741-750. Several bacteriophages that are able to infect Lactobacillus plantarum have been isolated by induction of lysogenic strains with mitomycin C and by enrichment of samples from different origins. Two closely related phages (PHI-LP1-A and PHI- LP1-B), isolated from corn silage, and phage PHI-LP2, isolated from a homemade cheese whey, were characterized. Some features of L. plantarum phage fri were also studied that have not been previously published. Virions of the PHI-LP1 and PHI-LP2 groups displayed a typical B1 morphology (Siphoviridae); heads were isometric, and tails were long and noncontractile. The genetic material of the virions was a single molecule of double- stranded DNA without cohesive ends. The genome lengths were 80 kbp (PHI-LP1 group), 47 kbp (PHI-LP2), and 133 kbp (fri). Host range was limited to some strains of L. plantarum. Temperature of propagation affected the appearance and aspect of the plaques of lysis. Phage adsorption was quite efficient, reaching gt 90% in most cases and often gt 99%, and was not affected by the temperature. One-step growth experiments showed that, in some cases, temperature strongly influenced the phage development. The temperate nature of the phages could only be established for phage PHI-LP2, and no lysogens were obtained for members of the PHI-LP1 group. [TOP OF PAGE]
Links and interactions between mycoplasmas and viruses: Past confusions and present realities. Chastel, C. (1995). Archives of Virology 140:811-826. Links between mycoplasmas and viruses are ancient, multiple and complex, from past confusions during the first decades of the virus era to present realities illustrated by the possible implication of mycoplasms as co-factors in natural infections of AIDS. Mycoplasma viruses (phages) may also be responsible for modifying the pathogenic power of mycoplasmas, at least for plants and insects. In addition, several mycoplasmas are able to act as undesirable cell culture contaminants that induce erroneous results in both applied and general virology. These problems are examined within a historical context. [TOP OF PAGE]
A role for bacteriophages in the evolution and transfer of bacterial virulence determinants. Cheetham, B.F., Katz, M.E. (1995). Molecular Microbiology 18:201-208. A virulence-associated region in the genome of Dichelobacter nodosus has been shown to contain an integrase gene which is highly related to the integrases of Shigella flexneri phage Sf6 and coliphages P4 and PHI-R73, together with open reading frames (vapB, C and D) related to genes borne on plasmids in Neisseria gonorrhoeae, Escherichia coli, Actinobacillus actinomycetemcomitans and Treponema denticola. Similar to P4 and PHI-R73, the vap region is bracketed by putative Actinobacillus bacteriophage at sites and is adjacent to a tRNA gene, which suggests that the vap region has been derived by the integration of a bacteriophage, or a plasmid carrying a bacteriophage-related integrase gene. Many similarities in genes and genes clusters encoding virulence determinants have been found in distantly related bacteria. These genes are often located on plasmids in one organism but on the chromosome in others, implying that transmission of the genes has been followed by integration. Thus, the events which have generated the vap regions of D. nodosus may represent a common mechanism for transfer of virulence determinants. A number of genes involved in the virulence of bacterial pathogens are found on integrated bacteriophages, and we suggest that others will prove to be associated with tRNA genes and/or integrase genes derived from bacteriophages. The use of tRNA genes as integration sites for many bacteriophages and plasmids may favor intergeneric transmission, as tRNA genes are highly conserved. [TOP OF PAGE]
Nested PCR with three highly degenerate primers for amplification and identification of DNA from related organisms. Chen, F., Suttle, C.A. (1995). BioTechniques 18:609-611. This paper reports that three highly degenerate primers can be used in nested PCR, and that the second amplification can be done directly on DNA fragments excised from low melting temperature agarose. The approach provides rapid confirmation that the correct targets have been amplified. It is useful when only one internal probe sequence (or gene-specific primer) is available to confirm the identity of a PCR product, and a degenerate primer sequence must be derived from an amino acid sequence. This can occur, for example, when DNA must be amplified from a group of related organisms. [TOP OF PAGE]
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]
Studies on diagnostic bacteriophage of Vibrio fluvialis. [Chinese]. Chen, K., Lin, Y., Chen, G. (1995). Chung-Hua Yu Fang i Hsueh Tsa Chih [Chinese Journal of Preventive Medicine] 29:138-140. Species of Vibrio fluvialis are identified by their biochemical characteristics so far, with a lot of items to be determined, overelaborate procedure and expensiveness. Inaccordance with the fact that bacteriophage is a specific parasite inhabited in bacteria and has been used in identifying other bacteria with high specificity, some of Vibrio fluvialis bacteriophage isolated from natural environment were selected to make diagnostic preparation for Vibrio fluvialis identification. Diagnostic positivity of Vibrio fluvialis averaged 84.27%, and 87.84% for those of human source. Cross-lysis rates both for the same Vibrio genus and that of different families in the same genus were less then 3%, and no cross-lysis was found for the other enteric bacteria in different genera. There was no significant difference between diagnostic bacteriophage and biochemical tests for Vibrio of unknown species. This method was highly specific, sensitive, rapid, simple and inexpensive, and could be used in diagnosis of Vibrio fluvialis. [TOP OF PAGE]
Trypanosoma cruzi trans-sialidase: enhancement of virulence in a murine model of Chagas' disease. Chuenkova, M., Pereira, M.E. (1995). J. Exp. Med. 181:1693-1703. Trypanosoma cruzi, the etiological agent of Chagas' disease, expresses a trans-sialidase at highest levels in infective trypomastigotes, where it attaches to the plasma membrane by a glycophosphoinositol linkage. Bound enzyme sheds into the extracellular milieu in a soluble form. Experiments performed in vitro suggest that the trans-sialidase participates in several parameters of T. cruzi-host interactions, like cell adhesion and complement resistance. However, the role that membrane-bound and soluble trans-sialidase plays in the infection of mammals is not understood. To begin to study the role the enzyme may play in vivo, T. cruzi trypomastigotes were inoculated subcutaneously into mice that had been sensitized for various times with the purified protein. A single dose of either endogenous or recombinant trans-sialidase injected into the connective tissues of BALB/c mice greatly enhanced parasitemia and mortality. Maximum enhancement was achieved with 1-2-h priming. Injection of the enzyme after the parasites had been established in the inoculation site had little, if any, consequence in modifying virulence. The enhancement did not seem to be through a direct effect of the enzyme on trypomastigote-host cell interactions because it occurred when the sites of trans-sialidase sensitization and parasite inoculation were physically separate. Rather, virulence enhancement seemed to depend on inflammatory cells, since priming with trans-sialidase had no significant effect in severe combined immunodeficiency mice, which lack functional T and B lymphocytes. However, antibody response to T. cruzi in the trans-sialidase-primed BALB/c mice was the same as in the control animals. Virulence enhancement was specific for the trans-sialidase because it did not occur in mice primed with Newcastle virus sialidase, which has the same substrate specificity as the T. cruzi enzyme, or with the sialidase from the bacterium Vibrio cholerae, whose substrate specificity is broader than the trypanosome sialidase. Furthermore, no enhancement of virulence occurred after sensitization with another adhesion protein (penetrin) purified from T. cruzi trypomastigotes and engineered bacteria, nor with bacterial lipopolysaccharide. The virulence-promoting activity of soluble trans-sialidase in the mouse model may be physiologically relevant because it was achieved with tiny doses, approximately 1-2 microgram/kg, raising the possibility that neutralization of the enzyme with specific probes could impair the development of Chagas' disease. In fact, a monoclonal antibody specific for the tandem repeat in the trans-sialidase COOH terminus enhanced infection of BALB/c mice, in agreement with earlier experiments in vitro, whereas antibodies against an amino acid sequence in the Cys region had the opposite effect. [TOP OF PAGE]
Lysotypie des Acinetobacter. Coffi, H. (1995). Laval University, Quebec, Canada. [TOP OF PAGE]
Bacteriophages in mussels and in waters for the cultivation of molluscs [Batteriofagi nei mitili e in acque per la molluschicoltura]. Contato, E., Mirolo, G., Sartea, A., Tampieri, M.L., Tuffanelli, A., Chiccoli, M., Bucci, G. (1995). Igiene Moderna [IG. MOD. ] 103:361-371. For some time now, coliphages have been proposed as enterovirus detectors in water owing to their resistance to chlorination and environmental stress and to their morphologic and biochemical characteristics which are similar to those of the enteroviruses. In this study, we have compared data regarding the analysis of 157 samples of water for the production of molluscs and 157 samples of mussels (Mytilus galloprovincialis) cultivated in these waters. Both in the samples of water and in the mussels we looked for the presence of E. coli, Salmonella and E. coli bacteriophages. Furthermore, in 148 samples of mussels, we looked for the presence of fecal coliforms. The search for bacteriophages was carried out with the "plaque count in agar" method. None of the samples showed the presence of Salmonella. Comparison of the data shows that there is no correlation between bacterial organisms and phages. The average monthly trend values of E. coli and phages present in mussels and water show a substantial increment during autumn and winter. [TOP OF PAGE]
Viruses and the Environment. Cooper, J.I. (1995). Chapman and Hall, London.During the decade since the publication of the first edition of this important book there has been a rapid advancement in the techniques of genetic engineering and molecular biology. In this revised edition these advances are taken into account and the book includes such topics as gene therapy, immunosuppression and new viruses of human/veterinary significance. Much new information about virus transmission is also included and the most modern systems of virus taxonomy are used to emphasize the features shared between viruses in plants, animals, and bacteria. This is the only book of its type which covers the viruses in all forms of life. This book is of value to students and professsional from fields as diverse as molecular biology and microbiology to environmental and agricultural science. [phage ecologists may be particularly interested in chapter 6 titled, "Strategies of virus maintenance in communities" - STA]. [TOP OF PAGE]
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]
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]
Cell surface differences in lactococcal strains. Crow, V.L., Gopal, P.K., Wicken, A.J. (1995). International Dairy Journal 5:45-68. A number of cell surface properties were compared in 15 pairs of lactococcal strains in order to gain an understanding of cell surface diversity and the relationship between the acquisition of the phage-resistance phenotype and alteration of cell surface properties. Each pair comprised a parent strain and a derivative resistant to a phage (PHI-R) or a number of phages. Three cell surface hydrophobicity patterns were found: (1) three parent strains were more hydrophobic than their O-R derivatives; (2) five PHI-R derivatives were more hydrophobic than their parent strains; (3) there were no differences for seven strain pairs. Loosely associated cell surface material was removed without cell lysis, and concentration differences between 28 strains of 40-, 23- and 11-fold were found for the extracted protein, hexose and thamnose, respectively. These three surface components were extracted in higher concentrations from the PHI-R derivative for seven strain pairs and from the parent strain for three strain pairs, and no differences were observed for four strain pairs. Intracellular and extracellular lipoteichoic acid concentrations varied in four of six strain pairs studied. The extracted protein profiles determined on polyacrylamide gels and by Superose 12 chromatography and the compositions of the extracted polysaccharide were different between most of the strain pairs. In addition, the surface properties, particularly cell hydrophobicity, varied according to growth conditions for some strains. The cell-surface components showed considerable diversity within the 30 lactococcal strains studied, with multiple differences between many of the strain pairs. For example, differences in hydrophobicity, the extracellular lipoteichoic acid concentration, molecular weight profile of proteins and the amount of protein, hexose and rhamnose extracted as loosely associated cell surface material were observed between the strains of pair E8/398. No unifying theme was evident to describe the basis of changes to the cell surface in the phage-resistant derivative strains. [TOP OF PAGE]
The influence of phage-assisted Lysis of Lactococcus lactis subsp. lactis ML8 on cheddar cheese ripening. Crow, V.L., Martley, F.G., Coolbear, T., Roundhill, S.J. (1995). International Dairy Journal 5:451-472. Cheddar cheese was made with Lactococcus lactis subsp. lactis strain ML8 as starter and two levels of rennet and three levels of homologous phage. The use of the different phage levels in cheese milk resulted in various degrees of starter lysis early in the ripening process. The levels of activity of two starter cytoplasmic enzymes, lysylaminopeptidase and FBP-aldolase, in the cheese matrix were used as a direct measure of lysis and increased with the level of phage added. Elevated starter lysis was associated with an increased rate of formation of amino acids and ammonia but the removal rate of lactose in the cheese was decreased. The relative levels of hydrophobic and hydrophilic peptides in aqueous cheese extracts were also influenced by the extent of starter lysis. Bitter flavour was prominent in cheese with high rennet concentration, but not when there was also high starter lysis. The results suggest that a balance of lysed and intact cells is important for control of cheese ripening; enzymes released on cell lysis accelerate the rate-limiting peptidolytic steps and removal of some bitter peptides, while intact cells are required for lactose removal. The consequences of the relative levels of intact and lysed cells on substrate-enzyme interactions, enzyme stability and flavour profiles are discussed. [TOP OF PAGE]
Incidence of lysogeny in wild lactococcal strains. Cuesta, P., Suarez, J.E., Rodriguez, A. (1995). Journal of Dairy Science 78:998-1003. The incidence of lysogeny among 172 lactococcal strains, isolated from natural dairy fermentations and selected by their high capacity to coagulate milk and to produce lactic acid, was studied. Lysis of 92 strains (53% of the strains tested) was observed after using mitomycin C for induction of cultures. Fifty- one of these 92 strains released phages that were able to propagate on indicator strains. Twenty-eight (16%) of the 172 strains tested acted as host for at least one phage, although some supported the development of more than one phage isolate. Spontaneous induction was insignificant in gt 50% of strains inducible by mitomycin C, but titers after mitomycin C induction varied between 10-1 and 10-6 pfu/ml. No plaque formation was observed at 37 degree C. The bacteriophages belonged to the family Siphoviridae, as revealed by electron microscopy. Head and tail dimensions ranged widely. Some temperate phages that were unable to form plaques of lysis appeared to be defective viral particles. [TOP OF PAGE]
Characterisation of four Leuconostoc bacteriophages isolated from dairy fermentations. Davey, G.P., Ward, L.J.H., Brown, J.C.S. (1995). FEMS Microbiol. Let. 128:21-26. Four bacteriophages (phages) growing on the same Leuconostoc strain were characterized. Electron micrographs showed these phages to be similar in morphology to the commonly isolated lactococcal phages with head diameters ranging from 49-55 nm and tail lengths of 117-131 nm. A distinctive base plate and collar were also present. From restriction enzyme analysis of purified phage DNA, the genome sizes were 23-29 kb. All four phages showed one major structural protein (of approximately 24 kDa) on SDS polyacrylamide gels. Hybridization experiments confirmed that the phages belonged to the same homology group. There was no homology between DNA from these phages and DNA from a prolate or small isometric lactococcal phage. [TOP OF PAGE]
Developing new starters for fermented milk products. Davidson, B.E., Hillier, A.J. (1995). Australian Journal of Dairy Technology 50:6-9. The production of fermented milk products has evolved from a cottage industry to a large scale, factory-based manufacturing process within a century. One consequence of this rapid evolution of technology has been that the demand for suitable starter strains has become more stringent. A satisfactory dairy fermentation requires a stable, predictable rate of acid production. Phage infection must not be allowed to interfere with this. Ultimately the fermented product must develop a desirable, long-lasting flavour - preferably after spending the minimum time in storage. The development of successful starter strategies to meet these requirements has involved the application of established bacteriological techniques with particular care being devoted to strain characterisation. Detailed analyses of the molecular genetics of different lactic acid bacteria has been feasible for little more than a decade, but the tempo of discovery has increased dramatically throughout this period. For Lactococcus lactis, which is a commonly used starter for cheese manufacture, the situation now exists where there are excellent prospects for directed molecular approaches to strain improvement. Thus, with the aid of biotechnology it should be possible to identify and/or construct starter strains that have: good flavour-producing characteristics, satisfactory rates of acid production and improved phage resistance properties. [TOP OF PAGE]
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]
Relationships among Actinomyces naeslundii (A. viscosus) bacteriophages isolated from sewage and the oral cavity. Delisle, A.L., Donkersloot, J.A. (1995). Microbial Ecology in Health & Disease 8:121-127. Several lytic phages of Actinomyces naeslundii genospecies 2 (formerly A. viscosus) have been isolated from sewage and from dental plaque. To define the relationships between these phages and ultimately to assess their role in the ecology of the human oral cavity, 13 phages isolated from these two environments were purified and their biochemical properties compared. Five small, short-tailed phages, isolated from sewage over the course of several years (Av-1, Av-2, Av-3, 1281, and BF307) were morphologically indistinguishable from each other and from five phages recovered more recently from human dental plaque (CT1, CT2, CT3, CT6 and CT7). The small phages (all morphotype C1) contained double-stranded linear DNA, 18 kb in size. In contrast, three phages from dental plaque (CT4, CT5 and CT8) possessed longer tails and much larger head structures (morphotype B1). Two of the larger phages (CT4 and CT5) contained DNA genomes estimated to be 80 kb in size, whereas large phage CT8 contained DNA of approximately 50 kb. Restriction endonuclease analysis revealed extensive differences between the large and small phages but the latter group showed similar, and in several cases identical, fragment patterns. These results indicate the existence of at least three distinct types of lytic bacteriophage active against oral Actinomyces spp. The similarities between the sewage and small dental plaque isolates indicate a high degree of relatedness and suggest that the sewage phages probably originated from the oral cavity. [TOP OF PAGE]
Phylogeny of Aureococcus anophagefferens and a morphologically similar bloom-forming alga from Texas as determined by 18S rDNA sequence analsysis. DeYoe, H.R., Chan, A.M., Suttle, C.A. (1995). Journal of Phycology 31:413-418. [TOP OF PAGE]
Bacteriophage resistance in Lactococcus. Dinsmore, P.K., Klenhammer, T.R. (1995). Molecular Biotechnology 4:297-314. Lactic acid bacteria are industrial microorganisms used in many food fermentations. Lactococcus species are susceptible to bacteriophage infections that may result in slowed or failed fermentations. A substantial amount of research has focused on characterizing natural mechanisms by which bacterial cells defend themselves against phage. Numerous natural phage defense mechanisms have been identified and studied, and recent efforts have improved phage resistance by using molecular techniques. The study of how phages overcome these resistance mechanisms is also an important objective. New strategies to minimize the presence, virulence, and evolution of phage are being developed and are likely to be applied industrially. [TOP OF PAGE]
Neutralizing recombinant human antibodies to a conformational V2- and CD4-binding site-sensitive epitope of HIV-1 gp120 isolated by using an epitope-masking procedure. Ditzel, H.J., Binley, J.M., Moore, J.P., Sodroski, J., Sullivan, N., Sawyer, L.S., Hendry, R.M., Yang, W.P., Barbas, C.F., Burton, D.R. (1995). Journal of Immunology 154:893-906. As part of the goal of assembling a mixture of neutralizing human mAbs for possible prophylaxis and therapy of HIV-1 disease, we describe a strategy by which neutralizing human Abs to a weakly immunogenic epitope can be accessed. From a phage display library derived from an asymptomatic HIV-1 seropositive donor, a panel of recombinant Fabs against the CD4 binding site (CD4bs) of gp120 was retrieved by affinity selection using recombinant gp120 (strain LAI). Two Fabs corresponding to the dominant clones were used to mask the CD4bs epitope(s) before repeating the selection procedure. Four Fabs were then retrieved that had novel heavy chain sequences. Three recognized a novel epitope distinct from that recognized by conventional CD4bs Abs and were defined by the following criteria: 1) second V region (V2 region) dependence indicated by sensitivity to amino acid changes in the V2 loop and by competition with murine anti-V2 mAbs; 2) CD4bs dependence indicated by sensitivity to amino acid changes usually associated with CD4 binding and by inhibition of Fab binding to gp120 by soluble CD4; this dependence seemed to arise via conformational changes rather than by direct binding, as CD4bs Abs enhanced binding of two of the novel Fabs and, in a reversal of the competition format, the novel Fabs did not inhibit soluble CD4 binding to gp120; and 3) equivalent binding to glycosylated and deglycosylated gp120 and significant, although much reduced, binding to denatured gp120 in contrast with CD4bs Abs, which do not bind to deglycosylated or denatured gp120. One of the novel Fabs efficiently neutralized the MN and LAI strains of HIV-1. These results indicate the presence of a novel neutralizing conformational epitope on gp120 sensitive to the V2 loop and the CD4bs and further highlight the conformational flexibility of gp120. The strategy of masking highly immunogenic epitopes with Abs to rescue a broader range of specific Abs from combinatorial libraries should be widely applicable. [TOP OF PAGE]
Somatic and F-specific coliphages in New Zealand waste treatment lagoons. Donnison, A.M., Ross, C.M. (1995). Water Res. 29:1105-1110. Three coliphages (FRNA, FDNA and somatic) and three bacteria) indicators (faecal coliforms, Escherichia coli and enterococci) were measured in four waste-treatment lagoons over 10 months. Two of the lagoons treated domestic sewage; the third, meat processing waste and the fourth, meat processing waste with a minor sewage component. In the meat processing lagoons the ratios of FRNA:FDNA were numerically large, due to very low counts of FDNA, and somatic coliphages generally outnumbered FRNA. Many of the FDNA plaques from meat processing lagoons were very small and were not confirmed on the F-plus strain, E. coli C 3000. In sewage lagoons all three coliphages were consistently present and FRNA usually outnumbered both FDNA and somatic coliphages. However, the ratios of FRNA to the other two coliphages were not numerically large. Ratios of coliphages, especially of FRNA: FDNA, seem a promising toot to distinguish between human and animal faecal pollution. Overall, there were no strong correlations between the bacterial indicators and the coliphages. [TOP OF PAGE]
Lytic infection of Escherichia coli biofilms by bacteriophage T4. Doolittle, M.M., Cooney, J.J., Caldwell, D.E. (1995). Canadian Journal of Microbiology 41:12-18. Escherichia coli 3000 XIII formed biofilms on the surface of polyvinylchloride coupons in a modified Robbins device. Bacteriophage T4D+ infected cells in the biofilm and replicated. It is commonly held that bacteriophage cannot infect surface- attached bacteria (biofilms) because such bacteria are protected by an exopolymeric matrix that binds macromolecules and prevents their diffusion into the biofilm. To our knowledge this is the first observation that a bacteriophage can infect and multiply within cells growing as a biofilm. [TOP OF PAGE]
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]
A Starter Culture Rotation Strategy Incorporating Paired Restriction/Modification and Abortive Infection Bacteriophage Defenses in a Single Lactococcus lactis Strain. Durmaz, E., Klaenhammer, T.R. (1995). Appl. Environ. Microbiol. 61:1266-1273. Three derivatives of Lactococcus lactis subsp. lactis NCK203, each with a different pair of restriction/modification (R/M) and abortive infection (Abi) phage defense systems, were constructed and then rotated in repeated cycles of a milk starter culture activity test (SAT). The rotation proceeded successfully through nine successive SATs in the presence of phage and whey containing phage from previous cycles. Lactococcus cultures were challenged with 2 small isometric-headed phages, vphi-31 and ul36, in one rotation series and with a composite of 10 industrial phages in another series. Two native lactococcal R+/M+ plasmids, pTRK68 and pTRK11, and one recombinant plasmid, pTRK308, harboring a third distinct R/M system were incorporated into three NCK203 derivatives constructed separately for the rotation. The R+/M+ NCK203 derivatives were transformed with high-copy-number plasmids encoding four Abi genes, abiA, abiC, per31, and per50. Various Abi and R/M combinations constructed in NCK203 were evaluated for their effects on cell growth, level of phage resistance, and retardation of phage development during repeated cycles of the SAT. The three NCK203 derivatives chosen for use in the SAT exhibited additive effects of the R/M and Abi phenotypes against sensitive phages. In such combinations, phage escaping restriction are prevented from completing their infective cycle by an abortive response that kills the host cell. The rotation series successfully controlled modified, recombinant, and mutant phages which were resistant to any one of the individual defense systems by presenting a different set of R/M and Abi defenses in the next test of the rotation. [TOP OF PAGE]
Bacteriophages of Erwinia carotovora and Erwinia ananas isolated from freshwater lakes. Eayre, C.G., Bartz, J.A., Concelmo, D.E. (1995). Plant Disease 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]
Nodulation of Vicia faba plants by Rhizobium leguminosarum biovar Viciae raised in modified tube culture containing active transducing phages. El-Didamony, G. (1995). Egyptian Journal of Botany 35:163-176. Rhizobium leguminosarum biovar Viciae s (local strain) successfully formed nodules with Vicia faba plants which were raised in modified tube culture containing active phages. Susceptibility test indicated that, some of the isolated rhizobia from these nodules were phage-resistant, while the others were still sensitive Lysogenic strain formed by phage RLZ13 was able to form nodules containing rhizobia resistant to all tested phages.Some of these phages were also able to transduce the antibiotic marker from mutant local strain (str+ & nif+) to wild one (str- & nif-). [TOP OF PAGE]
Partial characterization of Streptomyces phages isolated from the soils of jarrah forest in Western Australia. El-Tarabily, K.A., Kurtboke, D.I., Hardy, G.E.S. (1995). Actinomycetes 6:7-15. [TOP OF PAGE]
Evolution: A composite model. Emiliani, C. (1995). Evolutionary? Therory 10:299-303. [TOP OF PAGE]
Detection of F+ bacteriophage in large volumes of water by a membrane filter method (MFM). Erb, P., Nasser, A.M., Fattal, B. (1995). Water Science and Technology 31:211-214. [TOP OF PAGE]
The evolution of virulence: A unifying link between parasitology and ecology. Ewald, P.W. (1995). Journal of Parasitology 81:659-669. [TOP OF PAGE]
Can phage defence maintain colicin plasmids in Escherichia coli? Feldgarden, M., Golden, S., Wilson, H., Riley, M.A. (1995). Microbiology 141:2977-2984. We examined the role of plasmid-based phage defence in maintaining plasmids, using colicin plasmids in Escherichia coli as a model system. Experimental data indicated that the possession of a colicin plasmid can confer limited protection against bacteriophages. A continuous culture model, using these experimental values, indicated that the observed limited protection alone could selectively maintain colicin plasmids, without requiring a competitive advantage due to colicinogeny. Phage defence might explain the current maintenance of colicin plasmids, given the naturally occurring high levels of resistance to colicins. This model also suggests that many plasmids might be maintained in natural populations, in part, by phage resistance, including 'cryptic' plasmids for which no phenotype is known. [TOP OF PAGE]
Bacteriophage resistance in Lactococcus: characterization of the ScrFI restriction/modification system from Lactococcus lactis subsp. cremoris UC503. Fitzgerald, G.F., Twomey, D.P., Daly, C., Coffey, A. (1995). pp. 581-590. In In Ferretti, J., Gilmore, M., Klaenhammer, T., and Brown, F. (eds.), Genetics of streptococci, enterococci and lactococci. Karger, Basel. [TOP OF PAGE]
Phage infection, transfection and transformation of Mycobacterium avium complex and Mycobacterium paratuberculosis. Foley-Thomas, E.M., Whipple, D.L., Bermudez, L.E., Barletta, R.G. (1995). Microbiology 141 ( Pt 5):1173-1181. Mycobacterium avium complex strains and Mycobacterium paratuberculosis are closely related intracellular pathogens affecting humans and animals. M. avium complex infections are a leading cause of morbidity and mortality in AIDS patients, and M. paratuberculosis is the agent of Johne's disease in ruminants. Genetic manipulation of these micro-organisms would facilitate the understanding of their pathogenesis, the construction of attenuated vaccine strains and the development of new drugs and treatment methods. This paper describes the replication of mycobacterial shuttle phasmids and plasmids, and the expression of the firefly luciferase reporter gene in M. avium complex and M. paratuberculosis. The mycobacteriophage TM4 propagated on M. smegmatis or M. paratuberculosis plaqued at the same efficiency on these two mycobacterial hosts. Screening of M. avium complex and M. paratuberculosis clinical isolates with TM4-derived luciferase reporter phages demonstrated that the majority of these isolates were susceptible to TM4. Conditions for introduction of DNA were determined by transfection of M. paratuberculosis with TM4 DNA and applied to isolate kanamycin-resistant transformants of M. avium complex and M. paratuberculosis with Escherichia coli-Mycobacterium shuttle plasmids. Recombinant plasmids were recovered from transformants without apparent loss of DNA sequences. These results provide the basis for the genetic manipulation of these pathogenic mycobacterial species. [TOP OF PAGE]
Evaluation of Serratia marcescens bacteriophage as a tracer and a model for virus removal in waste stabilisation ponds. Frederick, G.L., Lloyd, B.J. (1995). Water Science and Technology 31:291-302. [TOP OF PAGE]
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]
Phagotherapy of nosocomial strains of P. aeruginosa, belonging to the o-groups. Gabisonia, T.G., others??? (1995). Georg. Med. News. (I suspect this is "Georgia Medical News" and I also suspect this is Georgia as in the former USSR) N.15:19-21. [TOP OF PAGE]
The Revenge of the Germs, or Just Keep Inventing New Drugs. Garrett, L. (1995). p. ???-??? AnonymousThe Coming Plague: Newly Emerging Diseases in a World Out of Balance. ???, ??? [TOP OF PAGE]
Cloning and DNA sequence analysis of two abortive infection phage resistance determinants from the lactococcal plasmid pNP40. Garvey, P., Fitzgerald, G.F., Hill, C. (1995). Appl. Environ. Microbiol. 61:4321-4328. The lactococcal plasmid pNP40, from Lactococcus lactis subsp. lactis biovar diacetylactis DRC3, confers complete resistance to the prolate-headed phage vphi-c2 and the small isometric-headed phage vphi-712 in L. lactis subsp. lactis MG1614. A 6.0-kb NcoI fragment of pNP40 cloned in the lactococcal Escherichia coli shuttle vector pAM401 was found to confer partial resistance to vphi-712. Subcloning and deletion analysis of the recombinant plasmid pPGO1 defined a 2.5-kb ScaIHpaI fragment as conferring phage insensitivity. Sequence analysis of this region confirmed the presence of two overlapping open reading frames (ORFs). Further subcloning of pNP40 to characterize the resistance determinant active against vphi-c2 identified a 5.6-kb EcoRV fragment of pNP40 which, when cloned in pAM401, conferred partial resistance to both vphi-c2 and vphi-712. Subcloning and deletion analysis of the recombinant plasmid pCG1 defined a 3.7-kb EcoRV-XbaI fragment as encoding phage insensitivity. DNA sequence analysis of this region revealed the presence of a single complete ORF. The introduction of a frameshift mutation at the unique BglII site within this ORF disrupted the phage resistance phenotype, confirming that this ORF is responsible for the observed phage insensitivity. The mechanisms encoded by pPGOI and pCGI in L. lactis subsp. lactis MG1614 conformed to the criteria defining abortive infection and were designated AbiE and AbiF, respectively. Analysis of the phage DNA content of vphi-712-infected hosts containing AbiF demonstrated that it inhibited the rate of phage DNA replication, while AbiE had little effect on phage DNA replication, suggesting a later target of inhibition. The predicted protein product of abiF shows significant homology to the products of two other lactococcal abortive infection genes, abiD and abiD1. [TOP OF PAGE]
Molecular genetics of bacteriophage and natural phage defence systems in the genus Lactococcus. Garvey, P., van Sinderen, D., Twomey, D.P., Hill, C., Fitzgerald, G.F. (1995). International Dairy Journal 5:905-947. Bacteriophage infection of starter cultures used in a range of milk fermentation processes, particularly those involving Lactococcus lactis, poses a significant problem in industrial practice. The application of genetic and molecular technologies to the study of lactococcal bacteriophages has proven to be very rewarding in terms of understanding the nature of phage with respect to their physical and genetic organisation. The availability of the full genomic sequence of a number of phages provides an unambiguous basis for determining the relationship between them, for elucidating their evolutionary progression and will also yield strategies for obstructing successful phage proliferation on previously sensitive hosts. The genetic analysis of phage/host interactions has also highlighted the presence of natural defence systems (e.g. adsorption blocking, inhibition of phage DNA entry, restriction modification and abortive injection) in lactococci. A number of restriction modification systems and abortive infection mechanisms have been characterized at a molecular level and the genes involved have been cloned and sequenced. Plasmid-encoded phage resistance mechanisms can be exploited to generate strains which can successfully counter phage proliferation and will provide a basis for understanding the complex interactions between phages and their target hosts at a molecular level. [TOP OF PAGE]
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]
Occurrence of Propionibacterium freudenreichii bacteriophages in swiss cheese. Gautier, M., Rouault, A., Sommer, P., Briandet, R. (1995). Appl. Environ. Microbiol. 61:2572-2576. We isolated bacteriophages active against Propionibacterium freudenreichii from 16 of 32 swiss cheese samples. Bacteriophage concentrations ranged from 14 to 7 x 10(5) PFU/g, depending on the sample and the sensitive strain used for detection. Only a few strains, 8 of the 44 strains of P. freudenreichii in our collection, were sensitive. We observed that multiplication of bacteriophages occurred in the cheese loaf during multiplication of propionibacteria in a warm curing room, but it seems that these bacteriophages have no adverse effect on the development of the propionic flora. We also found that sensitive cells, originating from either the starter or the cheese-making milk, were present at a high level (10(9) CFU/g) in the cheese. [TOP OF PAGE]
Mutual adaptation of bacteriophage fd, pfd plasmids and their host strains. Geider, K., Baldes, R., Bellemann, P., Metzger, M., Schwartz, T. (1995). Microbiological Research 150:337-346. The synthetic plasmid pfdC1 with the replication origin of phage fd and fd gene 2 grows autonomously in E. coli cells. DNA sequencing revealed several mutations compared to the fd genome causing reduced expression of viral gene 2 protein, which can be toxic for the host cell. Another adaptation was noticed for E. coli strains with a copy of fd gene 2 on the F-episome and a pfdA-plasmid with a minimal fd replication origin, when maintained at 42 degree C. The carrier cells adjusted their cellular metabolism to these stress conditions, whereas replication functions of the plasmid or expression of fd gene 2 on the F-episome were not changed. The filamentous bacteriophages tend to reduce their genome size into miniphages, which was also observed for phages with an antibiotic resistance gene. Bacteriophages with a transposon insertion in the viral gene 2 had a tendency to restore the mutated gene by exchange with the functional gene 2 carried in recA-host cells. Mobilization of pfd- plasmids with RP4 transfer functions was reduced due to interference of replication and transfer in the rolling circle mode. The vectors used in these studies can also be applied as cloning vectors, which are compatible with many other plasmid vectors. [TOP OF PAGE]
Reverse transcription PCR to detect enteroviruses in surface water. Gilgen, M., Wegmuller, B., Burkhalter, P., Buhler, H.P., Muller, U., Luthy, J., Candrian, U. (1995). Appl. Environ. Microbiol. 61:1226-1231. [TOP OF PAGE]
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]
Bacterioides fragilis and Escherichia coli bacteriophages—Excretion by humans and animals. Grabow, W.O.K., Neubrech, T.W., Holtzhausen, C.S., Jofre, J. (1995). Water Science & Technology 31:223-230. [TOP OF PAGE]
Efficiency of the Euroguard domestic water treatment unit with regard to viruses, phages and bacteria. Grabow, W.O.K., Wyn-Jones, A.P., Schildhauer, C., Jofre, J. (1995). Water S A (Pretoria) 21:71-74. The reduction in numbers of human viruses as well as bacteria and phages in water treated by the commercial Euroguard water filtercum-purifier for the domestic treatment of drinking water was evaluated. Drinking water seeded with laboratory strains of viruses, bacteria and phages which indicate faecal pollution, as well as sewage-contaminated river water and secondary treated waste water containing naturally occurring organisms, were passed through the unit which consists of a candle prefilter, activated carbon filter and ultraviolet irradiation compartment. At the prescribed flow rate of not more than 1 l cntdot min-1, numbers of poliovirus, hepatitis A virus, adenovirus types 40 and 4 1, rotavirus SA11, human rotavirus, coliphage MS2, somatic coliphages, Escherichia coli, Streptococcus faecalis, Clostridium perfringens, total coliform bacteria, faecal streptococci and the heterotrophic plate count were reduced by more than 99.99% in all waters tested. In all test runs, including those on secondary waste water which was not intended to be used in the unit and represents a "worst-case" situation in practice, the quality of the treated water was well within microbiological limits of international specifications for drinking water. [TOP OF PAGE]
Seasonality and extinction in chaotic metapopulations. Grenfell, B.T., Bolker, B.M., Kleczkowski, A. (1995). Proc. R. Soc. Lond. B 259:97-103. A body of recent work has used coupled logistic maps to show that these model metapopulations show a decrease in global extinction rate in the chaotic region of model behaviour. In fact, many of the main ecological candidates for low-dimensional chaos are continuous-time host-parasite and predator-prey systems, driven by strong seasonal forcing of one or more population parameters. This paper, therefore, explores the relation between seasonal forcing and metapopulation extinction for such systems. We base the analysis on extensive simulations of a stochastic metapopulation model for measles, based on a standard compartmental model, tracking the density of susceptible, exposed, infectious and recovered individuals (the SEIR model). The results show that, by contrast with coupled logistic maps, the increased seasonality which causes chaos maintains or increases levels of global extinction of infection, by increasing the synchrony of sub-population epidemics. The model also illustrates that the population interaction (here between susceptible and infective hosts) has a significant effect on patterns of synchrony and extinction. [TOP OF PAGE]
Characterization of Serratia entomophila bacteriophages and the phage-resistant mutant strain BC4B. Grkovic, S., O'Callaghan, M., Mahanty, H.K. (1995). Appl. Environ. Microbiol. 61:4160-4166. Successful large-scale fermentations of the bacterium Serratia entomophila for use in biological control of the soil-dwelling insect Costelytra zealandica has required the development of a phage-resistant mutant, BC4B. We report our investigations into S. entomophila phages and the nature of the phage resistance mechanism of strain BC4B. The parental strain of BC4B, A1M02, was found to contain two previously unidentified prophages, vphi-9A and vphi-9B, which were UV inducible and also released spontaneously in large numbers. BC4B was shown to be completely cured of vphi-9A. Single lysogens of vphi-9A and vphi-9B were not homoimmune to any other S. entomophila phages. However, on the basis of DNA-DNA homology, all S. entomophila phages except vphi-CW3 were shown to have significant regions of homology and also packaged their DNA via pac-like mechanisms. The failure of phage particles to adsorb was identified as the basis of phage resistance in BC4B. In addition, it was demonstrated that all known S. entomophila phages are naturally temperature sensitive. [TOP OF PAGE]
Extremo-phage: In vitro selection of tolerance to a hostile environment. Gupta, K., Lee, Y., Yin, J. (1995). J. Mol. Evol. 41:113-114. Extremophiles are microorganisms that thrive under extreme conditions such as temperatures above 65 degree C, pHs below 4 or above 10, salt concentrations above 0.5 M, or pressures of 600 atm. While studies of enzymes either isolated from extremophiles, or generated using site-specific mutagenesis, or adapted by in vivo or in vitro selection have established a precedent for the engineering and application of proteins at extreme conditions, generalization of the approaches to more complex multimolecular or multitask systems has remained elusive. Here we demonstrate that a significantly more complex system-a bacteriophage-can over a number of generations be adapted to tolerate a hostile and unnatural environment. An in vitro selection strategy was used to adapt phage to urea, a protein denaturing agent. As the concentration of urea employed in selections over 20 generations was gradually increased from 5 to 9 m, the surviving phages steadily improved their tolerance, finally achieving a greater than 350-fold stability enhancement over the original population. [TOP OF PAGE]
Comparing predator-prey models to Luckinbill's experiment with Didinium and Paramecium. Harrison, G.W. (1995). Ecology 76:357-374. When Leo Luckbill (1973) grew Paramecium aurelia together with its predator Didinium nasutum in 6 ml of standard cerophyl medium, the Didinium consumed all the prey in a few hours. When the medium was thickened with methyl cellulose, the populations went through two or three diverging oscillations lasting several days before becoming extinct. When he used a half-strength cerophyl medium thicked with methyl cellulose, the populations maintained sustained oscillations for 33 d before the experiment was terminated. The data from this experiment provide a rare opportunity to test current predator-prey models. ¶ A standard differential equation predator-prey model with a carrying capacity for the prey and a saturating (Type 2) functional response predicts the outcome of Luckinbill's experiment qualitatively, but does not give a good quantitative fit to the data. Several modifications of this model are tested against the data for the populations grown in the medium thickened with methyl cellulose, using the Marquardt-Levenberg method to obtain the least squares best fit. Neither Leslie type models nor models with a ratio-dependent functional response do well, but adding either predator mutual interference or a sigmoid (Type 3) functional response improves fit dramatically. Modeling the predator growth rate to depend on energy or nutrient storage instead of directly on the rate of consumption of prey, thus creating a delayed numerical response, along with predator mutual interference or a sigmoid functional response, produced the best models and gave excellent fits to the data. These models are further validated by the fact that changing only one or two parameter values to reflect the unthickened medium or the half-strength medium also gives reasonably good fits to the other two data sets. The last model requires a more sigmoid functional response to fit the data in the thickened than in the unthickened medium, suggesting that an increase in the cost-benefit ratio of energy spent searching to energy gained capturing prey inhibits the predator searching at low prey densities. [TOP OF PAGE]
Removal and inactivation of viruses by drinking-water treatment process under full-scale conditions. Havelaar, A.H., Vanolphen, M., Schijven, J.F. (1995). Water Science & Technology 31:55-62. [TOP OF PAGE]
Study on Pseudomonas aeruginosa Cytotoxin and Cytotoxin-Converting Phages. Hayashi, T. (1995). Japanese Journal of Bacteriology 50:391-401. [TOP OF PAGE]
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]
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-µm 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 > 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]
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 >10⁶ bacteria ml^-1, but to which host cells were not added. Host cells that were added to natural seawater were quantified with 99 ± 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 (<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]
Isolation of FC3-11, a bacteriophage specific for the Klebsiella pneumoniae porin OmpK36, and its use for the isolation of porin-deficient mutants. Hernandez Alles S, Alberti, S., Rubires, X., Merino, S., Tomas, J.M., Benedi, V.J. (1995). Canadian Journal of Microbiology 41:399-406. FC3-11, a bacteriophage specific for the Klebsiella pneumoniae porin OmpK36, was isolated by its ability to infect Escherichia coli strains expressing the cloned OmpK36 porin. Porin OmpK36 was shown to be the receptor for phage FC3-11 by the observations that K. pneumoniae and E. coli strains that do not express OmpK36 were resistant to phage FC3-11, the purified porin inactivated the phage, and mutants selected for FC3-11 resistance had lost OmpK36. The outer membrane protein OmpK35 was isolated from a K. pneumoniae phage-resistant mutant by using porin isolation methods and was shown to contain an N-terminal sequence typical of enterobacterial porins. Bacteriophage FC3-11, alone or in combination with previously described lipopolysaccharide-specific phages, is a valuable tool to obtain OmpK36-porinless mutants. [TOP OF PAGE]
Characterization of Lactococci other than Lactococcus lactis for Possible Use as Starter Cultures. Holler, B.J., Steele, J.L. (1995). International Dairy Journal 5:275-289. The objective of this study was to examine lactococcal species other than Lactococcus lactis ssp. lactis and Lactococcus lactis ssp. cremoris for their ability to serve as starter cultures. To identify the most promising cultures, resistance to L. lactis-derived bacteriophage, lack of inhibitor production, ability to metabolize lactose, and acid production in milk supplemented with glucose and casein hydrolysate were examined. The results of these analyses lead to three L. raffinotactis strains being chosen for further characterization. The L. raffinolactis strains were determined to: produce acceptable levels of acetaldehyde and diacetyl; be incapable of growth at 40 degree C; survive eight growth cycles against laboratory and industrial phage cocktails; contain one or no plasmids; and lack a caseinolytic proteinase. A plasmid expressing the Lactococcus lactis ssp. cremoris Wg2 caseinolytic proteinase was introduced into L. raffinolactis 617; however, no detectable caseinolytic proteinase activity was observed in the resulting transformants. [TOP OF PAGE]
Small extrachromosomal nucleic acid segments in protozoan parasites. Hotzel, I., Kabakoff, R., Ozaki, L.S. (1995). Veterinary Parasitology 57:57-60. Viruses have been described in the following protozoa: Babesia spp., Trichomonas vaginalis, Giardia lamblia, Leishmania braziliensis and Eimeria spp. In order to study the Babesia bovis virus, merozoites have been prepared from the blood of infected cattle. Agarose gel electrophoresis of nucleic extracts from the bovine protozoa B. bovis and Babesia bigemina were separated into genomic DNA and at least two additional nucleic acids. One molecule with a relative mobility of 5.5 kilobase pairs (kbp) was identified as a double-stranded RNA virus-like particle. Another 6.2 kbp DNA molecule had sequences related to mitochondrial genome. [TOP OF PAGE]
Genotyping male-specific RNA coliphages by hybridization with oligonucleotide probes. Hsu, F.-C., Shieh, Y.-S.C., van Duin, J., Beekwilder, M.J., Sobsey, M. (1995). Appl. Environ. Microbiol. 61:3960-3966. [TOP OF PAGE]
Mitomycin C induction of bacteriophages from Serpulina hyodysenteriae and Serpulina innocens. Humphrey, S.B., Stanton, T.B., Jensen, N.S. (1995). FEMS Microbiol. Let. 134:97-101. A prophage was induced from cells of the pathogenic spirochaete Serpulina hyodysenteriae using mitomycin C. Five to seven hours after mitomycin C was added (8 mu-g/ml, final concentration) to S. hyodysenteriae B204 cultures in BHIS broth (OD-620 = 0.9) cell lysis was detected as a decrease in culture optical density. Bacteriophage particles attached to whole cells and to cell debris were detected by electron microscopic analysis of negatively stained (2% PTA, pH 7.0) bacteria harvested by centrifugation from mitomycin C treated cultures. The phage particles consisted of a head (45 nm diameter) and a tail (64 nm times 9 nm). Bacteria from untreated cultures lacked phages detectable by electron microscopy. The appearance of bacteriophage particles in mitomycin C treated cultures correlated with the appearance of extrachromosomal DNA, 7-8 kb in size as estimated by agarose gel electrophoresis, in DNA preparations from treated S. hyodysenteriae cells. When cultures of other S. hyodysenteriae strains (B78, B169, A-1, B8044, B6933. Ack300/8, R-1) and S. innocens 4/71 in BHIS were treated with mitomycin C (8-15 mu-g/ml, final concentration), phages similar in morphology and size to the S. hyodysenteriae B204 phage were induced. [TOP OF PAGE]
[Does taxis exist in bacterial viruses?]. [Review] [Russian]. Ivanitskii, G.R., Medvinskii, A.B., Deev, A.A., Khusainov, A.A., Tsyganov, M.A. (1995). Biofizika 40:60-73. By way of example of interaction of T4 bacteriophage with E. coli bacterium the scenario of enhancement of sorption of phages on bacteria through the remote mechanism of their cyclic interaction has been considered. An enlargement of the typical phage size, when its fibrillae are opened, underlies this mechanism. Modification of the structure of phages also occurs through the medium by release of products of bacterial metabolism into it. Allied questions related to investigation of physicochemical and biological processes, which require to take into account "fluffing" of microparticles. The medium-induced change of volume of microparticles leads to spatial cooperative effects with non-linear dynamics. Such phenomena are possible in all diffusional processes in biology, chemistry and physics. [TOP OF PAGE]
Baseplate as a logical controller between the reception and the transformation of bacteriophage T4. Ivanitskii, G.R., Khusainov, A.A., Deev, A.A., Dawson, K. (1995). Biofizika 40:1265-1280. It has been shown that the complex functioning of the baseplate of the bacteriophage T4 is based on the high level hierarchy in the structure organization and on the interaction of protein components forming the hub and the "channels" of short and long fibers. The presence of structure proteins with stabilizing and destabilizing functions has been revealed. It has been shown that the process of binding of long tail fibers with cell receptors is a cooperative process. In general the baseplate can be considered as a logic module providing the transition from the adsorption to the nonreversible reorganization in the bacteriophage functioning. [TOP OF PAGE]
Evaluation of indicators for assessment of human and animal faecal pollution of surface run-off. Jagals, P., Grabow, W.O.K., De Villiers, J.C. (1995). Water Science and Technology 31:235-241. [TOP OF PAGE]
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]
Isolation and characterization of a temperate bacteriophage from a ruminal acetogen. Jiang, W.H., Patterson, J.A., Steenson, L.R. (1995). Current Microbiology 31:336-339. Nine acetogenic bacterial cultures recently isolated from the bovine rumen were tested for phage susceptibility by plaque formation. Both clear plaques and plaques with turbid centers were occasionally seen, but could not be used repeatedly to lyse pure cultures of acetogens, suggesting the possibility of a temperate phage. Five of the nine acetogenic isolates showed a response to mitomycin C induction. Acetogenic isolate H3HH was chosen for further study because it produced the greatest lysogenic response to mitomycin C. The bacteriophage was induced with mitomycin C, examined by transmission electron microscopy, and shown to have a hexagonal head (diameter, 59 eta-m), a long flexible tail (192 eta-m), and a flat collar (diameter, 31 eta- m). The bacteriophage was classified within Bradley's group B. Bacteriophage DNA was determined to contain 36.2 kilobases of linear double-stranded DNA. [TOP OF PAGE]
Bacteriophage removal in water-treatment plants. Jofre, J., Ollé, E., Ribas, F., Vidal, A., Lucena, F. (1995). Water Science & Technology 31:69-73. [TOP OF PAGE]
Potential usefulness of bacteriophages that infect Bacteroides fragilis as model organisms for monitoring virus removal in drinking water treatment plants. Jofre, J., Olle, E., Ribs, F., Vidal, A., Lucena, F. (1995). Appl. Environ. Microbiol. 61:3227-3231. The presence of bacteriophages at different stages in three drinking water treatment plants was evaluated to study the usefulness of phages as model organisms for assessing the efficiency of the processes. The bacteriophages tested were somatic coliphages, F-specific coliphages, and phages infecting Bacteroides fragilis. The presence of enteroviruses and currently used bacterial indicators was also determined. Most bacteriophages were removed during the prechlorination- flocculation-sedimentation step. In these particular treatment plants, which include prechlorination, phages were, in general, more resistant to the treatment processes than present bacterial indicators, with the exception, in some cases, of clostridia. Bacteriophages infecting B. fragilis were found to be more resistant to water treatment than either somatic or F-specific coliphages or even clostridia. Enteric viruses were found only in untreated water in low numbers, and consequently, the efficiency of the plants in the removal of viruses could not be evaluated with precision. The numbers and frequencies of detection of the various microorganisms in water samples taken in the distribution network served by the three plants confirm the results found in the finished water at the plants. [TOP OF PAGE]
Association between the mollusc bivalve Loripes lucinalis and a Chlamydia-like organism, with comments on its pathogenic impact, life cycle and possible mode of transmission. Johnson, M.A., Le Pennec, M. (1995). Marine biology. Berlin 123:523-530. Loripes lucinalis is a littoral bivalve which has already been confirmed to harbour endo-cellular sulfur-oxidizing bacteria within its gills. Examination of the digestive gland of L. lucinalis collected from the Moulin Blanc Beach in the Bay of Brest (Brittany, France) revealed the existence of an additional association involving a Chlamydia-like organism. Three different forms of Chlamydia-like bacteria were observed: reticulate rod-shaped cells, electron-dense cells and enlarged cells. The reticulate rod-shaped cells and the electron-dense bodies are thought to represent the germinal initial body and infectious form of the bacteria, respectively. The enlarged cells were always associated with what are believed to be spherical or icosahedral phages. Initial infestation seems to occur by phagocytosis at the apical pole of the digestive cells of the tubule and duct epithelia. Within the host cell, the bacteria undergo binary fission and budding, forming an inclusion which gradually fills up the cell. Inclusions are generally between 15 and 30 mu m in size, and >85% of all individuals examined possessed inclusion bodies. The level of infestation varied between individuals, some being heavily colonized, but did not seem to be related to season. Histological and ultrastructural observations suggest that, once developed, the colony has three possible fates: (1) the cells will degenerate due to phage infection; (2) colony overcrowding will occur, causing the development of electron-dense bodies that will be released into the lumen; (3) the entire membrane-bound inclusion will be released into the lumen and subsequently into the pallial cavity. Inclusions within the pallial cavity may be ingested by the host or may even be phagocytized by bacteriocyte cells of the gill. It is proposed that this association could be a form of symbiosis and that L. lucinalis may, therefore, be a rare example of an organism adapted to harbour two very different symbioses. [TOP OF PAGE]
Inactivation of Lactobacillus bacteriophage PL-1 by microwave irradiation. Kakita, Y., Kashige, N., Murata, K., Kuroiwa, A., Funatsu, M., Watanabe, K. (1995). Microbiology and Immunology 39:571-576. The effect of microwave irradiation on the survival of bacteriophage PL-1, which is specific for Lactobacillus casei, was studied using a commercial 2,450 MHz microwave oven. The phages were inactivated by microwave irradiation according to almost first-order reaction kinetics. The rate of phage inactivation was not affected by the difference in the continuous or intermittent irradiation, nor by the concentrations of phages used, but was affected by the volume of phage suspensions, which prevented the loss of generated heat. Microwave irradiation of phage suspensions produced a number of ghost phages with empty heads, but fragmentation of the tail was hardly noticed. The breakage of phage genome DNA was primarily caused by the heat generated by microwave irradiation, whereas the phage DNA was not affected by the same temperature achieved by heat from outside. Thus we concluded that the phage-inactivating effect of microwave irradiation was mainly attributed to a thermal microwave effect, which was much stronger than a simple thermal exposure. [TOP OF PAGE]
[Viruses of parasitic protozoa]. [Polish]. Kasprzak, W., Majewska, A.C. (1995). Wiadomosci Parazytologiczne 41:131-137. The authors present the actual review on several publications concerning the molecular characterizations of the viruses found in parasitic protozoa such as Giardia, Trichomonas, Leishmania and Entamoeba histolytica. All of the RNA viruses observed in parasitic protozoa showed several similarities and did not considerably differ from the viruses found in simple eukaryotic cells; they closely correspond to dsRNA viruses of yeast. The supposition that the protozoan symbionts detected in laboratories transfer to their hosts in natural conditions seemed to be rational, though, there are no evidences that these symbionts are potential pathogens. However, the opinion reiterates that intestinal protozoa (e.g. Entamoeba histolytica) may serve as vectors for HIV or cofactors of HIV infection. The authors point out that irrespective of the potential role of viruses as vectors in the transfection system for parasitic protozoa, the observed viral system constitutes an unusual experimental system to solve the problems of gene expression. [TOP OF PAGE]
[Viruses of parasitic protozoa]. Kasprzak, W., Majewska, A.C. (1995). Wiadomosci Parazytologiczne 41:131-137. The authors present the actual review on several publications concerning the molecular characterizations of the viruses found in parasitic protozoa such as Giardia, Trichomonas, Leishmania and Entamoeba histolytica. All of the RNA viruses observed in parasitic protozoa showed several similarities and did not considerably differ from the viruses found in simple eukaryotic cells; they closely correspond to dsRNA viruses of yeast. The supposition that the protozoan symbionts detected in laboratories transfer to their hosts in natural conditions seemed to be rational, though, there are no evidences that these symbionts are potential pathogens. However, the opinion reiterates that intestinal protozoa (e.g. Entamoeba histolytica) may serve as vectors for HIV or cofactors of HIV infection. The authors point out that irrespective of the potential role of viruses as vectors in the transfection system for parasitic protozoa, the observed viral system constitutes an unusual experimental system to solve the problems of gene expression. [TOP OF PAGE]
[The bacteriophage lysis-susceptibility properties of Vibrio cholerae strains isolated in separate regions of Dagestan in 1994]. [Russian]. Kazakova, E.S., Abramova, E.G., Makkaeva, A.M., Luk'ianova, O.I., Naumov, A.V., Adamov, AK (1995). Zhurnal Mikrobiologii, Epidemiologii i Immunobiologii Suppl 2:78-80. The study of the properties of V. cholerae strains isolated in June-September 1994 in the Daghestan revealed that they belonged, according to their specific properties, to typical representatives of V. eltor, serovar Ogawa, but a great part of them (67.2%) was not lysed by diagnostic cholera bacteriophages. Experiments with different batches of diagnostic cholera bacteriophages showed the necessity of their further improvement. [TOP OF PAGE]
Viral inactivation by potassium ferrate. Kazama, F. (1995). Water Science and Technology 31:165-168. [TOP OF PAGE]
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]
Reduction of the concentration of bacteria and coliphages along the flowing stretch of a treated sewage channel. Koerner, S., Dizer, H., Lopez-Pila, J.M. (1995). Acta Hydrochimica et Hydrobiologica 23:264-270. The efficiency of surface waters to eliminate E. coli, fecal streptococci, Salmonella spp., and coliphages was evaluated in a small river which receives treated wastewater and which is rich in submerged macrophytes. The study took place between April and December, 1994. Total colony count, BOD-5, O-2 concentration and water temperature were determined in the river as well. As the river does not receive additional water downwards along its 17.2 km course, dilution effects could be ruled out as the cause for the elimination of the microorganisms. The reduction is assumed to happen rather due to sedimentation, grazing, and adsorption to the submerged waterplants. Immediately after discharge of the wastewater, the river water contained about 10-5 cfu/ 100 mL E. coli and 10-4 cfu/ 100 mL fecal streptococci, about 1000 pfu/100 mL coliphages, and, as a rule, was positive for salmonella in 10 mL. The reduction of E coli, fecal streptococci, salmonella, clostridia, and coliphages at the end of the course was 1 to 2 orders of magnitude. This reduction took place mainly within the first 4.7 km, a part in which, due to low flowing velocities. suspended solids settle down efficiently. Besides, at the end of this part the submerged waterplants are especially abundant. The reduction of suspended solids correlated positively with that of BOD-5, bacteria. and coliphages. The reduction of microorganisms was not sufficient to fulfill the requirements of the European Community guidelines for bathing waters and for surface waters used as drinking water source. The regenerating capacity of surface waters is not sufficient to eliminate pathogens from conventionally treated wastewater. Therefore, tertiary treatment is necessary to keep receiving waters reasonably free from pathogens. [TOP OF PAGE]
Whole-virus vaccine development by continuous culture on a complementing host. Kong, D., Yin, J. (1995). Bio/Technology 13:583-586. We have evaluated an adaptive strategy for generating whole-virus vaccines using a bacteriophage model. Wildtype phage T7 was cultivated in a two-stage continuous stirred-tank reactor (CSTR) utilizing a recombinant E. coli host that constitutively expressed T7 RNA polymerase, an essential enzyme of the early viral metabolism. Over the course of 180 generations a diversity of phage variants emerged, outgrew the wildtype, and were subsequently eclipsed by yet fitter variants, based on host-ranges, restriction patterns, and one-step growth responses of isolated clones. The fittest variant, which required complementation by the recombinant host in order to grow, deleted at least 12 percent of its genome and replicated twice as fast as the wildtype. Moreover, this variant was immunogenically indistinguishable from the wildtype, based on cross-reactivities of antisera raised against both. These results suggest the feasibility of the proposed strategy for the development of safe whole-virus vaccines. [TOP OF PAGE]
The ecological concept of parasitism [Russian]. Krasnoshchekov, G.P. (1995). Zhurnal Obshchei Biologii 56:18-32. Analysis of morpho-ecological adaptations of parasites showed that their necessary and sufficient characteristic is their inhabiting the host environment. Integration with the environment is achieved 1) by adaptations towards a particular habitat (first order environment) at certain phases of onthogenesis, and 2) by adaptations to the aggregate of hosts, their ecology and factors regulating the numbers of parasites (second order environment) at the level of their entire life cycle. The evolutionary progress of parasites is sustained by the increase in their independence from extrinsic factors not by means of general organization complication and integration (as in free-living animals), but by elimination of free-living developmental stages and by increase of integration with the host environment. The basis of the latter is formed by ecological adjusting of parasites to the environment. It is achieved by syncytial transformation of the covers and the use of communication means analogous to those of host cells. The consequence of host-parasite integration is the transition of parasites from resource consumption to the management of the environment. It is manifested by their influence on defensive reactions and other functions of the organism, as well as on its behavior and ecology. Parasitism may turn into other forms of coexistence (commensalism, mutualism) in the course of coevolution, as a result of dialectical overcoming of antagonistic interactions of the two partners. [TOP OF PAGE]
Introduction of Pseudomonas aeruginosa mutator phage D3112 into Alcaligenes eutrophus strain CH34. Krylov, V., Merlin, C., Toussaint, A. (1995). Res. Microbiol. 146:245-250. We have investigated the possibility of growing mutator phages from Pseudomonas aeruginosa on various isolates of Alcaligenes eutrophus. Although none out of 10 A. eutrophus strains were susceptible to infection with any of the phages tested, phage D3112 could be readily transferred in our model strain CH34 by means of an RP4::D3112 plasmid. CH34/RP4::D3112 lysogenes were stable and produced phages. However, neither mitomycin C nor UV treatment increased the phage yield. [TOP OF PAGE]
Mucoid clones of Pseudomonas aeruginosa PAO1 surviving after induction of transposable prophages. Krylov, V.N., Solov'eva, T.I., Burkal'tseva, M.V. (1995). Genetika 31:1375-1379. The origin and properties of mucoid clones were studied. The clones were selected with high frequency after thermoinduction of Pseudomonas aeruginosa lysogenic for phage-transposons (PT). The production of alginate does not promote the survival of lysogenic bacteria at 42degreeC. Mucoid clones were shown to appear before thermoinduction; the frequency of their formation does not depend on the specificity of the mutator effect intrinsic to different PT. Phenotypic differences typical of mucoid clones can be mediated by different mutations promoting clone survival at 42degreeC an