Evolutionary Adaptation of an RNA Bacteriophage to Repeated Freezing and Thawing Cycles.

Bacteriophage fitness is determined by factors influencing both their replication within bacteria and their ability to maintain infectivity between infections. The latter becomes particularly crucial under adverse environmental conditions or when host density is low. In such scenarios, the damage experienced by viral particles could lead to the loss of infectivity, which might be mitigated if the virus undergoes evolutionary optimization through replication. In this study, we conducted an evolution experiment involving bacteriophage Qß, wherein it underwent 30 serial transfers, each involving a cycle of freezing and thawing followed by replication of the surviving viruses. Our findings show that Qß was capable of enhancing its resistance to this selective pressure through various adaptive pathways that did not impair the virus replicative capacity. Notably, these adaptations predominantly involved mutations located within genes encoding capsid proteins. The adapted populations exhibited higher resistance levels than individual viruses isolated from them, and the latter surpassed those observed in single mutants generated via site-directed mutagenesis. This suggests potential interactions among mutants and mutations. In conclusion, our study highlights the significant role of extracellular selective pressures in driving the evolution of phages, influencing both the genetic composition of their populations and their phenotypic properties.

Isolation and grouping of RNA phages by Itaru Watanabe et al. (1967).

I. Watanabe et al. isolated approximately 30 strains of RNA phages from various parts of Japan. To isolate RNA phages, they assessed the infection specificity of male Escherichia coli and RNase sensitivity. They found that the isolated strains of RNA phages could be serologically separated into three groups. Furthermore, most of them were serologically related, and the antiphage rabbit serum prepared by one of these phages neutralized most of the other phages. The only serologically unrelated phage was the RNA phage Qß, which was isolated at the Institute for Virus Research, Kyoto University, in 1961.

Study on the nucleic acid of E. coli bacteriophage with broad host range and its sterilization effect to sewage samples from the environment / 中华流行病学杂志

<p><b>OBJECTIVE</b>To study the change of nucleic acid sequence and the germicidal effect of an E. coli bacteriophage with broad host range isolated from hospital sewage as well as to study the mechanism of phage host specificity and the effect of killed bacteria by phage-disinfectant to the samples from sewage water.</p><p><b>METHODS</b>To extract the nucleic acid from phage f(2) and phage with broad host range using anti-serum-carbamidine hydrochloride assay. Purity with agarose gel electrophoresis was then evaluated. Differences of nucleic acid sequence between phage f(2) and phage with broad host range with reverse transcription-polymerase chain reaction (RT-PCR) and random amplified polymorphic DNA (RAPD)-PCR were also comparing and analysed. Through observing the germicidal test of phage f(2) and phage with broad host range to samples from environment, different sterilization effects between the two phages were compared.</p><p><b>RESULTS</b>Analystic test for nucleic acid revealed that the two phages both belonged to 6000 bp, single-stranded RNA bacteriophage. Significant differences in their specificity of RAPD-PCR and RT-PCR were found during the changed of host range; with 26 RAPD-cDNA differential fragments found that in two phages RAPD-PCR products. The RT-PCR product of phage f(2) was 450 bp cDNA fragment, but the phage with broad host range did not show PCR product. Treating the sewage water with phage under broad host range, the germicidal test showed that the cleaning rate of E. coli bacteria and phage f(2) in water samples from environment could reach 36.75% - 56.28%, 30.84% - 47.96%, 19.19% - 35.06% and 13.05% - 27.85%, respectively.</p><p><b>CONCLUSION</b>The cleaning rates to E. coli and bacteria by phage with broad host range were obviously higher than phage f(2) (P = 0.000). Analytic test for nucleic acid indicated that host-specific lytic effect of phage with broad host range had been changed at genetic level.</p>

Capacidad fagocítica de las células del exudado peritoneal de ratones inmunizados con una preparación ribosomal de Salmonella Typhi Ty2 / Phagocytic capacity of exudate peritoneal cells from mice immunized with Salmonella typhi Ty2 ribosomal fraction

Se comparó la capacidad fagocítica de células ael exudado peritoneal (CEP) de ratones CFW inmunizados con una preparación ribosomal de Salmonella typhi Ty2, con la de ratones protegidos con una vacuna de bacterias inactivadas por calor, ambas en relación con lo obtenido en animales testigo, no inmunizados. Los ribosomas se administraron subcutáneamente en una dosis inicial de 100 µg de ARN y se dio un refuerzo igual a los 14 días, ambos con adyuvantes incompleto de Freund (AIF). Los ratones inmunizados con vacuna de células muertas, recibieron una sola dosis subcutánea con 16***6 bacterias en AIF. Al cabo de 7, 11, 14, 18, 22, 25, y 31 días se indujeron y extrajeron las CEP de los animales de cada grupo e individualmente se cultivaron in vitro junto con S. Typhi Ty2 virulento no opsonizado en relación células-bacterias 1:200. La sobrevida de las bacterias fagocitadas se determinó a las 24 horas de cultivo: las CEP se romperon y por cuenta viable se enumeraron las bacterias no digeridas. Los resultados indican que las CEP de los inmunizados eliminan bacterias con mayor eficiencia que las de testigos. También se demostró que la eficiencia bactericida fue significativamente mayor (P máxima de 0.005) para las CEP de los ratones tratados con la fracción ribosomal que las CEP de los animales vacunados con bacterias intactas no viables. Fiebre tifoidea; vacuna ribosomal; inmunidad a Salmonella; Salmonella typi; fagocitosis por células peritoneales

A comparitive analysis of RNA coliphages: structural and regulatory features

Describes a comparative analysis of RNA coliphages with special emphasis on regulatory and structural features. Phylogenetic phage sequence comparison reveals kinship between different phages and facilitates deduction of their secondary structure. Complete sequences from phage fr and partial sequences from group I phages M12, R17 and f2 were determined. The nucleotide sequence from a serological intermediate JP34 was partially elucidated, Only the fr sequence proved suitable for comparison with MS2 (similarity 77 per cent). A "core" structure (3' terminal region) of phage RNA proposed a certain structural resemblance with tRNA. Comparison of the MS2 and fr nucleotide sequences revealed absence of an AUG initiator codon for the fr lysis (L) gene. However, 4 codons further downstream there is a UUG codon which proved to be the start codon for the fr lysis gene. This UUG start codon proved crucial for L-gene regulation. It is suggested that terminated but not released ribosomes mediate the L-gene activation. A general eubacterial scanning model is proposed. It seems that ribosomes can scan the mRNA in both directions and reinitiate at the first encountered restart site. This eubacterial scanning model parallels the eukaryotic translation initiation mechanism

The ecophysiology of bacteriophage infecting halophilic archaebacteria

An ecophysiological study of halophages, isolated from the Yallahs Salt Ponds, Jamaica, has been performed to determine (i) what effect, if any, the single most important environmental parameter, salinity, has on phage-bacterium interactions, and (ii) which phage functions and phage-bacterium interactions are most likely to be of long term significance to the co-existence of halophage and halobacteria in nature. Results indicate that the NaCl concentration governs the interactions between halophages and the extremely halophilic strains of halobacterium. Phage growth is invariably attentuated at high salinity. A more detailed study on a single phage isolate, S5100, shows that at high salinities the maturation of phage is repressed, and lytic phage infections give way to persistent infections. In most instances, the frequency of productive infections initiated by each phage on each sensitive host strain is a consistent function of the host rather than the phage. Closer inspection revealed that the intracellular stages of the phage infection process have a higher degree of host specificity than the cellular receptor sites. It has been demonstrated that mutations to higher virulence and/or extended host range occur in the morphological group A1 phages. Phage absorption is implicated as the stage of the phage infection process that is affected by these mutations. The group B1 halophage, S45, is restricted and modified in vivo by strains of Halobacteriums. Three strain-specific activities have been observed. Two of these occur in the same bacterial strain and appear to be due to different kinds of enzymatic activities. One of the restriction specificities is shown to be associated with a strain-specific endonuclease active on unmodified halobacterial DNA. These phenomena that have been observed are discussed with respect to possible implications for phage ecology and evolution (AU)