Infection by choleraphage phi 138: bacteriophage DNA and replicative intermediates

Mechanism of phage PS166-mediated biotype conversion in Vibrio cholerae: role of the hlyA locus

Temperate phage PS166 lysogens of Vibrio eltor MAK757 biotype eltor belong to two major categories. Seventy percent of the lysogens acquire auxotrophy for glycine and histidine and maintain their parental biotype. About 10% of the lysogens become Cys(-) or Cys(-) Met(-) and are converted to the classical biotype with complete changes in all biotype-specific determinants. PCR and RFLP analysis revealed that in the latter lysogens, the phage genome integrated at the hlyA locus, whereas the same locus remained unaffected in lysogens that retained their parental biotype. These results suggest that the two types of lysogens arose due to integration of the phage genome at two different locations on the chromosome. A restriction map of the phage genome was constructed using AvaII and BglII. An 800-bp BglII fragment carrying the attP site, located at one of the termini of the phage genome, was used to distinguish the two classes of lysogen.

Biophysical characterization of Vibrio El Tor typing phage e5

Vibrio cholerae typing phage e5, which can lyse only the El Tor strains of V. cholerae, was characterized. The phage had a polyhedral head 51 nm in diameter and a short tail 13 nm in length. It contained 13 structural polypeptides, with the molecular mass of the major component being 50 kDa. Phage chromosome comprised a 38.5-kb linear double-stranded DNA molecule with unique termini, as determined by restriction fragment analysis and electron microscopy, and had a G+C content of 35.5%. A physical map was constructed with the restriction endonucleases HaeII and HpaII. Adsorption of the phage to its host followed a biphasic kinetics and its intracellular growth was characterized by a latent period of 15 min and a burst size of 100 particles per infected cell. The phage was found to be moderately thermotolerant.

A 14-kilodalton inner membrane protein of Vibrio cholerae biotype e1 tor confers resistance to group IV choleraphage infection to classical vibrios

Choleraphage phi 149 differentiates the two biotypes, classical and el tor, of Vibrio cholerae. This phage cannot replicate in V. cholerae biotype el tor cells because the concatemeric DNA intermediates produced are unstable and cannot be chased to mature phage DNA. A V. cholerae biotype el tor gene coding for a 14,000-Da inner membrane protein which destabilizes the concatemeric DNA intermediates by hindering their binding to the cell membrane has been identified. Presumably, a 22,000-Da V. cholerae biotype el tor protein might also have a role in conferring phage phi 149 resistance to cells belonging to the biotype el tor. A nucleotide sequence homologous to the 1.2-kb V. cholerae biotype el tor DNA coding for both the 14,000- and 22,000-Da proteins is present in all strains of classical vibrios but is not transcribed. The nucleotide sequence of the gene coding for the 14,000-Da protein has been determined.

The cloning and expression of transfer RNA gene cluster of Vibrio eltor phage e4

Vibrio eltor phage e4 codes for five different tRNA species (S. Chattopadhyay and R. K. Ghosh, 1988, Virology, 165, 606-608). The tRNA genes contained in a 3.4-kb KpnI fragment (S. Chattopadhyay and R. K. Ghosh, 1988, Virology, 162, 337-345) have been cloned in pUC 19 at the KpnI site. Two recombinant plasmids, pSR216 and pSR112, produced four of the five tRNA species (arginine, isoleucine, tyrosine, and tryptophan) encoded in the phage genome. The tRNA genes were located on a 1.45-kb KpnI-HindIII subfragment.

Lack of umuDC gene functions in Vibrio cholerae cells

Attempts to identify an umuDC analog, using interspecific complementation of Escherichia coli mutants with plasmids containing a gene bank of Vibrio cholerae, were not successful. The DNA from none of the vibrio species examined including marine vibrios hybridized to E. coli umuC and umuD gene sequences. These cells are not mutable by ultraviolet (UV) light and cannot Weigle-reactivate UV-irradiated choleraphages, suggesting that vibrios are deficient in the umuDC operon. This possibility is supported by the fact that when the plasmid pKM101 carrying the mucAB genes is introduced into V. cholerae cells, they acquire the UV-mutable phenotype and UV-irradiated choleraphages can be Weigle-reactivated.

Abortive replication of choleraphage phi 149 in Vibrio cholerae biotype el tor

Choleraphage phi 149 adsorbed irreversibly to Vibrio cholerae biotype el tor cells, and 50% of the injected phage DNA bound to the cell membrane. Although no infectious centers were produced at any time during infection, the host macromolecular syntheses were shut off and the host DNA underwent chloramphenicol-inhibitable degradation. Synthesis of monomeric phage DNA continued similar to that observed in the permissive host. However, the concatemeric DNA intermediates produced were unstable and could not be chased to mature phage DNA. Pulse-labeling of UV-irradiated infected cells at different times during infection allowed identification of phage-specific proteins made in this nonpermissive host. Although most of the early proteins were made, only some of the late proteins were transiently synthesized.

Characterization of phage-specific transfer RNA molecules coded by Vibrio eltor phage e4

Transfer RNAs were isolated from phage e4-infected Vibrio eltor Mak 757 cells. These were aminoacylated with 14 individual 3H-labeled L-amino acids. Hybridization of these [3H]aminoacyl-tRNAs with phage e4 DNA revealed that the phage e4 encodes tRNAs for arginine, tryptophan, tyrosine, leucine, and isoleucine. Direct aminoacylation of phage-coded tRNA molecules isolated from phage DNA-RNA hybrids also confirmed this observation.

Analysis in vivo of the bacteriophage P22 headful nuclease

Bacteriophage P22 packages its double-stranded DNA chromosomes from concatemeric replicating DNA in a processive, sequential fashion. According to this model, during the initial packaging event in such a series the packaging apparatus recognizes a nucleotide sequence, called pac, on the DNA, and then condenses DNA within the coat protein shell unidirectionally (rightward) from that point. DNA ends are generated near the pac site before or during the condensation reaction. The right end of the mature chromosome is created by a cut made in the DNA by the "headful nuclease" after a complete chromosome is condensed within the phage head. Subsequent packaging events on that concatemeric DNA begin at the end generated by the headful cut of the previous event and proceed in the same direction as the previous event. We report here accurate measurements of the P22 chromosome length (43,400( +/- 750) base-pairs, where the uncertainty is the range in observed lengths), genome length (41,830( +/- 315) base-pairs, where the uncertainty represents the accuracy with which the length is known), the terminal redundancy (1600( +/- 750) base-pairs or 3.8( +/- 1.8)%, where the uncertainty is the observed range) and the imprecision in the headful measuring device ( +/- 750 base-pairs or +/- 1.7%). In addition, we present evidence for a weak nucleotide sequence specificity in the headful nuclease. These findings lend further support to, and extend our understanding of, the sequential series model of P22 DNA packaging.

Localization of transfer RNA genes on the physical map of Vibrio eltor phage e4 genome

Transfer RNAs were isolated from uninfected and phage e4-infected Vibrio eltor Mak 757 cells. These tRNAs were then aminoacylated with 3H-labeled amino acids and hybridized to DNA isolated from phage e4. Significant hybridization was observed only with tRNA isolated from phage e4-infected cells. Restriction enzyme digestion of phage e4 DNA followed by Southern blot using [32P]tRNA from infected cells revealed that tRNA genes were contained in a 3.4-kb Kpnl fragment. The tRNA genes were located on the physical map of the phage genome 19 kb from one of the termini.

Replication and packaging of choleraphage phi 149 DNA

The intercellular replication of the circularly permuted DNA of choleraphage phi 149 involves a concatemeric DNA structure with a size equivalent to six genome lengths. The synthesis of both monomeric and concatemeric DNAs during replication of phi 149 occurred in the cytoplasm. The concatemers served as the substrate for the synthesis of mature phage DNA, which was eventually packaged by a headful mechanism starting from a unique pac site in the concatemeric DNA. Packaging of DNA into phage heads involved binding of concatemeric DNA to the cell membrane. A scheme involving sequential packaging of five headfuls proceeding in the counterclockwise direction from the pac site is proposed. After infection under high-phosphate conditions, the concatemeric DNA intermediates were not formed, although synthesis of monomeric molecules was unaffected.

Genetics of Vibrio cholerae and its bacteriophages

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Cloning and expression in Escherichia coli of a recA-like gene from Vibrio cholerae

A library containing more than 80% of the Vibrio cholerae genome was constructed by cloning BamH1 restriction fragments into pBR322. Using interspecific complementation of an Escherichia coli recA mutant with plasmids containing the gene bank of V. cholerae, a recA-like gene was identified. The recombinant plasmid, designated as pDP145, contained a 1.45 kb segment of V. cholerae DNA which codes for a protein of molecular weight 39,000. The product of this gene confers methyl methane sulphonate resistance on the E. coli recA mutant, suppresses its ultraviolet (UV) light sensitive phenotype and has proteolytic activity on the phage lambda repressor. Induction of a 39,000 dalton protein in UV-irradiated V. cholerae cells was demonstrated.