Phosphate repression of phage protein synthesis during infection by choleraphage phi 149

Heat shock response and heat shock protein antigens of Vibrio cholerae

Sixteen heat shock proteins (Hsps) have been identified in the hypertoxinogenic strain 569B of Vibrio cholerae which are synthesized in response to small and large elevations of temperature. The induction of the Hsps is necessary for the cells to survive the deleterious effects of heat. There is no difference in the pattern of induction of the Hsps in V. cholerae strains varying in levels of toxinogenicity. One of the major low-molecular-mass Hsps, a 16-kDa protein, is preferentially degraded following shift down of temperature. This protein is induced at a much lower level at high temperatures in cells maintained in the laboratory for a prolonged period. The only Hsp located in the outer membrane of V. cholerae cells is a 23-kDa protein. Western immunoblot analysis with human immune sera collected from convalescent cholera patients revealed that this protein is markedly immunogenic. The human immune serum also reacted with the 69- and 16-kDa major Hsps and the 88-, 66-, and 46-kDa Hsps but not with the 61-kDa major Hsp identified as the groEL gene product. All major Hsps reacted with rabbit anti-V. cholerae sera. Ethanol stress leads to the induction of four of the major Hsps and three additional proteins.

Cell surface characteristics of environmental and clinical isolates of Vibrio cholerae non-O1

The cell surfaces of several toxigenic and nontoxigenic environmental and clinical isolates of Vibrio cholerae non-O1 have been examined. The environmental strains, irrespective of toxigenicity, are significantly more resistant to antibiotics and detergents than are V. cholerae O1 strains. The clinical isolates of non-O1 vibrios are as sensitive to a wide variety of chemicals as the O1 vibrios. The environmental non-O1 strains are also less susceptible to lysis when treated with protein denaturants or neutral and anionic detergents than are O1 vibrios and the clinical non-O1 strains. In contrast to O1 vibrios, the environmental non-O1 vibrios do not have exposed phospholipids in their outer membranes. These features of the cell surfaces of environmental non-O1 vibrios might have a role in the better survival of these organisms under environmental fluctuations.

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.

Cloning and characterization of mutL and mutS genes of Vibrio cholerae: nucleotide sequence of the mutL gene

The mutL and mutS genes of Vibrio cholerae have been identified using interspecific complementation of Escherichia coli mutL and mutS mutants with plasmids containing the gene bank of V. cholerae. The recombinant plasmid pJT470, containing a 4.7 kb fragment of V. cholerae DNA codes for a protein of molecular weight 92,000. The product of this gene reduces the spontaneous mutation frequency of the E. coli mutS mutant. The plasmid, designated pJT250, containing a 2.5 kb DNA fragment of V. cholerae and coding for a protein of molecular weight 62,000, complements the mutL gene function of E. coli mutL mutants. These gene products are involved in the repair of mismatches in DNA. The complete nucleotide sequence of mutL gene of V. cholerae has been determined.

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.

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.

Infection by choleraphage phi 138: bacteriophage DNA and replicative intermediates

Choleraphage phi 138 contains a linear, double-stranded, circularly permuted DNA molecule of 30 X 10(6) daltons or 45 kilobase pairs. Upon infection, the host DNA is degraded, and synthesis of phage-specific DNA is detectable 20 min after infection. The phage utilizes primarily the host DNA degradation products for its own DNA synthesis. A physical map of phi 138 DNA was constructed with the restriction endonucleases Bg/II, HindIII, and PstI. A concatemeric replicative DNA intermediate equivalent to eight mature genome lengths was identified. The concatemer was shown to be the precursor for the synthesis of mature bacteriophage DNA which is subsequently packaged by a headful mechanism.

Characterization and physical map of choleraphage phi 149 DNA

Choleraphage phi 149 DNA is a linear double-stranded molecule 69 X 10(6) Da or 104 kilobase pairs (kbp). From restriction enzyme analysis, it has been concluded that the DNA is circularly permuted. There are at least three S1 nuclease-sensitive sites along the length of the molecule. These sites represent single-strand interruptions repairable by T4 DNA ligase. A physical map of the DNA has been constructed using the restriction endonucleases BamH1 and BglII.