title: RS1 satellite phage promotes diversity of toxigenic Vibrio cholerae by driving CTX prophage loss and elimination of lysogenic immunity.
abstract: In El Tor biotype strains of toxigenic Vibrio cholerae, the CTXϕ prophage often resides adjacent to a chromosomally integrated satellite phage genome, RS1, which produces RS1ϕ particles by using CTX prophage-encoded morphogenesis proteins. RS1 encodes RstC, an antirepressor against the CTXϕ repressor RstR, which cooperates with the host-encoded LexA protein to maintain CTXϕ lysogeny. We found that superinfection of toxigenic El Tor strains with RS1ϕ, followed by inoculation of the transductants into the adult rabbit intestine, caused elimination of the resident CTX prophage-producing nontoxigenic derivatives at a high frequency. Further studies using recA deletion mutants and a cloned rstC gene showed that the excision event was recA dependent and that introduction of additional copies of the cloned rstC gene instead of infection with RS1ϕ was sufficient to enhance CTXϕ elimination. Our data suggest that once it is excised from the chromosome, the elimination of CTX prophage from host cells is driven by the inability to reestablish CTXϕ lysogeny while RstC is overexpressed. However, with eventual loss of the additional copies of rstC, the nontoxigenic derivatives can act as precursors of new toxigenic strains by acquiring the CTX prophage either through reinfection with CTXϕ or by chitin-induced transformation. These results provide new insights into the role of RS1ϕ in V. cholerae evolution and the emergence of highly pathogenic clones, such as the variant strains associated with recent devastating epidemics of cholera in Asia, sub-Saharan Africa, and Haiti.
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: M
authors.initials: M
authors.lastname: Kamruzzaman
authors.affiliation: Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: William Paul
authors.initials: WP
authors.lastname: Robins
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: S M Nayeemul
authors.initials: SM
authors.lastname: Bari
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Shamsun
authors.initials: S
authors.lastname: Nahar
authors.affiliation: Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: Mekalanos
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh faruque@icddrb.org.
authors.forename: Shah M
authors.initials: SM
authors.lastname: Faruque
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000276:immunology; D001435:Bacteriophages / Q000276:immunology*; D002771:Cholera / Q000235:genetics / Q000382:microbiology; D002772:Cholera Toxin / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D007422:Intestines / Q000276:immunology / Q000382:microbiology; D008242:Lysogeny / Q000276:immunology*; D039002:Prophages / Q000276:immunology*; D011817:Rabbits; D012697:Serine Endopeptidases / Q000276:immunology; D014734:Vibrio cholerae / Q000276:immunology*; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D002772:Cholera Toxin; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein