title: Activation of the Vibrio cholerae SOS response is not required for intestinal cholera toxin production or colonization.
abstract: Cholera toxin, one of the main virulence factors of Vibrio cholerae, is encoded in the genome of CTXphi, a V. cholerae-specific lysogenic filamentous bacteriophage. Although the genes encoding cholera toxin, ctxAB, are known to have their own promoter, the toxin genes can also be transcribed from an upstream CTXphi promoter, PrstA. The V. cholerae SOS response to DNA damage induces the CTX prophage by stimulating gene expression initiating from PrstA. Here, we investigated whether ctxA mRNA levels increase along with the levels of the transcripts for the other CTXphi genes following stimulation of the V. cholerae SOS response. Treatment of V. cholerae with the SOS-inducing agent mitomycin C increased the level of ctxA mRNA approximately sevenfold, apparently by augmenting the activity of PrstA. However, using suckling mice as a model host, we found that intraintestinal ctxA transcription does not depend on PrstA. In fact, the suckling mouse intestine does not appear to be a potent inducer of the V. cholerae SOS response. Furthermore, alleviation of LexA-mediated repression of the V. cholerae SOS regulon was not required for V. cholerae growth in the suckling mouse intestine. Our observations suggest that pathogenicity of V. cholerae does not depend on its SOS response.
authors.affiliation: Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Ave., Boston, MA 02111, USA.
authors.forename: Mariam
authors.initials: M
authors.lastname: Quinones
authors.forename: Brigid M
authors.initials: BM
authors.lastname: Davis
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Waldor
mesh_terms: D000818:Animals; D000833:Animals, Suckling; D001435:Bacteriophages / Q000235:genetics / Q000502:physiology; D002771:Cholera / Q000382:microbiology; D002772:Cholera Toxin / Q000096:biosynthesis* / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007421:Intestine, Small / Q000382:microbiology*; D051379:Mice; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D013014:SOS Response, Genetics; D041241:Vibrio cholerae O1 / Q000254:growth & development / Q000472:pathogenicity* / Q000821:virology; D014774:Virulence
chemical_list: D012333:RNA, Messenger; D002772:Cholera Toxin