title: A branch in the ToxR regulatory cascade of Vibrio cholerae revealed by characterization of toxT mutant strains.
abstract: Co-ordinate expression of genes associated with pathogenicity in Vibrio cholerae requires two transcription activators, ToxR and ToxT. Work carried out to date suggests that ToxR activates transcription of the toxT gene and that ToxT directly activates transcription of several genes whose products play a role in colonization or CT production by V. cholerae. Previous work also suggests that ToxR can directly activate transcription of the CT operon (ctxAB) independently of ToxT, thereby implying a degree of complexity in control of the cixAB operon not found with other genes of the ToxR regulon. We tested the regulatory cascade model of virulence gene expression by constructing strains of classical and El Tor V. cholerae deleted for the coding sequence for the putative DNA-binding domain of toxT. Phenotypic analysis of these strains suggests that V. cholerae has ToxT-dependent and ToxT-independent branches of its virulence regulon. The results also raise questions about the precise role for ToxR in activation of ctxAB transcription.
authors.affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48108-0620, USA.
authors.forename: G A
authors.initials: GA
authors.lastname: Champion
authors.forename: M N
authors.initials: MN
authors.lastname: Neely
authors.forename: M A
authors.initials: MA
authors.lastname: Brennan
authors.forename: V J
authors.initials: VJ
authors.lastname: DiRita
mesh_terms: D018829:Adhesins, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics*; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D016133:Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D014734:Vibrio cholerae / Q000235:genetics* / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics
chemical_list: D018829:Adhesins, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; C096349:OmpU protein, Vibrio cholerae; D014157:Transcription Factors; C499324:toxR protein, Vibrio cholerae; C066719:toxR protein, bacteria; C075626:tcpN protein, Vibrio cholerae