Altered expression of the ToxR-regulated porins OmpU and OmpT diminishes Vibrio cholerae bile resistance, virulence factor expression, and intestinal colonization.
The transmembrane transcriptional activators ToxR and TcpP modulate expression of Vibrio cholerae virulence factors by exerting control over toxT, which encodes the cytoplasmic transcriptional activator of the ctx, tcp, and acf virulence genes. However, ToxR, independently of TcpP and ToxT, activates and represses transcription of the genes encoding two outer-membrane porins, OmpU and OmpT. To determine the role of ToxR-dependent porin regulation in V. cholerae pathogenesis, the ToxR-activated ompU promoter was used to drive ompT transcription in a strain lacking OmpU. Likewise, the ToxR-repressed ompT promoter was used to drive ompU transcription in a strain lacking both ToxR and OmpT. This strategy allowed the generation of a toxR(+) strain that expresses OmpT in place of OmpU, and a toxR(-) strain that expresses OmpU in place of OmpT. Growth rates in the presence of bile salts and other anionic detergents were retarded for the toxR(+) V. cholerae expressing OmpT in place of OmpU, but increased in toxR(-) V. cholerae expressing OmpU in place of OmpT. Additionally, the toxR(+) V. cholerae expressing OmpT in place of OmpU expressed less cholera toxin and toxin-coregulated pilus, and this effect was shown to be caused by reduced toxT transcription in this strain. Finally, the toxR(+) V. cholerae expressing OmpT in place of OmpU was approximately 100-fold reduced in its ability to colonize the infant-mouse intestine. Our results indicate that ToxR-dependent modulation of the outer membrane porins OmpU and OmpT is critical for V. cholerae bile resistance, virulence factor expression, and intestinal colonization.
Provenzano
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Department of Microbiology, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
Klose
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D018829:Adhesins, Bacterial / Q000235:genetics*; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001646:Bile / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D007421:Intestine, Small / Q000382:microbiology*; D007700:Kinetics; D051379:Mice; D018272:Porins / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014734:Vibrio cholerae / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D014774:Virulence
D018829:Adhesins, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C096349:OmpU protein, Vibrio cholerae; D018272:Porins; D014157:Transcription Factors; C405564:ompT protein, bacteria; C499324:toxR protein, Vibrio cholerae; C066719:toxR protein, bacteria; C075626:tcpN protein, Vibrio cholerae