IAI FigSearch
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Provenzano, D.
Right arrow Articles by Klose, K. E.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Provenzano, D.
Right arrow Articles by Klose, K. E.

Infection and Immunity, March 2000, p. 1491-1497, Vol. 68, No. 3
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

The Virulence Regulatory Protein ToxR Mediates Enhanced Bile Resistance in Vibrio cholerae and Other Pathogenic Vibrio Species

Daniele Provenzano, Darren A. Schuhmacher, Justin L. Barker, and Karl E. Klose*

Department of Microbiology, University of Texas Health Science Center, San Antonio, Texas 78284-7758

Received 1 October 1999/Returned for modification 12 November 1999/Accepted 7 December 1999

The transmembrane regulatory protein ToxR is required for expression of virulence factors in the human diarrheal pathogen Vibrio cholerae, including cholera toxin (CT) and the toxin coregulated pilus (TCP). ToxR is necessary for transcription of the gene encoding a second regulatory protein, ToxT, which is the direct transcriptional activator of CT and TCP genes. However, ToxR, independent of ToxT, directly activates and represses transcription of the outer membrane porins OmpU and OmpT, respectively. The genes encoding TCP and CT (and including ToxT) lie on horizontally acquired genetic elements, while the toxR, ompU, and ompT genes are apparently in the ancestral Vibrio chromosome. The contribution of ToxR-dependent modulation of outer membrane porins to cholera pathogenesis has remained unknown. We demonstrate that ToxR mediates enhanced bile resistance in a ToxT-independent manner. In both classical and El Tor biotypes of V. cholerae, a toxR mutant strain has a reduced minimum bactericidal concentration (MBC) of bile, the bile component deoxycholate (DC), and the anionic detergent sodium dodecyl sulfate (SDS) compared to both wild-type and toxT mutant strains. Classical and El Tor toxR mutant strains also exhibit reduced growth rates at subinhibitory concentrations of DC and SDS. Growth of either V. cholerae biotype in subinhibitory concentrations of bile or DC induces increased ToxR-dependent production of a major 38-kDa outer membrane protein, which was confirmed to be OmpU by Western blot. Measurement of transcription of a ompUp-lacZ fusion in both biotypes reveals stimulation (about two- to threefold) of ToxR-dependent ompU transcription by the presence of bile or DC, suggesting that ToxR may respond to the presence of bile. The toxR mutant strains of three additional human intestinal pathogenic Vibrio species, V. mimicus, V. fluvialis, and V. parahaemolyticus, display lower MBCs of bile, DC, and SDS and have altered outer membrane protein profiles compared to the parental wild-type strains. Our results demonstrate a conserved role for ToxR in the modulation of outer membrane proteins and bile resistance of pathogenic Vibrio species and suggest that these ToxR-dependent outer membrane proteins may mediate enhanced resistance to bile. We speculate that ToxR-mediated bile resistance was an early step in the evolution of V. cholerae as an intestinal pathogen.

* Corresponding author. Mailing address: Department of Microbiology, University of Texas Health Science Center, 7703 Floyd Curl Dr., San Antonio, TX 78284-7758. Phone: (210) 567-3990. Fax: (210) 567-6612. E-mail: klose{at}uthscsa.edu.

Infection and Immunity, March 2000, p. 1491-1497, Vol. 68, No. 3
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
J. Bacteriol. J. Virol. Eukaryot. Cell
Microbiol. Mol. Biol. Rev. Clin. Vaccine Immunol. All ASM Journals

Copyright © 2000 by the American Society for Microbiology. All rights reserved.