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The Vibrio cholerae FlgM Homologue Is an Anti-σ(28) Factor That Is Secreted through the Sheathed Polar Flagellum

By Nidia E. Correa, Jeffrey R. Barker and Karl E. Klose

Abstract

Vibrio cholerae has a single polar sheathed flagellum that propels the cells of this bacterium. Flagellar synthesis, motility, and chemotaxis have all been linked to virulence in this human pathogen. V. cholerae expresses flagellar genes in a hierarchy consisting of σ(54)- and σ(28)-dependent transcription. In other bacteria, σ(28) transcriptional activity is controlled by an anti-σ(28) factor, FlgM. We demonstrate that the V. cholerae FlgM homologue (i) physically interacts with σ(28), (ii) has a repressive effect on some V. cholerae σ(28)-dependent flagellar promoters, and (iii) is secreted through the polar sheathed flagellum, consistent with anti-σ(28) activity. Interestingly, FlgM does not have a uniform repressive effect on all σ(28)-dependent promoters, as determined by measurement of σ(28)-dependent transcription in cells either lacking FlgM (ΔflgM) or incapable of secretion (ΔfliF). Further analysis of a ΔfliF strain revealed that this flagellar assembly block causes a decrease in class III (FlrC- and σ(54)-dependent) and class IV (σ(28)-dependent), but not class II (FlrA- and σ(54)-dependent), flagellar transcription. V. cholerae flgM and fliA (encodes σ(28)) mutants were only modestly affected in their ability to colonize the infant mouse intestine, a measure of virulence. Our results demonstrate that V. cholerae FlgM functions as an anti-σ(28) factor and that the sheathed flagellum is competent for secretion of nonstructural proteins

Topics: Microbial Cell Biology
Publisher: American Society for Microbiology
Year: 2004
DOI identifier: 10.1128/JB.186.14.4613-4619.2004
OAI identifier: oai:pubmedcentral.nih.gov:438600
Provided by: PubMed Central
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