Role of the Histone-Like Nucleoid Structuring Protein in the Regulation of rpoS and RpoS-Dependent Genes in Vibrio cholerae

被引:34
|
作者
Silva, Anisia J. [1 ]
Sultan, Syed Zafar [1 ]
Liang, Weili [2 ]
Benitez, Jorge A. [1 ]
机构
[1] Morehouse Sch Med, Dept Microbiol Biochem & Immunol, Atlanta, GA 30310 USA
[2] Chinese Ctr Dis Control & Prevent, Natl Inst Communicable Dis Control & Prevent, State Key Lab Infect Dis Prevent & Control, Beijing 102206, Peoples R China
关键词
D O I
10.1128/JB.00360-08
中图分类号
Q93 [微生物学];
学科分类号
071005 ; 100705 ;
摘要
Production of the Zn-metalloprotease hemagglutinin (HA)/protease by Vibrio cholerae has been reported to enhance enterotoxicity in rabbit ileal loops and the reactogenicity of live cholera vaccine candidates. Expression of HA/protease requires the alternate sigma factor sigma(S) (RpoS), encoded by rpoS. The histone-like nucleoid structuring protein (H-NS) has been shown to repress rpoS expression in Escherichia coli. In V. cholerae strains of the classical biotype, H-NS has been reported to silence virulence gene expression. In this study we examined the role of H-NS in the expression of HA/protease and motility in an El Tor biotype strain by constructing a Delta hns mutant. The Delta hns mutant exhibited multiple phenotypes, such as production of cholera toxin in non-permissive LB medium, reduced resistance to high osmolarity, enhanced resistance to low pH and hydrogen peroxide, and reduced motility. Depletion of H-NS by overexpression of a dominant-negative allele or by deletion of hns resulted in diminished expression of HA/protease. Epistasis analysis of HA/protease expression in Delta hns, Delta rpoS, and Delta hns Delta rpoS mutants, analysis of RpoS reporter fusions, quantitative reverse transcription-PCR measurements, and ectopic expression of RpoS in Delta rpoS and Delta rpoS Delta hns mutants showed that H-NS posttranscriptionally enhances RpoS expression. The Delta hns mutant exhibited a lower degree of motility and lower levels of expression of flaA, flaC, cheR-2, and motX mRNAs than the wild type. Comparison of the mRNA abundances of these genes in wild-type, Delta hns, Delta rpoS, and Delta hns Delta rpoS strains revealed that deletion of rpoS had a more severe negative effect on their expression. Interestingly, deletion of hns in the rpoS background resulted in higher expression levels of flaA, flaC, and motX, suggesting that H-NS represses the expression of these genes in the absence of sigma(S). Finally, we show that the cyclic AMP receptor protein and H-NS act along the same pathway to positively affect RpoS expression.
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页码:7335 / 7345
页数:11
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