Regulation of hemagglutinin/protease expression by the VarS/VarA–CsrA/B/C/D system in Vibrio cholerae

Abstract In this study, through the analysis of Vibrio cholerae 2740-80 mutant strains produced by the cholera toxin subunit B gene containing Mariner-based transposon, we found that disruption of the varS gene, a member of the recently reported sensory system VarS/VarA–CsrA/B/C/D, resulted in altered expression of hemagglutinin/protease A. To further investigate the connection between VarS and HapA, we generated an additional varS mutant, V. cholerae 2740-80-VS, and examined the effect of this mutation on expression of HapA and of genes in the VarS/VarA–CsrA/B/C/D system. 2740-80-VS showed decreased expression of varS , csrB/C , hapR , and hapA along with increased biofilm production. Interestingly, expression of the alternative sigma factor σ s , which is important for adaptation to environmental stress, was also decreased in this mutant. These results indicate that the VarS/VarA–CsrA/B/C/D system is involved in the control of HapA expression and biofilm production in V. cholerae 2740-80 through HapR regulation, and also that VarS/VarA controls expression of σ s for HapA regulation.