VpsR, a member of the response regulators of the two-component regulatory systems, is required for expression of vps biosynthesis genes and EPSETr-associated phenotypes in Vibrio cholerae O1 El Tor

The rugose colonial variant of Vibrio cholerae O1 El Tor produces an exopol ysaccharide (EpS(ETr)) that enables the organism to form a biofilm and to r esist oxidative stress and the bactericidal action of chlorine. Transposon mutagenesis of the rugose variant led to the identification of vpsR, which codes for a homologue of the NtrC subclass of response regulators. Targeted disruption of vpsR in the rugose colony genetic background yielded a nonre verting smooth-colony morphotype that produced no detectable EpS(ETr) and d id not form an architecturally mature biofilm. Analysis of two genes, vpsA and vpsL, within the vps cluster of EpS(ETr) biosynthesis genes revealed th at their expression is induced above basal levels in the rugose variant, co mpared to the smooth colonial variant, and requires vpsR. These results sho w that VpsR functions as a positive regulator of vpsA and vpsL and thus act s to positively regulate EpS(ETr) production and biofilm formation.