The Vibrio cholerae Hybrid Sensor Kinase VieS Contributes to Motility and Biofilm Regulation by Altering the Cyclic Diguanylate Level

Abstract

Phosphorelay systems are important mediators of signal transduction during bacterial adaptation to new environments. Previously we described the vieSAB operon, encoding a putative three-protein component phosphorelay involved in regulating Vibrio cholerae virulence gene expression. At least part of the regulatory activity of VieSAB is exerted through the cyclic diguanylate (c-di-GMP)-degrading activity of the putative response regulator VieA. So far no direct evidence that VieSAB encodes a phosphorelay system exists. In addition, the role VieS plays in modulating VieA activity remains unclear. To address these questions, we expressed and purified VieA and a soluble cytoplasmic portion of VieS and used them in autophosphorylation and phosphotransfer assays. These assays showed that VieS has kinase activity in vitro and is able to selectively phosphorylate VieA. A phenotypic comparison revealed that deletion of vieS results in increased biofilm production comparable to that seen for deletion of vieA, whereas motility was decreased only slightly in the ⌬vieS mutant compared to the profound defect observed in a ⌬vieA mutant. We also found that the ⌬vieS strain has a lower level of vieA transcript and, similar to a ⌬vieA mutant, an increased intracellular level of c-di-GMP. Further analysis using site-directed vieA mutants showed that some of the phenotypes observed were due to the phosphorylation status of VieA. The evidence presented in this report is the first to link VieS and VieA biochemically and genetically, lending support to the hypothesis that these proteins function together in a signaling system.

Quorum-regulated biofilms enhance the development of conditionally viable, environmental Vibrio cholerae

“…Studies by Merrell et al (10) provided evidence that passage through the human host alters critical phenotypic properties that enhance the infectivity of V. cholerae in experimental animals. One of these is the down-regulation of motility/chemotaxis, which interestingly has been linked to the up-regulation of EPS production and thus biofilm formation (2,11,24). Our studies indicate that the host-induced changes in V. cholerae also include induction of in vivo biofilm communities that are especially efficient at CVEC formation and are therefore capable of long-term survival when introduced into aquatic environments.…”

Distinct Sensory Pathways in Vibrio cholerae El Tor and Classical Biotypes Modulate Cyclic Dimeric GMP Levels To Control Biofilm Formation

“…By contrast, V. cholerae Cl strain O395, which is naturally HapR Ϫ , does not produce strong biofilms. In this V. cholerae Cl strain, deletion of the gene encoding the EAL protein VieA results in elevated vps expression and biofilm formation (50) The phosphodiesterase VieA is a component of the VieSAB signaling system that controls c-di-GMP levels and hence vps expression and biofilm formation in V. cholerae Cl (32,48,50). While VieA controls Ͼ100 genes in V. cholerae Cl , the role of VieA in V. cholerae El appears to be minor (1).…”

“…By contrast, V. cholerae Cl strain O395, which is naturally HapR Ϫ , uses the phosphodiesterase VieA, a component of the VieSAB system, to control c-di-GMP (Fig. 1B) (32,48,50). Recently, however, we showed that this V. cholerae Cl strain responds to CAI-1 and AI-2 to control the levels of a GGDEF protein through a HapR-independent pathway (15).…”

Two DHH Subfamily 1 Proteins in Streptococcus pneumoniae Possess Cyclic Di-AMP Phosphodiesterase Activity and Affect Bacterial Growth and Virulence

“…In Pseudomonas aeruginosa, the mutation of either c-di-GMP phosphodiesterase gene, pvrR or rocR, also attenuated the virulence in a mouse infection model (7). In addition, c-di-GMP regulates bacterial pathogenesis through the control of motility or biofilm formation in P. aeruginosa, Yersinia pestis, V. cholerae, and S. Typhimurium (5,10,(16)(17)(18)(19).…”

“…Another c-di-GMP phosphodiesterase that contains an HD-GYP domain breaks down c-di-GMP directly into two GMPs (4). c-di-GMP plays a role in the pathogenesis of many bacteria (5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Vibrio cholerae vieA encodes a c-di-GMP phosphodiesterase, and deletion of this gene led to attenuation in an infant mouse model of cholera (13,14).…”