B-251. Regulation of Vibrio cholerae Surface-Dependent Growth by the PTS Phosphotransfer Cascade

L. Houot, P. I. Watnick;
Children's Hosp., Boston, MA.

Vibrio cholerae is a native inhabitant of diverse aquatic environments, where it has been found in biofilms on the surfaces of plants, plankton, and crustaceans. Due to its ability to adhere to the epithelium of the small bowel and elaborate cholera toxin, it is also the causative agent of the diarrheal disease cholera. Monosaccharides such as glucose are universal energy sources and potent inducers of surface colonization for many microbial species, including V. cholerae. In many bacteria, glucose is transported by the phosphoenol-pyruvate phosphotransferase system (PTS), which is comprised of the general components Enzyme I and Histidine protein (HPr) as well as sugar-specific Enzyme II components. These proteins form a phosphotransfer cascade that ultimately transfers a phosphate to the entering monosaccharide. The components of the cascade also regulate nutrient scavenging, chemotaxis, glycogen utilization, catabolite repression, and inducer exclusion. We previously observed that genes encoding the components of the V. cholerae PTS were co-regulated with the vps genes, which are required for synthesis of the biofilm matrix exopolysaccharide. Thus, we investigated the hypothesis that the PTS might play a regulatory role in V. cholerae biofilm formation. We found that the V. cholerae PTS is a selective repressor of growth of biofilm-associated cells. In particular, the phosphorylated form of EI (EI-P) is responsible for this regulation. When HPr is fully phosphorylated, transfer of phosphate from EI to HPr is blocked. In this scenario, we hypothesize that EI transfers its phosphate into another signal transduction cascade that represses vps gene expression and biofilm growth. We are currently conducting a large scale genetic screen to identify members of this alternative signal transduction cascade. A role for the PTS and, in particular, EI-P in repression of biofilm formation has not previously been reported. Thus, this represents a novel regulatory mechanism and function for the PTS. Because the PTS is well-conserved in diverse bacteria, we suggest that the PTS may be a useful target for modulation of biofilm formation.