Project description:Using a combination of ChIP-seq and RNA-seq we show that ToxT regulates expression of the small RNA TarB. TarB modulates the expression level of the transcriptioanl repressor VC0177. VC0177 controls expression of several genes including VC0179. The function of the Vibrio 7th pandemic island-1 (VSP-1) in cholera pathogenesis has remained obscure. Utilizing ChIP-seq and RNA-seq to map the regulon of the master virulence regulator ToxT, we identify a TCP island encoded small RNA that reduces the expression of a previously unrecognized VSP-1 encoded transcription factor termed VspR. VspR modulates the expression of several VSP-1 genes including one that encodes a novel class of di-nucleotide cyclase (DncV), which preferentially synthesizes a previously undescribed hybrid cyclic AMP-GMP molecule. We show that DncV is required for efficient intestinal colonization and down-regulates V. cholerae chemotaxis, a phenotype previously associated with hyperinfectivity. This pathway couples the actions of previously disparate genomic islands, defines VSP-1 as a pathogenicity island in V. cholerae and implicates its occurrence in 7th pandemic strains as a benefit for host adaptation through the production of a regulatory cyclic di-nucleotide.
