Species-specific quorum sensing represses the chitobiose utilization locus inVibrio cholerae

Abstract

AbstractThe marine facultative pathogenVibrio choleraeforms complex multicellular communities on the chitinous shells of crustacean zooplankton in its aquatic reservoir.V. cholerae-chitin interactions are critical for the growth, evolution, and waterborne transmission of cholera. This is due, in part, to chitin-induced changes in gene expression in this pathogen. Here, we sought to identify factors that influence chitin-induced expression of one locus, the chitobiose utilization operon (chb), which is required for the uptake and catabolism of the chitin disaccharide. Through a series of genetic screens, we identified that the master regulator of quorum sensing, HapR, is a direct repressor of thechboperon. We also found that the levels of HapR inV. choleraeare regulated by the ClpAP protease. Furthermore, we show that the canonical quorum sensing cascade inV. choleraeregulateschbexpression in a HapR-dependent manner. Through this analysis we found that signaling via the species-specific autoinducer CAI-1, but not the inter-species autoinducer AI-2, influenceschbexpression. This phenomenon of species-specific regulation may enhance the fitness of this pathogen in its environmental niche.ImportanceIn nature, bacteria live in multicellular and multispecies communities. Microbial species can sense the density and composition of their community through chemical cues using a process called quorum sensing (QS). The marine pathogenVibrio choleraeis found in communities on the chitinous shells of crustaceans in its aquatic reservoir.V. choleraeinteractions with chitin are critical for the survival, evolution, and waterborne transmission of this pathogen. Here, we show thatV. choleraeuses QS to regulate the expression of one locus required forV. cholerae-chitin interactions.