RpoS and quorum sensing control expression and polar localization of Vibrio cholerae chemotaxis cluster III proteins in vitro and in vivo

Abstract

Summary The diarrheal pathogen Vibrio cholerae contains 3 gene clusters that encode chemotaxis-related proteins, but only cluster II appears to be required for chemotaxis. Here, we present the first characterization of V. cholerae's “cluster III” chemotaxis system. We found that cluster III proteins assemble into foci at bacterial poles, like those formed by cluster II proteins, but the two systems assemble independently and do not colocalize. Cluster III proteins are expressed in vitro during stationary phase and in conjunction with growth arrest linked to carbon starvation. This expression, as well as expression in vivo in suckling rabbits, is dependent upon RpoS. V. cholerae's CAI-1 quorum sensing (QS) system is also required for cluster III expression in stationary phase and modulates its expression in vivo, but is not required for cluster III expression in response to carbon starvation. Surprisingly, even though the CAI-1 and AI-2 QS systems are thought to feed into the same signaling pathway, the AI-2 system inhibited cluster III gene expression, revealing that the outputs of the two QS systems are not always the same. The distinctions between genetic determinants of cluster III expression in vitro and in vivo highlight the distinctive nature of the in vivo environment.

Baseplate variability of Vibrio cholerae chemoreceptor arrays

“…Vibrio cholerae contains three chemotaxis operons (clusters I to III), each of which forms its own structurally distinct arrays. Of these, clusters I and III are expressed only under certain growth conditions (low oxygen and as a general stress response, respectively) (16)(17)(18). The proteins from cluster I form cytoplasmic arrays, in which two baseplate layers sandwich cytosolic chemoreceptors and are stabilized by a specialized receptor with two signaling domains (19,20).…”

Repurposing a macromolecular machine: Architecture and evolution of the F7 chemosensory system

“…Flagellar motility in these organisms is controlled by the F6 chemosensory system (39)(40)(41), which is expressed under a variety of conditions. In contrast, the P. aeruginosa and V. cholerae F7 system is only expressed when cells are grown in stressful conditions such as into late stationary phase, induced by the stress-related sigma factor RpoS (30,42,43). Expression of the F7 system in different conditions has not been studied in S. oneidensis or M. alcaliphilum, but both organisms live in unique and challenging environments which may be poorly mimicked by laboratory growth; S. oneidensis is a facultative anaerobe adapted to changing environments (44) and M. alcaliphilum is a haloalkaliphilic methanotroph (21).…”

Differential Localization of Chemotactic Signaling Arrays during the Lifecycle of Vibrio parahaemolyticus

“…Preparation of V. parahaemolyticus swimmer cells for fluorescence microscopy was carried out essentially as described (Ringgaard et al, 2015; Briegel et al, 2016). A volume of 10 mL of LB was inoculated with a bacterial colony of V. parahaemolyticus from an over-night LB agar plate grown at 37°C and relevant antibiotic.…”