The prevalence of functional quorum‐sensing systems in recently emerged Vibrio cholerae toxigenic strains

Abstract

SummaryVibrio cholerae live in aquatic environments and cause cholera disease. Like many other bacteria, V. cholerae use quorum-sensing (QS) systems to control various cellular functions, such as pathogenesis and biofilm formation. However, some V. cholerae strains are naturally QSdefective, including defective mutations in the quorum sensing master regulator HapR. Here we examined the QS functionality of 602 V. cholerae clinical and environmental strains isolated in China from 1960-2007, by measuring QS-regulated gene expression. We found that a greater percentage of the toxigenic strains (ctxAB + ) had functional QS as compared to the non-toxigenic strains (ctxAB − ), and that this trend increased significantly over time. We hypothesize that QS provides adaptive value in V. cholerae pathogenic settings.

“Quorum Non-Sensing”: Social Cheating and Deception in Vibrio cholerae

“…Surprisingly, however, ca. 50% of natural V. cholerae isolates are QS deficient, most of which bear mutations in the hapR gene, implying a selective advantage of QS Ϫ mutants in nature (17)(18)(19). Similar findings have been noted in the opportunistic pathogen Pseudomonas aeruginosa, where strains containing mutations in LasR, the regulator of QS in P. aeruginosa, have been isolated from a variety of infection origins (20).…”

“…QS regulates a number of important physiological functions in V. cholerae, but previous work has shown that Ͼ50% of V. cholerae natural isolates are QS-deficient mutants, most of which contain mutations in the QS master regulator gene hapR (17)(18)(19), indicating that QS-deficient isolates may have a selective advantage under certain conditions. To test this hypothesis, we mixed wild-type cells with hapR inframe deletion mutants representing QS Ϫ strains and propagated this mixture under various growth conditions.…”

“…S3 in the supplemental material), suggesting that the absence of QS mutants in the presence of glucose is not due to catabolite repression. Sequencing of the hapR coding region of 37 in vitro QS-deficient mutants isolated from separate populations grown on casein protein indicated that a majority of these mutants (35 of 37) had defects in the HapR protein, some of which contained identical mutations seen in clinical and environmental isolates previously reported (17,18) (Fig. 2B, red symbols).…”

“…Because clinical and environmental QS-deficient strains display a variety of mutations within the hapR reading frame (17)(18)(19), we reasoned that natural QS Ϫ isolates are likely due to separate spontaneous mutational events and subsequent selection rather than migration of mutants into new populations. To test whether hapR mutants could emerge de novo within a population, we propagated 10 populations of wild-type V. cholerae separately under conditions utilizing either protein or glucose as a carbon source and sampled the dynamics of QS deficiency mutants within the population over 25 days of growth (ϳ170 generations).…”

Bacterial Quorum Sensing Stabilizes Cooperation by Optimizing Growth Strategies

“…2 and 3). These results have ecological significance, as nonluminescent luxR defectors and UC luxO mutants have all been identified in natural Vibrio populations (43)(44)(45). Importantly, this occurred in a well-mixed environment in which no biofilms or cell aggregates were observed and neither assortment of competitors nor privatization of PG would be likely.…”