THE ROLE OF QUORUM SENSING SIGNALS ON THE INTERACTIONS BETWEEN VIBRIO CHOLERAE AND CHIRONOMIDS MICROBIOTA

Vibrio cholerae causes the fatal cholera diarrhea and is a natural inhabitant of aquatic ecosystems. We commonly isolate V. cholerae along with other bacteria from all four life stages of chironomid insects. V. cholerae secretes Haemagglutinin/Protease (HAP) that degrades the gelatinous matrix of chironomid egg masses, likely acquiring nutrients and consequently preventing egg masses hatching. A few clinical V. cholerae strains have been shown to induce HAP by Quorum Sensing (QS), a cell-cell communication process in which accumulation of secreted signal molecules (autoinducers, AIs) triggers an intracellular regulatory cascade. Our aim was to define the role of QS AI signals in HAP production by V. cholerae, in mixed species consortia on chironomid egg masses. The effect of chironomid microbiota on V. cholerae was studied using V. cholerae bioluminescence reporter strains (QS-proficient V. cholerae O1 El-Tor wild type strain C6706 and QS-deficient V. cholerae mutants). We were able to demonstrate that V. cholerae responds to AIs produced by other members of the chironomid bacterial consortium, by expressing hapA gene. Chironomid endogenous bacterial species have recently been shown to play a role in protecting the insect host from toxicants. These bacteria may use the degraded gelatinous matrix of the egg mass for their own growth. By doing so, these other species may in turn control the population levels of V. cholerae in the egg mass. So too V. cholerae supports the maintenance of endogenous bacteria in the egg mass by secreting HAP. Understanding the interactions between V. cholerae and other endogenous bacteria in the insect host system may help uncover the interactions between this pathogen and the human gut.