FIGURE 2.

Regulation mechanisms of quorum sensing in V. cholerae. The parallel QS system of V. cholerae possesses AI-2/LuxPQ and CAI-1/CqsS systems, as well as an unidentified third circuit that acts through LuxO. cqsA and luxS genes encode proteins producing AI-2 and CAI-1. Thereafter, AI-2 and CAI-1 are detected and captured by LuxRQ complex and CqsS, respectively, leading to the activation of LuxU and LuxO later. Then, with the aid of σ⁵⁴, sRNAs and their chaperones Hfq are transformed into sRNAs–Hfq complex, which inhibits the transcription of HapR mRNAs, thus blocking the forming of HapR, a transcription factor relevant to the expression of some virulence genes.