Fig. 6: Model of how AI-2 and bile stimulate the synthesis of c-di-GMP to repress the T3SS through targeting the CesD/SycD/LcrH family of chaperones.
From: Autoinducer-2 and bile salts induce c-di-GMP synthesis to repress the T3SS via a T3SS chaperone

The QS signal AI-2 and host-derived cues, including bile components taurocholate and taurodeoxycholate induce an increase in intracellular c-di-GMP concentrations via the DGCs YeaJ and YedQ, respectively. When the intracellular c-di-GMP level is elevated, higher amounts of the T3SS chaperone SicA bound by c-di-GMP will result in less binding of SicA to InvF, SipB, and SipC, thus reducing transcription of the T3SS-1 genes such as sopB, sopE2, sicA, sipB, and sipC while impairing the presecretory stabilization and efficient secretion of SipB and SipC. OM outer membrane, IM inner membrane.