FIGURE 8.

Schematic diagram of the mode of action of TRQ-mediated virulence inhibition in P. aeruginosa. Without introduction, the QS systems and their upstream regulators work smoothly (A). In our study (B), we have found that TRQ could efficiently inhibit the transcription of upstream regulators of QS systems in P. aeruginosa. Particularly, we found that two TCSs, GacS/GacA and PprA/PprB, were involved in these process. One of the sigma factors, RpoS, was also identified to positively affect the expression of PprA/PprB system (Wang et al., 2019). The expression of c-AMP synthesis was also inhibited by TRQ treatment, suggesting that the downstream Vfr-mediated QS activation via lasR was shutdown. In addition, TCS GacS/GacA was found to be involved in the regulation of QS signal synthesis by LasI and RhlI (Reimmann et al., 1997). With the introduction of TRQ, all those processes might be affected and thus the virulent phenotypes diminished (avirulence). AI, autoinducer; P, phosphorylated.