Carvacrol Inhibits Quorum Sensing in Opportunistic Bacterium Aeromonas hydrophila

Bacterial quorum sensing (QS) plays a crucial role in chemical communication between bacteria involving autoinducers and receptors and controls the production of virulence factors in bacteria. Therefore, reducing the concentration of signaling molecules in QS is an effective strategy for mitigating the virulence of pathogenic bacteria. In this study, we demonstrated that carvacrol at 15.625 μg/mL (1/4 MIC), a natural compound found in plants, exhibits potent inhibitory activity against QS inChromobacterium violaceum, as evidenced by a significant reduction (62.46%) in violacein production. Based on its impressive performance, carvacrol was employed as a natural QS inhibitor to suppress the pathogenicity ofAeromonas hydrophilaNJ-35. This study revealed a significant reduction (36.01%) in the concentration of N-acyl-homoserine lactones (AHLs), a QS signal molecular secreted byA. hydrophilaNJ-35, after 1/4 MIC carvacrol treatment. Moreover, carvacrol was found to down-regulate the expression ofahyR/I, two key genes in the QS system, which further inhibited the QS system ofA. hydrophilaNJ-35. Finally, based on the above results and molecular docking, we proposed that carvacrol alleviate the pathogenicity ofA. hydrophilaNJ-35 through QS inhibition. These results suggest that carvacrol could serve as a potential strategy for reducing the virulence of pathogenic bacteria and minimizing the reliance on antibiotics in aquaculture.Keywords:A. hydrophila;carvacrol;N-acyl-homoserine lactones;pathogenicity;quorum sensing