ThevprAB-ompV-virKoperon ofVibrio choleraesenses antimicrobial peptides and activates the expression of multiple resistance systems

Abstract

AbstractAntimicrobial peptides are small cationic molecules produced by eukaryotic cells to combat infection, as well as by bacteria for niche competition. Polymyxin B (PmB), a cationic cyclic antimicrobial peptide, is used prophylactically in livestock for infection prevention and as a last-resort treatment for multidrug-resistant bacterial infections in humans. In this study, a transcriptomic analysis inVibrio choleraeshowed that expression of the uncharacterized geneompVis stimulated in response to PmB. We found thatompVis organized in a conserved four-gene operon with the two-component systemvprAB(carRS) andvirKinV. cholerae, and that these genes are also upregulated in response to PmB treatment. AvirKdeletion mutant was more sensitive to the human cathelicidin LL-37 than the wild-type strain, while anompVmutant was more sensitive to PmB and LL-37, suggesting that both OmpV and VirK contribute to antimicrobial resistance inV. cholerae. This increased sensitivity to antimicrobial peptides was not due to membrane destabilization or reduced sequestration by membrane vesicles as a result ofompVdeletion. Instead, our transcriptomic analysis showed that the efflux pumpvexAB, a known effector of PmB resistance, was also upregulated in the presence of PmB in anompV-dependent manner. Examination of the predicted structure of OmpV revealed a lateral opening in the β-barrel wall with access to an electronegative pocket in the barrel lumen that can accommodate PmB. Such an interaction could facilitate intracellular signaling through a conformational change in OmpV. This is the first evidence of a specialized operon governing multiple systems for antimicrobial resistance inV. cholerae.Author SummaryIn this study, we identified the first specialized operon controlling multiple systems of antimicrobial resistance inV. cholerae. The operon encodes the two-component systemvprAB, which activates the main mechanism of polymyxin B resistance inV. cholerae, and the uncharacterized genesompVandvirK. We provide evidence that OmpV and VirK are implicated in antimicrobial resistance and show that OmpV has a membrane-accessible lateral opening into a pocket that could accommodate the antimicrobial peptide polymyxin B. We propose that OmpV acts as an outer membrane sensor that signals the presence of antimicrobial peptides to activate the expression of the operon, leading to the activation of multiple mechanisms of resistance, including modifications of the outer membrane and the multi-drug efflux systemvexAB.