Biology subjects

Pauze-Foixet, J.

Publications and source records attributed to Pauze-Foixet, J..

2 recordsLinked to original sources

bioRxiv2024

The vprAB-ompV-virK operon of Vibrio cholerae senses antimicrobial peptides and activates the expression of multiple resistance systems

Antimicrobial 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 in Vibrio cholerae showed that expression of the uncharacterized gene ompV is stimulated in response to PmB. We found that ompV is organized in a conserved four-gene operon with the two-component system vprAB (carRS) and virK in V. cholerae, and that these genes are also upregulated in response to PmB treatment. A virK deletion mutant was more sensitive to the human cathelicidin LL-37 than the wild-type strain, while an ompV mutant was more sensitive to PmB and LL-37, suggesting that both OmpV and VirK contribute to antimicrobial resistance in V. cholerae. This increased sensitivity to antimicrobial peptides was not due to membrane destabilization or reduced sequestration by membrane vesicles as a result of ompV deletion. Instead, our transcriptomic analysis showed that the efflux pump vexAB, a known effector of PmB resistance, was also upregulated in the presence of PmB in an ompV-dependent manner. Examination of the predicted structure of OmpV revealed a lateral opening in the {beta}-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 in V. cholerae. Author SummaryIn this study, we identified the first specialized operon controlling multiple systems of antimicrobial resistance in V. cholerae. The operon encodes the two-component system vprAB, which activates the main mechanism of polymyxin B resistance in V. cholerae, and the uncharacterized genes ompV and virK. 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 system vexAB.

microbiology↗

bioRxiv2023

Elevated concentrations of polymyxin B elicit a biofilm-specific resistance mechanism in Vibrio cholerae

Vibrio cholerae can form biofilms both in the aquatic environment and in the human intestine, facilitating the release of hyper-infectious aggregates. Due to the increasing antibiotic resistance that impedes treatment of infections, alternatives need to be found. One of these alternatives is antimicrobial peptides, including polymyxin B (PmB), which is already used to treat infections caused by antibiotic-resistant bacteria. In this study, we first investigated the resistance of V. cholerae O1 El Tor strain A1552 to various antimicrobials under aerobic and anaerobic conditions. An increased resistance to PmB is observed in anaerobiosis, with a 3-fold increase in the dose required for 50% growth inhibition. We then studied the impact of the PmB on the formation and the degradation of V. cholerae biofilms to PmB. Our results show that PmB affects more efficiently biofilm formation under anaerobic conditions. On the other hand, preformed biofilms are susceptible to degradation by PmB at concentrations close to the minimum inhibitory concentration (MIC), resulting in approximately 50% reduction of the biomass. At higher concentrations, we observed less degradation and an opacification of the biofilm structures within 20 minutes post-treatment, suggesting a densification of the structure. This densification does not seem to result from the overexpression of matrix genes but rather from the release of DNA through cellular lysis, forming a protective shield that limits the penetration of the PmB into the biofilm. ImportanceVibrio cholerae is an intestinal pathogen capable of forming biofilms and resisting antimicrobials both in the aquatic environment and during infection. Understanding and determining the resistance of V. cholerae to antimicrobials during the infection is crucial to improve patient care. During the infection and in the aquatic environment, V. cholerae form biofilms, structures that are known for their significance in antimicrobial resistance. In this study, we investigated the antimicrobial resistance of V. cholerae in both aerobic and anaerobic conditions, in their planktonic and biofilm forms. The major finding of this study is the identification of a resistance mechanism specific to elevated concentrations of polymyxin B, a last-resort antimicrobial used in the treatment of infections caused by multidrug-resistant Gram-negative bacteria. This resistance mechanism likely involves the lysis of bacterial cells on the surface of the biofilm, resulting in the release of DNA that provides a protective shield against PmB for bacteria within the biofilm matrix.

microbiology↗