In-Vitro Analysis of Quorum Sensing and Virulence Gene Expression in Vibrio cholerae O1 under Environmental Stress

Abstract

Background: Vibrio cholerae adapts to environmental fluctuations by modulating its pathogenicity, a process partly governed by quorum sensing (QS). However, the precise molecular response of QS and virulence systems to a combination of environmental stressors remains incompletely characterized.

Objective: To investigate the regulatory role of QS on the expression of key virulence genes (ctxA, tcpA) in V. cholerae O1 El Tor under various in-vitro environmental stress conditions. Methods: In this laboratory study, V. cholerae cultures were exposed to oxidative (2 mM H2O2), osmotic (5% NaCl), temperature, and nutrient-limiting stresses. We performed experiments in triplicate. Bacterial growth (OD₆₀₀), biofilm formation, and the relative expression of QS genes (luxS, luxO, cqsA, hapR) and virulence genes (ctxA, tcpA) were quantified using RT-qPCR. Results: Environmental stresses significantly impaired bacterial growth, with H2O2 and NaCl causing 37.6% and 48.0% reductions, respectively. Nutrient limitation led to a 1.62-fold increase in biofilm formation and upregulated ctxA (1.90-fold) and tcpA (2.10-fold) expression. Conversely, oxidative stress increased hapR expression (2.8-fold) while suppressing ctxA and tcpA. A strong negative correlation was observed between hapR and ctxA expression (r = −0.82, p < 0.001) and between hapR and tcpA (r = −0.76, p = 0.002).

Conclusion: These in-vitro findings suggest that environmental stressors trigger a QS-mediated regulatory switch in V. cholerae, balancing survival mechanisms like biofilm formation against the expression of virulence factors. This highlights the adaptive flexibility.