Monitoring surfactant mediated defence of gastrointestinal Proteus mirabilis DMTMMK1 against pathogenic consortia of Vibrio cholerae

Abstract

In recent times gastrointestinal infections caused by bacterial pathogens have become potentially life-threatening. Particularly, biofilm assembly participates in stimulating the ailments. Bacterial biofilms hold a pivotal role in disease dispersion, pathogenesis and consortia formation. This study reports the antimicrobial and anti-biofilm efficacy of the native gut bacterium Proteus mirabilis DMTMMK1 effected by the production of biosurfactant. Biosurfactant-producing isolates were screened by preliminary assays, and a surfactant with high emulsification capacity produced by Proteus mirabilis DMTMMK1 was purified and subjected to FTIR and NMR spectral analysis which gave evidence of the active characteristics of the surfactant. In the presence of such bioactive compounds an exponential reduction in secreted protease, haemolysis, quorum sensing, and phenotypic inhibition of swarming motility in pathogenic Vibrio cholerae was observed. Further, SEM and HCS (high-content screening) analysis revealed the hampered and disrupted nature of biofilm and cytometry results emphasized a sizeable dead cell population in Vibrio cholerae that had been treated with biosurfactant. Cytotoxicity assay on Vero cell lines evaluated the LD₅₀ value (600 μg mL⁻¹), which showed significant reduction in cell viability and proliferation upon exposure up to 48 h. Furthermore, challenge survival studies provided evidence of biosurfactant effectively inhibiting intestinal colonization of Vibrio cholerae in the nematode Caenorhabditis elegans.