ASSESSMENT OF QUORUM QUENCHING ACTIVITY OF SERRATIA SPP. ISOLATED FROM PLANT RHIZOSPHERE AGAINST QUORUM SENSING CONTROLLED BIOFILM-FORMING PATHOGENS

Quorum quenching is the process of blocking quorum sensing activity that can be used as an effective way to control quorum sensing dependent virulence in pathogens. Quorum quenching mechanisms prevent the development of antibiotic resistance in biofilm-forming microorganisms. Rhizospheric bacteria shows great diversity along with complex intra species interactions. Within this diversified environment many bacterial species with quorum sensing and quorum quenching ability are found in close vicinity. In this study rhizospheric soil of different plants was used to screen potential quorum quenchers. The rhizospheric bacterial isolates were tested for their ability to degrade/inactivate N-hexanoyl-l-homoserine lactone (C6HSL) molecules. Pigment inhibition bioassays were performed using Chromobacterium violaceum CV026 and C. violaceum 2656 to screen bacterial isolates possessing quorum quenching activity. The biofilm formation inhibition by six screened isolates was studied against different human pathogens such as Vibrio parahaemolyticus MTCC451, V. cholerae MTCC3906 and Pseudomonas aeruginosa PA01. Results revealed that biofilms were efficiently inhibited. Significant biofilm inhibition was revealed by two isolates and identified as S. marcescens subsp. sakuensis KRED, and S. nematodiphila using 16S rRNA gene sequencing technique. The partial purification of C6HSL inactivating quorum quenching molecule resulted in maximum pigment inhibition of C. violaceum 2656 at 80% saturation of ammonium sulphate. These findings revealed that S. marcescens subsp. sakuensis KRED and S. nematodiphila are found to be potential candidates to control biofilms in bacterial human pathogens.