Assessment of Quorum Quenching Activity of Bacillus Species Against Pseudomonas aeruginosa MTCC 2297

Abstract

Bacteria communicate among themselves using N-Acyl Homoserine Lactone (AHL) and oligopeptide as signaling or quorum sensing molecules. AHL lactonase, a potent tool for biocontrol, can hydrolyze quorum sensing signal molecule into inactive products and there by blocking the quorum sensing systems. This process is known as quorum quenching. Pseudomonas, Salmonella, E. coli, Vibrio, the gram-negative bacteria, are highly pathogenic and lead to various dreadful diseases by their signaling molecule. Among the organisms, P. aeruginosa, is multi-drug tolerant, by its virulence factor secretions (protease, chitinase, pyocyanin, elastase, rhamnolipid). Keeping this in view, it is planned to determine the quorum quenching effect, the AHL lactonase activity, of Bacillus species such as B. subtilis, B. cereus and B. licheniformis using Chromobacterium violaceum MTCC 2656 as bio reporter model. The Crude Cell Extract (CCE) of the three Bacillus species was used to assess the quorum quenching effect against the supernatant of P. aeruginosa. Our screening result had shown that B. licheniformis has significant quorum quenching activity. Further, HPLC analysis of P. aeruginosa CCE had shown a significant reduction in AHL, which could be due to its breakdown by B. licheniformis AHL lactonase activity. From the SDS-Polyacrylamide gel electrophorestic pattern of B. licheniformis extract the MW of the quorum-quenching molecule was found to be 25 kDa.