INULA RACEMOSA INHIBITS QUORUM SENSING IN CHROMOBACTERIUM VIOLACEUM AND PSEUDOMONAS AERUGINOSA PAO1H.S. VASAVI, A.B. ARUN AND P.D. REKHAAbstract Plants used in traditional medicines are a promising source of bioactive compounds and some can potentially inhibit bacterial quorum sensing (QS), a cell-cell signaling mechanism mediated by auto inducers to regulate a range of biological functions including virulence in bacteria. Inhibition of QS offers an alternative strategy for antibiotic mediated bactericidal/ bacteristatic approach and believed to reduce the risk for development of resistance. The primary objective of this study was to investigate the anti-QS activity of Inula racemosa Hook f., a member of the family asteraceae. Anti-QS activity of the ethanol extract of I. racemosa was determined by biosensor bioassay using Chromobacterium violaceum CV026. Effect of ethanol extract of I. racemosa on inhibition of QS-regulated violacein production in C. violaceum ATCC12472 and swarming motility in Pseudomonas aeruginosa PAO1 was also determined. The ethanol extract of I. racemosa showed anti-QS activity in biosensor bioassay as indicated by clear turbid halo zone of violacein inhibition in C. violaceum CV026 culture plates. It also showed inhibition of violacein production by more than 80% in C. violaceum ATCC12472 at 1 mg/mL concentration and complete inhibition of swarming motility in P. aeruginosa PAO1 at 0.1 mg/mL concentration. Meanwhile, the growth of C. violaceum and P. aeruginosa PAO1 was not affected significantly at all the tested concentration of I. racemosa ethanol extract. The ability of plants to produce substances that affect QS regulation provides with important tool to manipulate gene expression and control bacterial infections in humans.
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