Inhibition of quorum sensing in Chromobacterium violaceum by Syzygium cumini L.and Pimenta dioica L.

Objective:To investigated into the anti-quorum sensing(QS)activity of Syzygium cumini L.(S.cumini)and Pimenta dioica L.(P.dioica)using Chromobacterium violaceum(C.violaceum)strains.Methods:In this study,anti-QS activity of ethanol extract of Syzygium cumini L.and Pimenta dioica L.were screened using C.violaceum CV026 biosensor bioassay.By bioassay guided fractionation of 5.cumini and P.dioica,ethyl acetate fraction(EAF)with strong anti-QS activity was separated.Inhibition of QS regulated violacein production in C.violaceum ATCC12472 by EAF was assessed at different concentrations.The effect of EAF on the synthesis of autoinducer like N-acyl homoserine lactone(AHL)was studied in C.violaceum ATCC31532 using its mutant C.violaceum CV026 by standard methods.Results:EAF inhibited violacein production in C.violaceum ATCC12472 in a concentration dependent manner without significant reduction in bacterial growth.Complete inhibition of violacein production was evidenced in 0.75-1.0 mg/mL concentration of EAF without inhibiting the synthesis of the AHL.TLC biosensor overlay profile of EAF revealed two translucent spots in 5.cumini and P.dioica that inhibited C_6-AHL mediated violacein production in C.violaceum CV026.Conclusions:This study indicates the anti-QS activity of the tested medicinal plants against C.violaceum.