Quorum quenching activity of rhizosphere bacteria against Ralstonia solanacearum

Many Gram-negative bacteria control the expression of virulence factors through quorum sensing (QS) mechanism. Enzymatic degradation of these signalling molecules is an important possible way to interfere with this QS mechanism. Such quorum quenching (QQ) enzymes are widespread in the bacterial world. The Pseudomonas aeruginosa 2apa, Pseudomonas fluorescens, Serratia marcescens and Azospirillum amazonense which are used as biocontrol agent were tested for QQ activity using Chromobacterium violaceum CV026 biosensor strain. Cell-free lysate of P. aeruginosa 2apa exhibited effective N-acyl homoserine lactone (AHL) degrading ability by inhibiting violacein production in biosensor strain. Further when the cell-free lysate was applied to Ralstonia solanacearum, it resulted in inhibition of biofilm formation. The confocal laser scanning microscopic analysis showed decrease in total biomass formation in treated slides. Our study shows the potential of AHL degradation by AHL acylase present in cell-free lysate of P. aeruginosa 2apa and inhibition of biofilm formation in R. solanacearum.