Abstract
Bacterial quorum sensing (QS) is a density dependent communication system that regulates the expression of certain genes including production of virulence factors in many pathogens. Bioactive plant extract/compounds inhibiting QS regulated gene expression may be a potential candidate as antipathogenic drug. In this study anti-QS activity of peppermint (
Mentha piperita
) oil was first tested using the
Chromobacterium violaceum
CVO26 biosensor. Further, the findings of the present investigation revealed that peppermint oil (PMO) at sub-Minimum Inhibitory Concentrations (sub-MICs) strongly interfered with acyl homoserine lactone (AHL) regulated virulence factors and biofilm formation in
Pseudomonas aeruginosa
and
Aeromonas hydrophila
. The result of molecular docking analysis attributed the QS inhibitory activity exhibited by PMO to menthol. Assessment of ability of menthol to interfere with QS systems of various Gram-negative pathogens comprising diverse AHL molecules revealed that it reduced the AHL dependent production of violacein, virulence factors, and biofilm formation indicating broad-spectrum anti-QS activity. Using two
Escherichia coli
biosensors, MG4/pKDT17 and pEAL08-2, we also confirmed that menthol inhibited both the
las
and
pqs
QS systems. Further, findings of the
in vivo
studies with menthol on nematode model
Caenorhabditis elegans
showed significantly enhanced survival of the nematode. Our data identified menthol as a novel broad spectrum QS inhibitor.