Twin Peaks: Presenting the Antagonistic Molecular Interplay of Curcumin with LasR and LuxR Quorum Sensing Pathways

Quorum sensing in bacteria is a cell density-dependent phenomenon in which, a community of cells communicate with each other using signalling molecules belonging to various families of which N-acyl homoserine lactone (AHL) is one. AHL acts via ligand-receptor interaction where receptors of AHL differ from species to species, and possess great degree of similarity in conformation at the active site. A macromolecule, LasR, is a receptor protein that binds to N-(3-oxododecanoyl)-L-homoserinelactone (OdDHL), a type of AHL, viz. responsible for biofilm formation in Pseudomonas aeruginosa. Similar macromolecule LuxR, like LasR, found in Vibrio sp. identifies a different AHL, N-(3-oxohexanoyl)-L-homoserine lactone (OhHSL), responsible for the phenomenon of bioluminescence. In silico study depicted that curcumin could bind to both LasR and LuxR by unique sets of hydrogen bonding and hydrophobic interactions that can lead to the inactivation of these proteins, enabling this plant-derived organic AHL antagonist to be categorized as a quorum sensing inhibitor (QSI). To prove this hypothesis, curcumin was treated on P. aeruginosa to access the reduction in biofilm formation and on V. alginolyticus to check its efficacy to reduction in bioluminescence by inhibition of QS. The results of these studies proved curcumin to be an efficient QSI.