Biofilm Formation by Pathogenic Bacteria: The Role of Quorum Sensing and Physical - Chemical Interactions

Abstract

Pathogenic bacteria cause infectious diseases, mainly when the host (humans, animals, and plants) are colonised by bacteria, especially in its biofilm stage, where it is known to cause chronic infections. Biofilms are associated with resistance to antimicrobial agents, including antibiotics, antiseptics, detergents, and other therapeutic approaches. Antimicrobial resistance (AMR) is one of the biggest public health challenges of our time and is termed a ‘silent pandemic’ by the United Nations. Biofilm formation, pathogenicity and the associated AMR are regulated through a bacterial cell-to-cell communication system termed “Quorum Sensing (QS)’. As the bacterial cells sense the fluctuations in their population, they biosynthesise and secrete the signalling molecules called autoinducers (AI). In gram-negative, the signalling molecules are primarily homoserine lactones (AHL) whereas in gram-positive the signalling molecules are autoinducing peptides. The AI binds to receptor and regulator proteins in the bacterial cells to activate the complete QS system, which controls the regulations of various genes that are essential for the biosynthesis of virulence factors, extracellular biopolymers (EPS) production, biofilm formation and bacterial fitness.