Pseudomonas aeruginosa biofilms and infections : roles of extracellular molecules

Pseudomonas aeruginosa colonization and biofilm formation is responsible for numerous infections, including chronic infections in cystic fibrosis lung, diabetic foot ulcers, burn wounds, urinary tract infections, eye infections, hospital acquired infections, which lead to morbidity and mortality. Biofilm formation is triggered through Quorum sensing (QS) mechanism and via the QS mechanism, P. aeruginosa populations activate various genes that facilitate secretion of extracellular molecules including extracellular DNA, polysaccharides, proteins, pyocyanin, and siderophores. These molecules are associated with P. aeruginosa colonization, biofilm formation, the stability of the biofilm, protection against antimicrobial agents and shear stress, and virulence. For instance, extracellular DNA plays a prominent role in P. aeruginosa biofilm formation, as well as the stability of biofilm and protection of biofilms against antibiotics. Polysaccharides are mainly accountable for virulence in host and also partly allied with biofilm development. P. aeruginosa exogenous proteins are typically acknowledged as a virulence factor. Pyocyanin is a unique redox molecule specifically secreted by P. aeruginosa and it is a potent virulence factor responsible for oxidative stress and cell death in an infected host. P. aeruginosa also secrets an iron-binding molecule, pyoverdine, which plays a prominent role in iron acquisition required for bacterial metabolism and growth. These molecules complement each other in the establishment of P. aeruginosa biofilms and its associated infection in the host.