Microarchitecture of Pseudomonas aeruginosa biofilms: A biological perspective

Pseudomonas aeruginosa is an important opportunistic pathogen causing a variety of acute infections including nosocomial pneumonias, sepsis, urinary tract infections, keratitis, wound and skin infections. P. aeruginosa continues to be a leading cause of infections in immunocompromised host including patients with cystic fibrosis and is among the most virulent of the opportunistic pathogens as listed by the Centers of Disease Control (CDC). P. aeruginosa has also developed mechanisms to colonize surfaces by coordinately expressing genes in a density dependent manner regulated by the production of small diffusible molecules called auto inducers or quorum sensing (QS) molecules. Activation of the QS cascade promotes formation of biofilms which provide an encapsulated communal structure that coats mucosal surfaces and invasive devices. These biofilms make conditions more favorable for bacterial persistence as embedded bacteria are inherently more difficult to eradicate by both antibiotic regimens as well as by innate immune systems as compared with those in the planktonic state. The objective of this report is to provide an overview; (i) propagation of P. aeruginosa biofilms; (ii) components of the biofilm matrix and their transcriptional regulation; (iii) key signaling pathways regulating C-di-GMP dependent biofilm dispersal; (iv) characterization of experimental models of biofilms.