SUMMARY
Pseudomonas aeruginosa is an infectious rod like bacterium which is equipped with a unique quorum-sensing system to sense the surrounding environment and communicate with bacterial cells in vicinity through excreting small molecules, called autoinducers. Quorum sensing system and autoinducer production are cellular density dependent mechanisms which are responsible for cell-cell signalling and regulating biological processes in this bacterium. P. aeruginosa is equipped with an arsenal of virulence factors and tools to protect it from toxins and host immune response which facilitate its survival in a wide range of habitats and environments. The most important virulence factor is biofilm which comprises of sessile community of bacteria covered with a matrix of polysaccharides and extracellular proteins offering enhanced resistance to antibiotics and host immune system. P. aeruginosa produces biofilms at a variety of infection sites in patients, on medical instruments and medical tools inside the patient body. It is very hard to eradicate and inhibit the formation of biofilms in immunocompromised patients. In this article, we described the stages of biofilm formation along with the role of various genetic and biochemical factors required for its formation. Special emphasis was given to extra-cellular appendages (flagella, pili and fimbriae) for their role in attachment of P. aeruginosa to the semi-solid serfaces and converting motile bacteria to sessile mode of life (biofilm). Moreover, polysaccharide matix formation and its resistance towards antibiotics is discussed. This review article can help in devising gene therapy strategies against biofilm formation and its eradication in nosocomial infections caused by drug resistant bacteria.