Complete genome sequence of Pseudomonas aeruginosa PAO1, an opportunistic pathogen

Pseudomonas aeruginosa is a ubiquitous environmental bacterium that is one of the top three causes of opportunistic human infections. A major factor i n its prominence as a pathogen is its intrinsic resistance to antibiotics a nd disinfectants. Here we report the complete sequence of P. aeruginosa str ain PAO1. At 6.3 million base pairs, this is the largest bacterial genome s equenced, and the sequence provides insights into the basis of the versatil ity and intrinsic drug resistance of P. aeruginosa. Consistent with its lar ger genome size and environmental adaptability, P. aeruginosa contains the highest proportion of regulatory genes observed for a bacterial genome and a large number of genes involved in the catabolism, transport and efflux of organic compounds as well as four potential chemotaxis systems. We propose that the size and complexity of the P. aeruginosa genome reflect an evolut ionary adaptation permitting it to thrive in diverse environments and resis t the effects of a variety of antimicrobial substances.