The chaperone/usher pathways of Pseudomonas aeruginosa: Identification of fimbrial gene clusters (cup) and their involvement in biofilm formation

Pseudomonas aeroginosa, an important opportunistic human pathogen, persists in certain tissues in the form of specialized bacterial communities, refer red to as biofilm, The biofilm is formed through series of interactions bet ween cells and adherence to surfaces, resulting in an organized structure, By screening a library of Tn5 insertions in a nonpiliated P. aeruginosa str ain, we identified genes involved in early stages of biofilm formation. One class of mutations identified in this study mapped in a cluster of genes s pecifying the components of a chaperone/usher pathway that is involved in a ssembly of fimbrial subunits in other microorganisms, These genes, not prev iously described in P. aeruginosa, were named cupA1-A5. Additional chaperon e/usher systems (CupB and CupC) have been also identified in the genome of P. aeruginosa PAO1; however, they do not appear to play a role in adhesion under the conditions where the CupA system is expressed and functions in su rface adherence. The identification of these putative adhesins on the cell surface of P, aeruginosa suggests that this organism possess a wide range o f factors that function in biofilm formation. These structures appear to be differentially regulated and may function at distinct stages of biofilm fo rmation, or in specific environments colonized by this organism.