An important feature of Pseudomonas aeruginosa pathogenesis is the ability to form surface- associated communities called biofilms. Several types of P. aeruginosa infections are characterized by biofilm formation, including the colonization of indwelling medical devices and the chronic infections present in the airways of people suffering from cystic fibrosis (CF). Biofilm bacteria produce one or more extracellular polymeric substances (EPS) that act as a scaffold, holding biofilm cells together and to a surface. For some time, alginate has been considered the major polysaccharide of the P. aeruginosa EPS biofilm matrix. Recently, our studies indicate that alginate is not a significant component of the EPS matrix of nonmucoid strains, which are responsible for most opportunistic biofilm infections and are also the first to colonize CF patients. Instead, there appear to be other EPS components that mediate biofilm formation. Our lab and others discovered that P. aeruginosa has the capacity to encode two alternative polysaccharides, designated Psl and Pel, which play critical roles in cell surface interactions and biofilm formation. The focus of this proposal is the Pel gene cluster. Our overall objective is to determine the role of Pel in biofilm development, structure, resistance to antimicrobial agents, and pathogenesis. A further understanding of this critical biofilm component will lead to strategies aimed at inhibiting biofilm formation, a key aspect of P. aeruginosa pathogenesis. Despite significant advancements in our knowledge of P. aeruginosa biofilm development, there remain gaps in our understanding of the biofilm matrix composition, as well as the genes responsible for producing this matrix. We have discovered a novel EPS locus that is essential for formation of P. aeruginosa biofilms. Since the matrix provides a critical protective role as well as a scaffold for the developing biofilm, agents aimed at disrupting the matrix would have therapeutic value. A thorough analysis of Pel may lead to the development of such agents and improve the quality of life for C patients as well as individuals with other P. aeruginosa infections that involve biofilms. PUBLIC HEALTH RELEVANCE: is proposal is focused on examining the role of the important biofilm exopolysaccharide Pel in Pseudomonas aeruginosa biofilm formation and pathogenesis. The role of Pel in polysaccharide production, biofilm formation and pathogenesis will be explored.