Molecular determinants and functions of bacterial polysaccharide cellular localization

About This Grant

Project Summary Prior research from our groups and others has shown that Psl and Pel exopolysaccharides (EPS) play important roles within Pseudomonas aeruginosa (Pa) biofilms. These include initiating and maintaining cell-to-cell interactions, maintaining the structure of the biofilm via interactions with extracellular proteins and DNA (eDNA), conferring tolerance of antibiotics and antimicrobial peptides, enabling colonization of lung epithelia, and persistence against the host immune response. While Psl and Pel are known to exist in two distinct forms: a cell- associated and a cell-released form, the role(s) each variant of the polymer may play within biofilms has typically not been considered separately. Distinct roles for cell-associated and cell-released Psl/Pel suggest that these two forms of the polymers are likely chemically or structurally different. Little is known about how these polymers are retained on the cell surface and whether chemical modifications such as deacetylation of Pel may impact this association. In this proposal, we will test the hypothesis that Psl and Pel exist in several different isoforms of variable length and/or chemical modification. The first specific aim will examine these EPS for modifications. The Sia system positively influences the amount of cell-associated Psl and Pel in a c-di-GMP dependent manner but the mechanism by which it does so is unknown. Experiments in this proposal will explore how the Sia system controls Pel/Psl localization to the cell surface. Finally, we hypothesize that the cellular distribution of Psl/Pel controlled by the Sia system will impact adhesion and biofilm biomechanics, interaction of polymers with matrix proteins and eDNA, the susceptibility of Pa to antimicrobial and host defenses as well as pathogenesis. Thus, we will dissect the biological consequences of EPS localization and the contribution(s) each form of the polymer plays within the biofilm.