Pseudomonas Aeruginosa - Cell-surface Polysaccharides

Cell-surface Polysaccharides

Cell-surface polysaccharides play diverse roles in the bacterial "lifestyle". They serve as a barrier between the cell wall and the environment, mediate host-pathogen interactions, and form structural components of biofilms. These polysaccharides are synthesized from nucleotide-activated precursors, and, in most cases, all the enzymes necessary for biosynthesis, assembly, and transport of the completed polymer are encoded by genes organized in dedicated clusters within the genome of the organism. Lipopolysaccharide is one of the most important cell-surface polysaccharides, as it plays a key structural role in outer membrane integrity, as well as being an important mediator of host-pathogen interactions. The genetics for the biosynthesis of the so-called A-band (homopolymeric) and B-band (heteropolymeric) O antigens have been clearly defined, and much progress has been made toward understanding the biochemical pathways of their biosynthesis. The exopolysaccharide alginate is a linear copolymer of β-1,4-linked D-mannuronic acid and L-glucuronic acid residues, and is responsible for the mucoid phenotype of late-stage cystic fibrosis disease. The pel and psl loci are two recently discovered gene clusters, which also encode exopolysaccharides found to be important for biofilm formation. A rhamnolipid is a biosurfactant whose production is tightly regulated at the transcriptional level, but the precise role it plays in disease is not well understood at present. Protein glycosylation, in particular of pilin and flagellin, is a recent focus of research by several groups, and it has been shown to be important for adhesion and invasion during bacterial infection.