Factors Affecting the Organization of Group 1 Capsular Polysaccharides on the Surface of Escherichia coli
Many pathogenic isolates of Escherichia coli produce capsular polysaccharide (CPS). CPS make up a network of interacting polysaccharide chains to create a capsule layer covering the cell surface. Capsules protect E. coli from elements of host immune defenses. While some aspects of the E. coli group 1 CPS assembly and export are understood, details of their association with the cell surface and interplay with other surface structures are unresolved. It has been proposed that lipopolysaccharide (another class of surface glycoconjugate) molecules help stabilize the attachment of CPS. To test this, deletions in certain lipopolysaccharide-biosynthesis genes were made in a prototype isolate of E. coli E69 and their effect on capsule formation was examined by Western immunoblotting using CPS-specific antibodies, and sensitivity to a capsule-specific bacteriophage. An ELISA was developed to quantitate CPS production in the wild-type and mutants, leading to better understanding of influence of lipopolysaccharide structure on capsule organization.