Escherichia coli

Escherichia coli isolates produce a range of cell-surface polysaccharides which mediate interactions between the bacteria and their environment. The best-studied glycoconjugates are lipopolysaccharide (LPS) and capsular polysaccharide (CPS). LPS is a component of the outer membrane in all E. coli strains and it plays a critical role in the barrier properties of the cell envelope and resistance to host factors including cationic antimicrobial peptides and the complement system. LPS is also a biologically active molecule that activates TLR4-mediated signaling leading to endotoxic shock. In contrast, only some strains of E. coli make capsular polysaccharides (CPSs). The capsule plays a major role in evasion of the host immune system and is particularly important for the pathogenesis of uropathogenic and meningitis-associated E. coli. This chapter discusses the biosynthesis of LPS and capsule as well as their contributions to the virulence of pathogenic E. coli.