Chapter 8 - The Pneumococcal Cell Wall

Abstract

Streptococcus pneumoniae has a highly complex cell wall made of a mesh-like peptidoglycan (PG) with covalently linked wall teichoic acid (WTA) and capsular polysaccharides. The glycan chains in PG are modified by deacetylation of N-acetylglucosamine residues and O-acetylation of N-acetylmuramic acid residues. Unlike many other species, pneumococci have the same, unusually complex repeating unit structure in WTA and lipoteichoic acid, which has recently been revised. Depending on the strain, the teichoic acids have a mean length of 7–8 repeats and contain 1–2 phosphorylcholine residues per repeat. The cell wall is synthesized at a central growth zone, presumably by large multiprotein complexes which alternate between peripheral and septal modes of synthesis, resulting in the characteristic oval cell shape. Cell wall components released from the bacterial cell during growth and cell lysis are recognized by components of the host, contributing to the multitude of interactions between this pathogen and the human organism.