Structure, Biosynthesis, and Function of Teichoic Acids and Related Cell Wall Glycopolymers in the Gram-positive Cell Envelope

Abstract

The incorporation of characteristic carbohydrate-based polymers into the cell wall is a general trait of most Gram-positive bacteria. These cell wall glycopolymers (CWGs) are attached to the membrane or the peptidoglycan and enclose, for example, the teichoic acids, which belong to the most prevalent types of CWG. The structure, function, and biosynthesis of CWGs are only superficially understood. CWG composition and structure is highly variable and often strain- and species-specific. Recent studies have yielded a more precise picture of the biosynthetic pathway for the wall teichoic acid (WTA) polymers, which are covalently anchored in the cell wall, and the lipoteichoic acid (LTA) polymers, which are attached to the cell membrane of Bacillus subtilis and Staphylococcus aureus. Some Gram-positive bacteria have other CWGs, aside from WTA and LTA, such as polyanionic teichuronic acids or uncharged lipoglycans. CWGs are important in bacterial physiology and various potential functions such as the control of autolytic enzymes, regulation of divalent cations, attachment of surface proteins, or protection against antibacterial molecules have been described. For those bacteria that colonize or infect the host organism, certain CWGs have been implicated in the adherence to host cells and the activation of the immune responses, for example through Toll-like receptors (TLRs). Additionally, CWGs are important targets for vaccines, antimicrobials and diagnostics. Thus CWGs represent an important field for scientific research.