Many gram-positive bacteria have acidic components called teichoic acids embedded in their cell wall. Teichoic acids were discovered in 1958 by Armstrong and co-authors.
The term teichoic acid encompasses a diverse family of cell surface glycopolymers containing phosphodiester-linked polyol repeat units. Teichoic acids are fibers of glycerol phosphate (glycerol teichoic acid) or ribitol phosphate (ribitol teichoic acid).
Teichoic acids are located in the outer layer of certain Gram-positive bacteria (such as Staphylococci, Streptococci, Lactobacilli, and Bacillus spp). So far teichoic acids have not been found in Gram-negative Bacteria.
Types of Teichoic Acids
- Lipoteichoic acids (LTAs): Teichoic acids that are covalently linked to the lipid in the cytoplasmic membrane.
- Wall teichoic acids (WTAs): Teichoic acids that are covalently attached to muramic acid in the wall peptidoglycan.
Wall teichoic acids are intimately involved in many aspects of cell division and are essential for maintaining cell shape in rod-shaped organisms. WTAs are required for ß-lactam resistance in methicillin-resistant S. aureus (MRSA), and they modulate susceptibility to cationic antibiotics in several organisms.
Functions of Teichoic Acids
- Teichoic acids play a role in pathogenesis by promoting adherence to host tissues. For example, S. pyogenes adhere to pharyngeal epithelium via pili composed of lipoteichoic acid and M protein.
- They induce septic shock through the same pathways as does endotoxin (lipopolysaccharide ) in Gram-negative bacteria.
- Lipoteichoic acids play a role in the induction of septic shock by inducing cytokines such as interleukin-1 (IL-1) and tumor necrosis factor (TNF) from macrophages.
- Teichoic acids are highly negatively charged polymers so they can serve as a cation-sequestering mechanism. Teichoic acids bind Ca2+ and Mg2+ for their eventual transport into the cell.