Teichoic acids (cf. Greek τειχος, teichos, "wall") are polymers of glycerol or ribitol linked via phosphodiester bonds. These acids can be found in the cell wall of gram-positive bacteria, such as Staphylococci, Streptococci, Bacillus, Clostridium, Corynebacterium and Listeria, and appear to extend to the surface of the peptidoglycan layer. Teichoic acids are not found in the gram-negative bacteria. They can be either covalently bonded to N-acetylmuramic acid of the peptidoglycan layer, linked to the plasma membrane lipids found in the cytoplasmic membrane, or linked to a terminal D-alanine in the tetrapeptide cross-links between molecules of N-acetylmuramic acid. The combined units comprised of teichoic acids and lipids are referred to as lipoteichoic acids.
Teichoic acids are negatively charged and therefore contribute to the negative charge of the gram-positive cell wall. They may also provide structural support for the cell wall and act as antigen. Teichoic acids also assist in regulation of cell growth by limiting the ability of autolysins to break the β(1-4) bond between the N-acetyl glucosamine and the N-acetylmuramic acid.
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