Peptidoglycan

Definition
noun, plural: peptidoglycans
(1) A glycan (a polysaccharide) attached to short cross-linked oligopeptides in the cell wall of eubacteria
(2) A crystal lattice structure in the bacterial cell wall that is made up of linear chains of alternating amino sugars, namely N-acetylglucosamine and N-acetylmuramic acid, and short peptide chains of three to five amino acids (attached to the N-acetylmuramic acid). The peptide chains form cross-links between them resulting in a 3D mesh-like structure.
(3) A polymer that serves a structural role in the bacterial cell wall, giving structural strength, as well as counteracting the osmotic pressure of the cytoplasm. It is also involved in binary fission during bacterial cell reproduction.
Supplement
The peptidoglycan layer of Gram-positive bacteria is substantially thicker than that of Gram-negative bacteria. Hence, Gram-positive bacteria are more susceptible to certain antimicrobial agents like penicillin and other β-lactam antibiotics that work by inhibiting the formation of peptidoglycan cross-links thereby weakening their cell wall.
Synonym: mucopeptide, murein.

See also: cell wall (bacteria).