The peptidoglycan sacculus is the stress-bearing structure of bacterial cells. It consists of glycan strands cross-linked by peptide bridges. Peptidoglycan, or murein as it is also known, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria. The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine and N-acetylmuramic acid residues. Attached to the N-acetylmuramic acid is a peptide chain of three to five amino acids. The peptide chain can be cross-linked to the peptide chain of another strand forming the three-dimensional mesh-like layer.

The peptidoglycan layer is much thicker in Gram-positive bacteria than in Gram-negative bacteria.

Peptidoglycan biosynthesis is the target for many antibiotics such as β-lactams, D-cycloserine and glycopeptide-antibiotics such as vancomycin. Bacteria have developed a number of different antibiotic resistance mechanisms for coping with these antibiotics.


Further reading:
Bacterial Polysaccharides
Biopolymers and Polymer Precursors

Labels: biopolymers, Gram-positive bacteria, peptidoglycan, polysaccharides