Gram-positive bacterial peptidoglycan (PGN)

Gram-positive bacterial peptidoglycan, also known as murein, is an essential and unique macromolecule that forms a thick, mesh-like layer (sacculus) surrounding the cytoplasmic membrane of Gram-positive bacteria (Wikipedia, 2024). It consists of alternating residues of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) cross-linked by short peptide chains, providing the structural integrity necessary to withstand high internal osmotic pressure (PMC, 2020). Because peptidoglycan is absent in eukaryotic cells, it serves as a primary and highly selective target for numerous antibiotic classes (Frontiers, 2023). Drugs such as glycopeptides (e.g., vancomycin) exert their bactericidal effect by binding to the D-alanyl-D-alanine terminus of peptidoglycan precursors, thereby inhibiting the assembly of the cell wall (PubMed, 2021). Beyond its structural role, peptidoglycan fragments act as pathogen-associated molecular patterns (PAMPs) that are recognized by host innate immune receptors like NOD2, initiating inflammatory signaling during infection (NIH, 2022). The thickness and composition of the peptidoglycan layer are key determinants of bacterial survival and are frequently modified by pathogens to evade host immune responses and develop antibiotic resistance (Nature Communications, 2023). In Gram-positive species, this layer is significantly thicker than in Gram-negative bacteria, often comprising up to 90% of the cell wall's dry weight (Wikipedia, 2024). This structural prominence makes it a critical factor in the pathogenesis of infections caused by organisms such as Staphylococcus aureus and Streptococcus pneumoniae (StatPearls, 2023).

Other names

MureinMucopeptideBacterial cell wall sacculusPeptidoglycan layer

Inhibition of cell wall synthesis by binding to the D-Ala-D-Ala terminus of peptidoglycan precursors (glycopeptides), sequestration of lipid II and other precursors (clovibactin, teixobactin), or enzymatic hydrolysis of the glycan backbone (lysozyme).