Peptidoglycan

Peptidoglycan is a mesh-like polymer of alternating sugars cross-linked by short peptides. It gives most bacterial cell walls mechanical strength and shape.

N-acetylglucosamine: A six-carbon amino sugar found in bacterial peptidoglycan and several other biological molecules. It alternates with N-acetylmuramic acid to form peptidoglycan’s sugar backbone.
Peptidoglycan precursor: A soluble or lipid-linked intermediate used to build peptidoglycan, including the disaccharide peptide unit. Wall assembly begins with precursors made in the cytoplasm and transported across the membrane.
Beta-lactam antibiotics: Antibiotics whose beta-lactam ring inhibits bacterial enzymes involved in peptidoglycan cross-linking. They weaken growing walls by blocking penicillin-binding protein transpeptidases.
Gram-positive bacteria: Bacteria whose cell envelope typically contains a thick peptidoglycan layer outside the cytoplasmic membrane. Their thick exposed wall contrasts with the thinner peptidoglycan of Gram-negative bacteria.
N-acetylmuramic acid: A sugar derivative characteristic of bacterial peptidoglycan, bearing a lactyl group that carries a peptide stem. Its attached peptide stems provide the sites for cross-linking neighboring glycan strands.
UDP-N-acetylglucosamine: An activated nucleotide sugar used as a building block in bacterial peptidoglycan biosynthesis. It supplies the N-acetylglucosamine residue in the repeating wall unit.
Vancomycin: A glycopeptide antibiotic that binds peptidoglycan precursors and inhibits bacterial cell-wall synthesis. It blocks access to precursor ends needed for wall construction.
Gram-negative bacteria: Bacteria with a thin peptidoglycan layer between the cytoplasmic membrane and an outer membrane. Their outer membrane changes how peptidoglycan is exposed and how antibiotics reach it.
Glycan strand: A chain of alternating N-acetylglucosamine and N-acetylmuramic acid residues. These long sugar chains form the mesh’s continuous strands.
UDP-N-acetylmuramic acid: An activated sugar nucleotide carrying a peptide stem, used in bacterial peptidoglycan synthesis. Its peptide-bearing sugar is the immediate precursor to a key lipid-linked building block.

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