peptidoglykaniin

Peptidoglycan is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria. It is a crucial component of the bacterial cell wall, providing structural support and maintaining cell shape. The structure of peptidoglycan is a long chain of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) residues. These sugar chains are cross-linked by short peptide chains attached to the NAM residues. The exact amino acid composition of these peptides can vary between bacterial species.

The presence and structure of peptidoglycan are fundamental to distinguishing between Gram-positive and Gram-negative bacteria. In Gram-positive bacteria, the peptidoglycan layer is thick and located outside the plasma membrane, and it retains the crystal violet stain during the Gram staining procedure. In contrast, Gram-negative bacteria have a much thinner peptidoglycan layer situated between the inner plasma membrane and an outer membrane. This thin layer does not retain the crystal violet stain, appearing pink or red after the counterstain.

The synthesis and maintenance of peptidoglycan are essential for bacterial survival, and enzymes involved in these processes are often targets for antibiotics. For example, penicillin and other beta-lactam antibiotics inhibit the transpeptidases responsible for forming the peptide cross-links, weakening the cell wall and leading to cell lysis. Due to its unique presence in bacteria and its vital role in cell wall integrity, peptidoglycan is a significant target in antimicrobial drug development.