Peptidoglükaanists

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 repeating disaccharide unit composed of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), which are cross-linked by short peptide chains. The exact composition of these peptide chains varies among bacterial species.

The synthesis of peptidoglycan is a complex process that occurs in multiple stages, beginning in the cytoplasm and culminating at the cell membrane. Enzymes called transglycosylases are responsible for linking the sugar units, while transpeptidases catalyze the formation of peptide cross-links between adjacent glycan chains. These cross-links are essential for the rigidity and integrity of the cell wall.

Peptidoglycan is a target for many antibiotics, most notably penicillin and its derivatives. These antibiotics inhibit the activity of transpeptidases, preventing the formation of functional peptide cross-links. This leads to a weakened cell wall and ultimately cell lysis, particularly in growing bacteria. The presence and structure of peptidoglycan are also key features used in the Gram staining technique, which differentiates bacteria into Gram-positive and Gram-negative groups based on the thickness and composition of their cell walls. Gram-positive bacteria have a thick layer of peptidoglycan, while Gram-negative bacteria have a thinner layer located within the periplasmic space, external to the plasma membrane and internal to an outer membrane.