What is peptidoglycan?
1 Answer
Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of all bacteria (except Mycoplasma) (but not Archaea), forming the cell wall.
A common misconception is that peptidoglycan gives the cell its shape; however, peptidoglycan helps maintain the structural strength of the cell.
The peptidoglycan layer is substantially thicker in Gram-positive bacteria (20 to 80 nanometers) than in Gram-negative bacteria (7 to 8 nanometers). Peptidoglycan forms around 90% of the dry weight of Gram-positive bacteria but only 10% of Gram-negative strains.
Thus, presence of high levels of peptidoglycan is the primary determinant of the characterization of bacteria as gram-positive.
In Gram-positive strains, it is important in attachment roles and identifying purposes. For both Gram-positive and Gram-negative bacteria, particles of approximately 2 nm can pass through the peptidoglycan wall.
Some antibacterial drugs such as penicillin interfere with the production of peptidoglycan by binding to bacterial enzymes known as penicillin-binding proteins or transpeptidases and can prevent the bacteria from dividing.
