Peptidoglycan (pep-tid-o-gly-can) is a molecule found only in the cell walls of bacteria. Its rigid structure gives the bacterial cell shape, surrounds the plasma membrane and provides
Article Summary: Amount and location of the peptidoglycan molecule in the prokaryotic cell wall determines whether a bacterium is Gram-positive or Gram-negative.
You have free access to a large collection of materials used in two college-level introductory microbiology courses (8-week & 16-week). The Virtual Microbiology Classroom provides a wide range of free educational resources including PowerPoint Lectures, Study Guides, Review Questions and Practice Test Questions.
Gram-positive
Staphylococcus. Thick peptidoglycan cell wall retains crystal violet primary Gram stain. Go to >
Peptidoglycan is a huge organic polymer; a mesh-like series interlocking strands of sugars -- N-acetylglucosamine (NAG) and N- acetylmuramic acid (NAM) -- cross-linked by short amino acid bridges.
During Gram staining, these thick, multiple layers (20–80 nm) of peptidoglycan retain the dark purple primary stain crystal violet, whereas Gram-negative bacteria stain pink.