Bonding Structure of Peptidoglycan

Bacterial Cell Wall Structure 
Location & Amount of Peptidoglycan in 
Gram-positive vs. Gram-negative Bacteria


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 
prokaryotes with protection from the environment.

Article Summary: Amount and location of the peptidoglycan molecule in the prokaryotic cell wall determines whether a bacterium is Gram-positive or Gram-negative.
Bacterial Cell Wall Structure: Gram + & Gram -
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Prokaryotic Cell, Mariana Ruiz
Gram Positive Stained Staphylococcus Bacteria @ 1000xTM
Staphylococcus. Thick peptidoglycan cell wall retains crystal violet primary Gram stain. Go to > 
More Gram Stain Photos
Gram positive cell wall structure
Page last updated 3/2016

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.
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Continued ... 
Gram-negative Bacteria
Go to PAGE 2 >
Bonding Structure of Peptidoglycan
Gram-positive Cells
In Gram-positive bacteria, peptidoglycan makes up as much as 90% of the thick cell wall enclosing the plasma membrane.

See Page 2 for a diagram of the Gram-negative cell wall and a video on 
Gram Staining!

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Gram Stain
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. 
Illustration of Gram-positive and Gram-negative cell wall.