Cell wall of Gram negative bacteria
Cell wall of Gram negative bacteria is more rigid and thick then Gram postive bacteria.
It is made up of two layers
2. Outer cell wall layer
- It is present in between outer wall layer and cell membrane.
- The structure is similar as gram positive cell wall.
- There are some minor differences in the Gram positive and Gram negative peptidoglycan structure.
- The differences are as follows:-
- The third amino acid of tetrapeptide side chainin Gram positive cell wall is L-lysin which is replaced by Mesodiaminopimilic acid in Gram negative cell wall.
- All N-acetymuramic acid molecules are not linked to tetrapeptide side chain.
- Cross bridges are not made up of glycin molecule they are made up of peptide bond.
Structure of peptidoglcan of Gram negative cell
- So due to all these above factors and mainly because of peptide bond cross linkage the network is lose.
- These lose network in peptidoglycan fails to give rigidity to the cell wall.
- In Gram negative cell wall rigidity of a cell is due to outer wall layer.
2.Outer wall layer
- Outer wall layer is present outer side of peptidoglycan layer.
- Outer wall layer is similar to cell membrane.
- It is made up of four components.
- Phospholipids are present in outer side of outer wall layer.
- It has a polar hydrophilic head and hydrophilic tail.
- It is a bilipid layer.
- It is also present in outer side of outer wall layer.
- It is made up of lipid A, R-core, and “O” side chain.
- Lipid A molecule is made up of lipid so it is hydrophobic in nature.
- R core and “O” side chain is made up of sugar so it is hydrophobic in nature.
- These protiens are structural protiens embeded in phospholipid bilayer.
- Lipoproteins are present in inner side of outer cell wall near peptidoglycan.