The cell wall is a tough and rigid structure surrounding the bacterium like a shell. It weighs about 20-25% of the dry weight of the cell.

FUNCTIONS:

1.Shape

2. Protection against osmotic damage

3.Rigidity

4.Cell division

5.Possesses target site for antibiotics, lysozymes and bacteriophages. Carries bacterial antigens that are important in virulence and immunity.

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The rigid part of the cell wall is a peptidoglycan which is a mucopeptide (murein) composed of N-acetyl muramic acid and N-acetyl glucosamine molecules alternating in chains, cross-linked by peptide sub-units.

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DIFFERENCES BETWEEN GRAM POSITIVE AND GRAM NEGATIVE CELL WALL

CHARACTER GRAM POSITIVE GRAM NEGATIVE
Thickness 20-80nm 10nm
Periplasmic space Absent Present
Lipids and Glycoproteins Few(0.3%) Many(58%)
Teichoic acid Present Absent
Peptidoglycan