The bacterial cell wall is a protective structure critical for maintaining cell shape, protecting against osmotic pressure, and providing structural support. It is primarily composed of peptidoglycan, which includes glycan and peptido portions, differing between gram-positive (thick layer) and gram-negative (thin layer with outer membrane). Gram staining distinguishes these bacteria based on their cell wall characteristics, leading to different color expressions that aid in diagnostics.

3. • - Definition: The bacterial cell wall is a protective structure
surrounding bacterial cells.
• - Importance: Provides structural support, protects against osmotic
pressure, and determines cell shape.
• - Composition: Bacterial cell walls are composedof peptidoglycan, a
complexpolysaccharide.

4. • - Glycan portion : A complex polysaccharide , is
composed of two types of regularly alternating
sugar molecules , called N-
acetylglucosamine(NAG) and N-acetylmuramic
acid(NAM). Millions of NAG and NAM molecules
are covalently linked in a chain. This chains
are the “glycan” portions of peptidoglycan.
• - Peptido portion : Chains of NAG and NAM are
attached to other chains by crossbridge of four
amino acids (tetrapeptides) . These peptide
crossbridge are the “peptido” portion of
peptidoglycan.

5. • - Thick peptidoglycan layer : Gram positive
bacteria have a thick layer of peptidoglycan.
• - Teichoic Acids: Unique polymers of glycerol
and ribitol phosphate , embedded in the cell
wall , which provide rigidity . Some teichoic
acids are covalently linked to lipid , forming
lipoteichoic acids that anchor the
peptidoglycan to the cytoplasmic membrane
• - Staining: Gram positive bacteria express blue
to purple color due to the thick peptidoglycan
layer.

6. - Single layer : Theyhave onlyone cell membrane.
- Role of pathogenicity: Theycan cause disease.

7. • - Thinpeptidoglycan layer : gram negative bacteria have a thin
peptidoglycanlayer surroundedby an outer membrane.
• -Outermembrane : Theypossess an outermembrane containing
lipopolysaccharides(LPS) , whichcan be an endotoxin. LPSis a
union of lipid withsugar . The lipidportion of LPSis known as
Lipid A.

8. • - Periplasmic Space: The space between the
innerand outermembranescontaining
enzymes and other proteins.
• -PORINS: Their outer membrane have porins .
• -Resistance to Antibiotics : The outer
membrane act as a barrier to certain
antibiotics.
• -Staining: Gram negative bacteria expresses
red or orange colordue to thin peptidoglycan
layer.

10. The cell wall differ gram
positive and gram negative
bacteria . Gram staining is an
important diagnostic tool . After
the gram staining procedure ,
gram negative bacteria appear
pink and gram positive bacteria
appear purple .

11. functions
• -It provides overall strength to the cell.
• -It helps maintain the cells shape ,
which is essential for growth ,
reproduction , and movement.
• -Protect bacteria from osmotic forces.
Etc

12. THANK YOU
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