Question

One of the most important features of most prokaryotes is their cell wall. Please explain the structural and functional properties of the cell walls in gram-positive and gram-negative bacteria.?

Answer 1

Structural and functional properties of cell wall of bacteria:

Gram positive bacteria- Cell wall of this bacteria is very thick and it consists of thick peptidoglycan layer which constitutes 95%bf the cell wall. The cell wall can be completely dissolves in lysosomes. The matrix substance in the cell wall of this bacteria may be polysaccharide or teichoic acid. Glycerol teichoic acid is more widespread in gram positive bacteria only. A major component of the cell wall of gram positive bacteria is lipoteichoic acid which provides antigenic function.

STAINING: It is stained by crystal violet and it becomes violet which cannot be discolored after being treated by alcohol because of its thick layer of peptidoglycan which cannot be dissolved by alcohol.

Gram negative bacteria- Cell wall of this bacteria is thin and is consists of thin layer of peptidoglycan. Only 5% of the cell wall is covered with peptidoglycan layes adjacent to cytoplasmic membrane. The chemical structure of the outer membrane is lipopolysaccharide which is responsible for antigenic properties of stain.

STAINING: Stained with crystal violet it becomes purple and after being treated with alcohol it decolorizes because the cell wall dissolves by alcohol. Dissolution of cell wall occurs due to its thin wall and it cannot retain the purple color. It is again countersttained by safranin which gives pink color.