Question

How does peptidoglycan affect gram staining?

Answer 1

Hint: By painting these cells red or violet, the Gram stain technique differentiates between Gram-positive and Gram-negative types. Due to the presence of a thick layer of peptidoglycan in their cell walls, Gram-positive bacteria stain violet, which retains the crystal violet that these cells are stained with.

Complete answer:
A common technique used to separate two large groups of bacteria based on their different constituents of the cell wall is gram staining.
By painting these cells red or violet, the Gram stain technique differentiates between Gram-positive and Gram-negative types. Owing to the presence of a thick layer of peptidoglycan in their cell walls, Gram-positive bacteria stain violet, which preserves the crystal violet these cells are stained with.
Alternatively, Gram-negative bacteria stain red, which is due to a thinner wall of peptidoglycan which during the decolorizing phase does not maintain the crystal violet.
Even if the laboratory technician feels she knows what the results will be, all steps are performed. Gram staining requires three processes: staining with a crystal violet water-soluble dye, decolorization, and counterstaining, typically with safranin (light red).
Gram-positive bacteria (with a thicker peptidoglycan layer) maintain crystal violet stain throughout the decolorization process due to variations in the thickness of the peptidoglycan layer in the cell membrane between Gram-positive and Gram-negative bacteria, whereas Gram-negative bacteria lose the crystal violet stain and are stained in the final staining process by safranin instead.

Note:
Osmotic lysis is prevented by peptidoglycan. Bacteria concentrate the dissolved nutrients (solute) by active transport, as seen earlier under the cytoplasmic membrane. As a consequence, the cytoplasm of the bacterium is normally hypertonic to its surrounding environment, and through the bacterium is the net flow of free water. The bacterium will burst from the osmotic pressure of the water without a solid cell wall.