Question

Bacteria which retain purple colour after staining with gram stain is

• A. Gram +ve
• B. Gram -ve
• C. Trichous
• D. Spirillum

Answer 1

Answer: (A)

Gram +ve

• The gram staining procedure is based on the principle of the ability of microorganisms to retain colour of the stains used during the gram staining process.
• Gram-positive bacteria retain purple colour after staining. They are not decolourized by treatment with alcohol.
• Whereas gram-negative bacteria are decolourized by the alcohol and lose purple colour.
• When again stained with the second stain, they retain pink colour.
• This major difference is due to the difference in the cell wall component of both the bacteria. Gram-negative bacteria contain an additional peptidoglycan layer and a thin layer of the Lipo-polysaccharide layer.

Thus, the correct answer is 'Gram +ve.'