Question

In Gram staining, cell walls of Gram-positive bacteria become dehydrated because:

• A. They lose their outer membrane
• B. They trap the crystal violet-iodine complex
• C. They have high lipid content
• D. They lose the peptidoglycan layer

Hint:

Gram positive bacteria have thick peptidoglycan layers, and lower lipid content in their cell walls, while gram-negative bacteria have thin peptidoglycan layers and higher lipid content. This difference in the cell wall leads to a differential staining as the alcohol washes away the lipid and the crystal violet stain.

Answer 1

The Correct Option is A

Gram-positive bacteria retain the purple stain in Gram staining due to their thick peptidoglycan layer, which has low lipid content. When treated with alcohol:
• The alcohol dehydrates the peptidoglycan layer, causing it to shrink and trap the crystal violet-iodine complex.
• Gram-negative bacteria, with higher lipid content, lose the outer membrane and the stain during alcohol treatment.
This property differentiates Gram-positive and Gram-negative bacteria in microbiological analysis.