Question

Role of Gram's Iodine in gram staining technique:

• A. Enhances the binding of crystal violet to cell wall
• B. Blocks the binding of crystal violet to cell wall
• C. Neither blocks nor enhances the binding of crystal violet to cell wall
• D. Enhances the ability of alcohol to remove the binding of crystal violet to cell wall

Hint:

Gram's iodine is used in the Gram staining process to form a crystal violet-iodine complex, which strengthens the color retention in Gram-positive bacteria's thick peptidoglycan layer.

Answer 1

The Correct Option is A

Gram's iodine plays an essential role in the Gram staining technique. When performing the Gram stain, crystal violet, the primary stain, is applied to bacterial cells. Gram's iodine acts as a mordant, which forms a complex with crystal violet. This iodine-crystal violet complex gets trapped in the thick peptidoglycan layer of Gram-positive bacteria, enhancing the binding of crystal violet to the cell wall.
Iodine's role is crucial in intensifying the color of the stain and aiding in the retention of the crystal violet within the cell wall, making the Gram-positive bacteria appear purple. This is in contrast to Gram-negative bacteria, where the thinner peptidoglycan layer does not retain the iodine-crystal violet complex, leading to the use of a counterstain (usually safranin) to visualize them as red or pink.
Without the iodine step, the crystal violet would not form such a stable complex, and the staining results would be inaccurate. Therefore, Gram's iodine enhances the binding of crystal violet to the cell wall, making it a vital component of the Gram staining process.