Which of the following reagents is used to stain gram negative cells pink (or red) in the gram stain?

• A. Iodine.
• B. Safranin.
• C. Crystal violet.
• D. Decolorizing agent.

Answer: (B)

Verified step by step guidance

1. Understand the Gram staining process: Gram staining is a differential staining technique that distinguishes between Gram-positive and Gram-negative bacteria based on the composition of their cell walls.
2. Identify the primary stain: The process begins with the application of crystal violet, which stains all cells purple.
3. Apply the mordant: Iodine is used as a mordant to form a complex with crystal violet, helping it adhere to the cell walls.
4. Use the decolorizing agent: Alcohol or acetone is used to decolorize the cells. Gram-positive cells retain the crystal violet-iodine complex, while Gram-negative cells do not.
5. Apply the counterstain: Safranin is used as a counterstain to color the decolorized Gram-negative cells pink or red, allowing them to be distinguished from the purple Gram-positive cells.