Which of the following lists the correct order of the four reagents used in the Gram stain procedure?

• A. Crystal violet, iodine, alcohol, safranin
• B. Iodine, crystal violet, safranin, alcohol
• C. Safranin, alcohol, iodine, crystal violet
• D. Alcohol, crystal violet, safranin, iodine

Answer: (A)

Verified step by step guidance

1. Understand that the Gram stain procedure is a differential staining technique used to classify bacteria into Gram-positive and Gram-negative based on their cell wall properties.
2. Recall the four main reagents used in the Gram stain: crystal violet (primary stain), iodine (mordant), alcohol (decolorizer), and safranin (counterstain).
3. Recognize the correct sequence of applying these reagents: first, apply crystal violet to stain all cells purple; second, add iodine which forms a complex with crystal violet to fix the dye; third, use alcohol to decolorize, washing out the dye from Gram-negative cells but not Gram-positive; finally, apply safranin to counterstain the decolorized Gram-negative cells pink/red.
4. Match this sequence to the options given to identify the correct order: crystal violet, iodine, alcohol, safranin.
5. Confirm that the other options do not follow the logical staining steps and thus are incorrect.