Which of the following correctly lists the steps of the Gram stain procedure in the proper order?
A
Iodine, crystal violet, safranin, alcohol
B
Crystal violet, iodine, alcohol, safranin
C
Safranin, alcohol, crystal violet, iodine
D
Alcohol, safranin, iodine, crystal violet
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1
Understand that the Gram stain is a differential staining technique used to classify bacteria into Gram-positive and Gram-negative based on their cell wall properties.
Recall the correct sequence of the Gram stain procedure: first, apply the primary stain (crystal violet) to color all cells.
Next, add the mordant (iodine), which forms a complex with crystal violet, helping it to fix inside the cell wall.
Then, apply the decolorizer (alcohol or acetone-alcohol), which removes the stain from Gram-negative cells but not from Gram-positive cells due to their thicker peptidoglycan layer.
Finally, apply the counterstain (safranin), which stains the decolorized Gram-negative cells pink/red, while Gram-positive cells remain purple.