Which of the following basic dyes is commonly used as the counterstain in the Gram stain procedure?
A
Crystal violet
B
Malachite green
C
Methylene blue
D
Safranin
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Understand the Gram stain procedure, which involves a primary stain, a mordant, a decolorizer, and a counterstain to differentiate bacterial cell wall types.
Identify the primary stain used in the Gram stain, which is Crystal violet, staining all cells initially.
Recognize that after decolorization, Gram-positive bacteria retain the Crystal violet, while Gram-negative bacteria lose it and need a counterstain to be visible.
Recall that the counterstain is a basic dye that stains the decolorized Gram-negative bacteria, providing contrast to the purple Gram-positive cells.
Know that Safranin is the commonly used counterstain in the Gram stain procedure, staining Gram-negative bacteria pink/red.