Multiple Choice
In a completed Gram stain procedure, what is the final color of Gram-negative bacteria when observed under a microscope?
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9. Microscopes
Gram Stain
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
In the Gram stain procedure, crystal violet is the __________.
A
decolorizer
B
primary stain
C
counterstain
D
mordant
Verified step by step guidance1
Understand the purpose of each reagent in the Gram stain procedure: the primary stain, mordant, decolorizer, and counterstain each have distinct roles.
Identify the role of crystal violet in the procedure. Crystal violet is the first dye applied to the bacterial smear, which stains all cells initially.
Recognize that the primary stain is the initial dye that colors all cells, allowing differentiation later based on cell wall properties.
Recall that the mordant (usually iodine) forms a complex with crystal violet to fix the dye inside the cells, especially Gram-positive bacteria.
Note that the decolorizer (usually alcohol or acetone) removes the stain from Gram-negative cells, and the counterstain (such as safranin) stains the decolorized cells to make them visible.
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