The purpose of a mordant in the Gram stain is to
A) make the bacterial cells larger.
B) make gram- negative cells visible.
C) remove the simple stain.
D) prevent the crystal violet from leaving the cells.
E) make the flagella visible.

Question

Quizplus · Accepted Answer

The purpose of a mordant in the Gram stain is to prevent the crystal violet from leaving the cells by forming a complex with the dye. This is important because the subsequent decolorization step can remove the crystal violet from some bacteria, but those that have formed a tight complex with the mordant will retain the purple color and appear as Gram-positive. Without the mordant, the results of the Gram stain would not be reliable. Therefore, choice D is the correct answer.

The Purpose of a Mordant in the Gram Stain Is