You are performing a Gram stain on gram- positive bacteria and you stop after the addition of the counterstain. What is the appearance of the bacteria at this point?
A) colorless
B) brown
C) purple
D) red

Question

Quizplus · Accepted Answer

The counterstain used in Gram staining is usually safranin or basic fuchsin, which stains Gram-negative bacteria red or pink, while the previously stained Gram-positive bacteria will remain purple. Therefore, the appearance of the bacteria at this point would be purple if they are Gram-positive.

You Are Performing a Gram Stain on Gram- Positive Bacteria