What is the best explanation for a Gram-negative bacterium appearing purple after performing a Gram stain?
A) The safranin was not applied.
B) The decolorizer was not applied.
C) The iodine was not applied.
D) The crystal violet was not applied.
E) The stain was properly performed.

Question

Quizplus · Accepted Answer

Gram-negative bacteria appear purple after a Gram stain if the decolorizer (usually alcohol or acetone-alcohol) was not applied. Normally, the decolorizer removes the crystal violet from the thinner peptidoglycan layer of Gram-negative bacteria, allowing them to take up the counterstain (safranin) and appear pink/red. If the decolorizer step is skipped, the crystal violet is not removed, and the bacteria appear purple, similar to Gram-positive bacteria.

What Is the Best Explanation for a Gram-Negative Bacterium Appearing