Question

Which of the following is TRUE about staining?

Select one:
a. There are two stages in stains
b. A simple stain will stain all bacteria red
c. Ethanol acts as a decolorizer
d. Crystal violet is a secondary stain

Answer 1

c) Ethanol acts as a decolorizer in staining, selectively removing stain from Gram-negative cells. Hence, c) is correct.

Step-by-step explanation:

The true statement about staining is option c: Ethanol acts as a decolorizer. In the Gram staining technique, the addition of ethanol serves as a decolorizing step. It selectively removes the stain from only the Gram-negative cells, while the Gram-positive cells retain the primary stain, which is crystal violet.

This results in the differentiation of gram-positive and gram-negative bacteria. The decolorized cells are then counterstained with a secondary stain, safranin, which stains them pink, whereas the gram-positive cells remain purple. Therefore, ethanol acts as a decolorizer in the staining process.