Question

which reagent is responsible for staining gram - negative bacteria pink?
a) 95% ethyl alcohol
b) crystal violet
c) safranin
d) iodine

Explanation:

In Gram - staining, safranin is the counter - stain. After the decolorization step (using 95% ethyl alcohol), Gram - negative bacteria lose the crystal violet - iodine complex (crystal violet is the primary stain and iodine is the mordant). Then safranin stains the Gram - negative bacteria pink. 95% ethyl alcohol is for decolorization, crystal violet is the primary stain (stains both Gram - positive and Gram - negative initially), and iodine is the mordant.

Answer:

C. Safranin