Question

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

Explanation:

In Gram - staining, crystal violet is the primary stain (colors all bacteria purple). Iodine is a mordant that fixes the crystal violet. 95% ethyl alcohol is the decolorizing agent. Gram - negative bacteria lose the crystal violet - iodine complex during decolorization. Safranin is the counter - stain. It stains the Gram - negative bacteria (which have lost the primary stain) pink.

Answer:

d) Safranin