Question

If you forgot to perform steaming step during the endospore stain, what color would you expect spores to appear after (otherwise accurate) completion of the stain? A) Pink B) Purple C) Green D) Colorless E) Not enough information to tell

Answer 1

A. Pink

Endospores possess a permeability barrier which prevents dyes from entering to stain its structure. In order to destroy this barrier, heat is used. Through heat fixing, the cortex of the endospore is penetrated allowing for the dye to interact with the petodoglycan giving the characteristic green color to the spores from the stain Malachite green. If the steaming step is not performed, the stain Malachite green will not penetrate the spore and hence the whole cell will retain the color of the counter stain Safranin alone i.e., the whole cell will appear pink in color without the endospore being separately differentiated.