At the end of microbiology lab, you decide to practice your Gram-staining skills. The teaching assistant has no fresh cultures b
ut says you may use a plate she prepared several weeks ago. You find the correct plate in the refrigerator (labeled B.s. for Bacillus subtilis) and note that the colonies appear raised, dull, and wrinkled. This is just as you recall, so you get to work. After staining, you examine your slide under oil immersion and see that the cells are stained pink. What most likely accounts for this coloring?
Grams staining i a staining method used to classify bacteria into two main classes. Gram positive and Gram negative.
They are differentiated according to the ability of their cell wall to retain the primary stain color of the crystal violet stain or the counter stain pink.
Bacillus subtilis is a Gram positive bacteria hence it is supposed to stain purple.
Therefore, when it stained pink is an error. it shows loss of the cell wall integrity due to old age, overdecolorization or over fixing with heat.
