Question

what does the term acid-fast mean?

a) while most bacteria are stained by acid-alcohol, some are not.

b) Using acid is a quicker way to stain most bacteria.

c) Acid-alcohol stains some bacteria a special color based on their peptidoglycan layer.

d) Acid-alcohol is used to keep the stain from leaving a bacteria cell

Answer 1

while most bacteria are stained by acid-alcohol, some are not (a)

Note: The acid fast is a kind of differential stain which distinguishes bacteria having waxy cell walls (mycolic acid) which can resist decolorization with acid alcohol. In the staining process carbol fuchsin is the primary stain which contains phenol to solubilize the cell wall. All cells take up the primary stain. The cells are then decolorized with acid alcohol which decolorizes all cells except the acid fast cells. Methylene blue is then used as counterstain to decolorized cells. Consequently, the acid fast cells will be red to pink while non-acid fast cell will appear blue.