MacConkey agar is
A)a selective agar.
B)a differential agar.
C)a selective and differential agar.
D)used to distinguish between bacteria by the type of hemolysis observed.

Question

Quizplus · Accepted Answer

MacConkey agar is both a selective and differential agar. It is selective for gram-negative bacteria because of the presence of crystal violet and bile salts, which inhibit the growth of gram-positive bacteria. It is differential because it contains lactose and a pH indicator. Lactose-fermenting bacteria will produce acidic byproducts, causing the agar to turn pink. Non-lactose fermenting bacteria will not produce byproducts, causing the agar to remain its normal color.

MacConkey Agar Is