MacConkey Agar Plates Represent ________ Medium

Question

MacConkey agar plates represent ________ medium.
A) a minimal
B) a selective
C) a differential
D) both a differential and a selective
E) both a minimal and a selective

Accepted Answer

MacConkey agar plates are both differential (able to distinguish between different microorganisms based on differences in their biochemical reactions) and selective (able to selectively isolate gram-negative bacteria while inhibiting the growth of gram-positive bacteria). This is due to the presence of bile salts and crystal violet in the medium, which inhibit the growth of gram-positive bacteria, and the inclusion of lactose and neutral red, which allow for the differentiation of lactose-fermenting and non-lactose-fermenting gram-negative bacteria based on the color of the colonies that grow on the agar.