A culture medium on which only gram- positive organisms grow and a yellow halo surrounds Staphylococcus aureus colonies is called a(n)
A) enrichment culture.
B) differential medium.
C) selective medium.
D) selective and differential medium.
E) differential and enrichment culture.

Question

Quizplus · Accepted Answer

A selective medium is one that only allows certain types of organisms to grow, in this case only gram-positive organisms. A differential medium is one that distinguishes between different types of organisms, in this case by the presence of a yellow halo around Staphylococcus aureus colonies. Therefore, the culture medium described is both selective and differential, making choice D the best answer.

A Culture Medium on Which Only Gram- Positive Organisms Grow