In microbiology, what best defines a pure culture?

• A. A culture taken directly from a clinical specimen before any isolation steps are performed
• B. A culture that contains only bacterial cells and no viruses, fungi, or protozoa
• C. A population of microorganisms consisting of a single species (or strain) grown without contamination from other species
• D. A mixed population of different microbial species grown together in the same medium

Answer: (C)

Verified step by step guidance

1. Understand that a pure culture in microbiology refers to a population of microorganisms that are all of the same species or strain, without contamination from other species.
2. Recognize that a culture taken directly from a clinical specimen is usually mixed and contains multiple species, so it is not a pure culture.
3. Note that excluding viruses, fungi, or protozoa does not define a pure culture, since the key factor is the presence of only one microbial species or strain.
4. Identify that a mixed population of different microbial species grown together is the opposite of a pure culture.
5. Conclude that the best definition of a pure culture is a population of microorganisms consisting of a single species (or strain) grown without contamination from other species.