In microbiology, what best describes a pure culture?

• A. A mixed population of multiple microbial species growing together in the same medium
• B. A population of microorganisms consisting of a single species (or strain) with no contaminating organisms present
• C. A microbial culture that has been incubated long enough to reach the stationary phase of growth
• D. A microbial culture that contains only nonpathogenic organisms

Answer: (B)

Verified step by step guidance

1. Understand the definition of a pure culture in microbiology: it refers to a population of microorganisms that are all genetically identical or belong to the same species or strain.
2. Recognize that a pure culture must be free from contamination, meaning no other microbial species or strains are present alongside the target organism.
3. Differentiate a pure culture from a mixed culture, which contains multiple species growing together in the same medium.
4. Note that the growth phase (such as stationary phase) or pathogenicity (whether organisms are pathogenic or nonpathogenic) does not define a pure culture.
5. Conclude that the best description of a pure culture is a population of microorganisms consisting of a single species (or strain) with no contaminating organisms present.