In the context of plating methods, what is a bacterial colony?

• A. A single bacterial cell observed under a light microscope after Gram staining
• B. A sterile area of agar where bacterial growth has been inhibited by an antibiotic disk
• C. A visible mass of bacterial cells on solid media that typically arises from a single progenitor cell (a colony-forming unit, CFU)
• D. A liquid culture containing a mixed population of multiple bacterial species grown in broth

Answer: (C)

Verified step by step guidance

1. Understand that in microbiology, a bacterial colony refers to a visible cluster of bacterial cells grown on a solid medium, such as agar.
2. Recognize that each colony typically originates from a single progenitor cell or a group of cells known as a colony-forming unit (CFU), which multiply to form the visible mass.
3. Differentiate a bacterial colony from other concepts such as a single bacterial cell (which is microscopic and not visible to the naked eye) or a sterile zone on agar (which indicates inhibition, not growth).
4. Note that a bacterial colony is distinct from a liquid culture, which contains bacteria suspended in broth and is not visible as discrete masses.
5. Summarize that a bacterial colony is essentially a macroscopic growth on solid media representing the descendants of one or a few bacterial cells, making it a fundamental unit for isolating and studying bacteria.