Which term describes a group of identical bacterial cells growing together on a solid medium?

Which term describes a group of identical bacterial cells growing together on a solid medium?

• A. Colony
• B. Biofilm
• C. Clone
• D. Culture

Answer: (A)

On a solid growth medium, a visible cluster of bacteria that comes from a single progenitor cell is called a colony. Because all cells in that colony descend from the same ancestor, they are genetically identical, forming a clonal group. This visible colony on an agar plate is what microbiologists use to count viable cells (as colony-forming units) and to obtain pure cultures. A biofilm is a surface-attached community embedded in a matrix, usually not a single, discrete mound on a plate. A clone describes genetically identical cells, but doesn’t specify the physical grouping on a solid medium. A culture is a general term for growing microbes in a medium, which can be liquid or solid, and doesn’t specify the discrete, isolated growth seen as a colony.

On a solid growth medium, a visible cluster of bacteria that comes from a single progenitor cell is called a colony. Because all cells in that colony descend from the same ancestor, they are genetically identical, forming a clonal group. This visible colony on an agar plate is what microbiologists use to count viable cells (as colony-forming units) and to obtain pure cultures. A biofilm is a surface-attached community embedded in a matrix, usually not a single, discrete mound on a plate. A clone describes genetically identical cells, but doesn’t specify the physical grouping on a solid medium. A culture is a general term for growing microbes in a medium, which can be liquid or solid, and doesn’t specify the discrete, isolated growth seen as a colony.