What is a colony forming unit (CFU) in this context?

What is a colony forming unit (CFU) in this context?

• A. The measurable number of colonies formed on the agar plate, used to infer microbial numbers.
• B. A single bacterial cell that forms a colony.
• C. A measure of the total biomass in the culture.
• D. A non-viable cell that cannot form colonies.

Answer: (A)

The concept being tested is that a colony forming unit (CFU) is a unit used to quantify viable microorganisms by counting colonies on an agar plate. When you plate a diluted sample and incubate, each visible colony arises from a viable organism (or sometimes a small cluster of organisms) that was able to grow and reproduce into a colony. By counting these colonies, you estimate how many viable microbes were in the original sample, usually expressed as CFU per mL or per gram after accounting for the dilution factor. This makes CFU a measure of live, colony-forming cells, not total biomass or dead cells. It’s also worth noting that one CFU can originate from more than one cell if cells were in a clump, so CFU is an estimate of viable cell numbers rather than an exact count of single cells.

The concept being tested is that a colony forming unit (CFU) is a unit used to quantify viable microorganisms by counting colonies on an agar plate. When you plate a diluted sample and incubate, each visible colony arises from a viable organism (or sometimes a small cluster of organisms) that was able to grow and reproduce into a colony. By counting these colonies, you estimate how many viable microbes were in the original sample, usually expressed as CFU per mL or per gram after accounting for the dilution factor. This makes CFU a measure of live, colony-forming cells, not total biomass or dead cells. It’s also worth noting that one CFU can originate from more than one cell if cells were in a clump, so CFU is an estimate of viable cell numbers rather than an exact count of single cells.