Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Colony-forming unit (CFU) is a measure used to estimate the number of viable microorganisms in a sample. It represents individual cells or groups of cells that can form a colony when cultured under suitable conditions.
5 Must Know Facts For Your Next Test
The CFU count is crucial for quantifying bacterial growth and contamination levels in microbiological studies.
CFUs are typically expressed as CFU per milliliter (CFU/mL) for liquids or per gram (CFU/g) for solids.
Not all microbes will form colonies; some may be viable but non-culturable (VBNC).
A single CFU can originate from one cell, a pair, chain, or cluster of cells.
CFUs are used in various applications, including food safety, water quality testing, and clinical diagnostics.
Review Questions
Related terms
Plate Count Method: A technique to count the number of CFUs on an agar plate.
Viable But Non-Culturable (VBNC): Microorganisms that are alive but cannot be cultured using standard methods.
Serial Dilution: A stepwise dilution process used to reduce the concentration of microorganisms to facilitate counting.