Counted bacterial colonies on plates are used as a practical proxy for estimating bacterial numbers because individual bacteria are too small to count directly, while each colony typically arises from a single viable cell or a cluster that grew into a visible mound. Key points

• Colony-forming units (CFUs) are the standard metric: CFU refers to viable cells capable of forming a colony, not the total cell count. Counting colonies after plating diluted samples yields CFU per given volume or per plate, which then is back-calculated to estimate the original concentration in the sample. This approach accounts for clumping by ensuring dilutions where single cells (or minimal multiples) are spread on plates.

• Dilution and plating strategies are essential: because most samples contain far more cells than plates can accommodate, serial dilutions are prepared and small volumes from each dilution are plated. The dilution factor, along with the plated volume, is used to compute the original CFU/mL in the sample. This is a foundational method in microbiology for obtaining countable plates.

• Direct counting of individual bacteria on plates is not feasible: bacteria are microscopic, and even with streaking and isolation techniques, distinguishing single cells from tiny clusters on dense plates is unreliable, so colonies are used as a practical surrogate. The answer to the prompt’s true/false framing is that it is true that counting individual bacteria on culture plates is difficult, hence colonies are used to infer counts.

• Alternatives and refinements exist: modern approaches include high-throughput or image-based methods (e.g., automated colony counters, growth-kinetics-based estimations like virtual colony counts), which aim to reduce manual counting errors and speed up quantification, while still relying on the CFU concept or equivalent proxies.

Putting it succinctly: Yes, it is difficult to count individual bacteria on culture plates due to their small size and tendency to form colonies or clumps; therefore, colony counts (CFUs) after appropriate dilutions are used to estimate bacterial numbers in a sample. This method balances accuracy with practicality and remains a standard in microbiology.