Final answer:
The pour plate and spread plate methods are used to estimate the number of microbes in a sample via serial dilution and colony counts. They provide results as CFU/mL and are considered reliable and effective despite certain limitations.
Step-by-step explanation:
The pour plate and the spread plate are quantitative techniques used to determine the number of microbes in a given sample. These methods involve a process of serial dilution followed by either mixing the sample with warm liquid agar before pouring into a Petri dish in the case of the pour plate method, or pouring the sample onto solid agar and spreading it out for the spread plate method.
The resulting colonies are counted to provide an estimate of the number of cells in the original volume sampled. When a sample’s microbial concentration is too low, microbiologists may use the most probable number (MPN) method or concentrate the sample before plating via membrane filtration.
Despite various methods available, the viable plate count remains a traditional and effective means to estimate live bacterial numbers, expressed as colony-forming units per milliliter (CFU/mL).