The pour plate method counts viable microorganism colonies by using serial dilution. A diluted sample is poured into a petri dish, combined with warm agar and gently swirled. Following solidification, the plate is incubated at the ideal temperature (typically at 37°celsius for 24-48 hours). Next, observable microbial colonies develop on the plate, allowing for counting. The CFU/mL is calculated using the formula:

CFU/mL= Total number of colonies * dilution factor/volume of sample used (aliquot)

To summarize, the pour plate relies on the idea that when a mixture of microorganisms and agar medium is incubated, each viable microorganism will proliferate independently. This results in the formation of individual colonies.