Final answer:
The spread plate method is a microbiological technique for isolating and counting viable bacterial cells from a liquid sample, involving a serial dilution, plating on agar, and spreading to form isolated colonies.
Step-by-step explanation:
The spread plate method is a technique used in microbiology to plate a liquid sample containing bacteria for the purpose of isolating and counting viable cells. The process begins with a serial dilution of the bacterial culture, ensuring that the concentration of bacteria is reduced to a level that will result in distinct colonies after incubation. A small volume of the diluted sample is then transferred to an agar plate. Using a sterilized spreading tool or loop, the sample is uniformly spread across the surface of the agar. It is important to flame the loop between streaks to ensure sterility. The plate is then incubated to allow the bacteria to grow into separate colonies. The end result is a plate with individual colonies that can be counted to estimate the number of viable bacteria in the original sample.