Which method is used to grow separate bacterial colonies by plating serial dilutions of a liquid culture?

The Spread Plate Technique is specifically designed to grow separate bacterial colonies from a diluted liquid culture. In this method, a small volume of a diluted sample is spread evenly across the surface of an agar plate using a sterile spreading tool, often referred to as a spreader or glass rod. This technique allows individual bacterial cells to be evenly distributed over the agar surface, leading to the formation of isolated colonies as they grow from single cells.

The purpose of using serial dilutions prior to applying the sample to the agar plate is to reduce the concentration of bacterial cells in order to achieve well-separated colonies. By performing dilutions, the chances of overcrowding within the colonies are minimized, which is crucial for accurate colony counting and identification. Each visible colony that develops can be traced back to a single bacterial cell from the original culture, making this method particularly useful for quantitative microbiology.

In contrast, other plating methods serve different purposes: the Pour Plate Technique involves mixing diluted cultures with molten agar and pouring it into a plate, which can lead to colonies developing both on the surface and within the agar, while the Streak Plate Technique is primarily used to isolate and purify bacterial strains rather than quantification. The Direct Plating Method does not necessarily involve serial dilutions and