Which term describes the group that includes streak plate, pour plate, and spread plate methods?

• A. Streak plate techniques
• B. Pour plate techniques
• C. Isolation techniques
• D. Spread plate techniques

Answer: (C)

Isolating bacteria to obtain a pure culture is achieved by methods that spread cells thinly on or in a solid medium so discrete colonies can form. Streak plate, pour plate, and spread plate are all designed for this purpose, each manipulating how cells are placed to separate them so that individual cells grow into distinct colonies. In a streak plate, you gradually dilute the sample across the surface to achieve separation; in a pour plate, you mix a diluted sample with molten agar so colonies develop within the medium; in a spread plate, you spread a diluted suspension across the surface to distribute cells evenly. Because they share the goal of producing isolated colonies for a pure culture, the broad category that includes all of these methods is isolation techniques. The other terms name a single method rather than the overall approach.