Which technique involves mixing a diluted sample with melted agar and pouring into sterile Petri dishes?

Which technique involves mixing a diluted sample with melted agar and pouring into sterile Petri dishes?

• A. Streak plate technique
• B. Spread plate technique
• C. Drop technique
• D. Pour plate technique

Answer: (D)

Pour plate technique is being tested here. In this method, you mix a diluted sample with melted agar and pour the mixture into sterile Petri dishes, allowing the agar to solidify. The cells are embedded within the agar as it hardens, so colonies can form not only on the surface but also within the deeper layers after incubation. This approach is useful for counting viable cells (CFUs) across a range of densities, since embedding in the agar helps accommodate more cells than surface-only methods. It differs from streak plating, which distributes cells by dragging them across the surface to separate colonies, and from spread plating, which places a diluted sample on the surface of already solidified agar to let colonies form on the surface. The drop plate technique, by contrast, places small drops on the surface rather than mixing with the agar.

Pour plate technique is being tested here. In this method, you mix a diluted sample with melted agar and pour the mixture into sterile Petri dishes, allowing the agar to solidify. The cells are embedded within the agar as it hardens, so colonies can form not only on the surface but also within the deeper layers after incubation. This approach is useful for counting viable cells (CFUs) across a range of densities, since embedding in the agar helps accommodate more cells than surface-only methods. It differs from streak plating, which distributes cells by dragging them across the surface to separate colonies, and from spread plating, which places a diluted sample on the surface of already solidified agar to let colonies form on the surface. The drop plate technique, by contrast, places small drops on the surface rather than mixing with the agar.