Apollon Bacteriology Complete Practice Test 2026

In the pour-plate method, the primary purpose is to quantify the number of viable bacteria in a sample. When you mix the sample with molten agar and pour it into a petri dish, the agar solidifies around the bacteria, allowing for colony formation. The amount of agar added does not alter the dilution factor of the original sample because dilution is determined by the ratio of the sample volume to the total volume of medium. Therefore, regardless of how much agar you use, the original sample's concentration remains unchanged as long as the sample volume remains constant in relation to the agar. This means the dilution remains consistent, and thus, the correct assessment is that dilution is not affected by the amount of agar added in this context.