Question

2. Suppose that a broth culture has 52 million bacteria per milliliter. A serial dilution is made using three bottles of 99 milliliters each. One (1.0) mL is transferred from the sample to the first bottle (A); then 1 mL is transferred from the first bottle to the second (B); and then 1 mL is transferred from the second bottle to the third (C). From the third bottle 0.1 mL is transferred to a spread plate. How many colonies would you expect to find on this plate

Answer 1

Answer:

Approximately 5.2 colonies

Explanation:

Given that the original broth culture has 52 million bacteria/ml. = 52 * 10^6 bacteria/ml

It is diluted 100 times in bottle A = 52 * 10^4 bacteria/ml

It is diluted 100 times again in bottle B = 52 * 10^2 bacteria/ml

It is diluted 100 times again in bottle C = 52 bacteria/ml

From bottle C, 0.1 ml is plated = 5.2 bacteria

Since a single colony on plate represents a single bacteria in solution, approximately 5.2 colonies will be observed on plate.