You observed that a high dilution of a young culture was plated on a medium know

Question

You observed that a high dilution of a young culture was plated on a medium known to support its growth, but after 48 hours of incubation, the plate showed no growth. Give two possible explanations for these results. 6 Dilution Problems 1. What is the final dilution obtained after each dilution series shown below? Express each answer in exponential numbers. a. 1:10, 1:10, and 1:100: b, 10-, 10-I, and 10% c. 10 and 10 2. Determine the number of cells per milliliter of the original culture when the total number of colonies and the total dilutions are as follows Viable no. in original culture (CFU/ml) Plate count Final dilution 1:100 1:1,000,000 37 147 10-5 221 10-7 Show one sample calculation here:

Explanation / Answer

6.

Reason 1: The high dilution may have highly decreased the bacterial count in the young culture. Because of the very low frequency of the bacteria in the culture, the microorganisms did not grow on a media where the growth was supported.

Reason 2: The bacterial culture may be dead. Most of the time the dead cells and living cells may look alike. Another reason may be that the bacterial culture may have not been plated correctly and contamination by other bacteria or fungi may have occurred.

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