Some Practice Problems for Project 1 (these will NOT be graded) Note: Draw these

Question

Some Practice Problems for Project 1 (these will NOT be graded) Note: Draw these problems out as you work them, it will help you visualize the dilution series 1. You take 100 1 of a stock solution containing 10,000,000 (1X107) cells/ml and add it to 900 1 water to make dilution #1. From dilution #1 you take 10 1 and add it to 990 1 of water to make dilution #2. From dilution #2 you take 10 1 and add it to 990 1 of water to make dilution #3. You spread 100 l of dilution #3 on a bacterial growth plate. A. what is the concentration of dilution #2. B. How many bacterial colonies do you expect to see develop on the bacterial growth plate?

Explanation / Answer

Ans.1(A) Concentration of the Dilution #2 is 1x104 cells / ml.

explanation: Dilution of the stock solution

dilution 1# 10-1 dilution 2# 10-3   dilution 3# 10-5

concentrationof dilution 2# = concentration of stock solution x dilution factor

107 x103 =104 cells /ml

1(B)

No. of bacteria colonies grows in the media as they are present in the final aliquot of the dilution used for plating.

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