10 You are given a test tube containing 5 mL of a solution w

10) You are given a test tube containing 5 mL of a solution with 8.4 x 107 cells/mL. You are to produce a solution that contains less than 100 cells/mL. What serial dilutions must you perform in order to arrive at the desired result? (Hint: Plan to perform your dilutions in 1.5 mL microcentrifuge tubes, since you will only plate a volume of ~1 mL. After determining your overall dilution factor, separate this out into several serial dilutions of 1:10 or 1:100.)

Solution

Method 1

Method 2

1 ml of original solution + 9 ml of water = 8.4 x 10⁵ cells/ml.

1 ml of second solution + 9 ml of water = 8.4 x 10³ cells/ml.

1 ml of third solution + 9 ml of water = 8.4 x 10¹ or 84 cells/ml.

100 µl of original solution + 900 µl of water = 8.4 x 10⁵ cells/ml.

100 µl of second solution + 900 µl of water = 8.4 x 10³ cells/ml.

100 µl of third solution + 900 µl of water = 8.4 x 10¹ or 84 cells/ml.

Method 2 is the answer, for your question. For easy understanding, I have given Method 1.

With Method 2, you will get exactly 1ml of diluted sample with 84 cells/ml and that you can directly plate and this dilution you can do using 1.5mL vial.