Serial Dilutions & Micropipetting

9/21/2017

Purpose: The purpose of this activity was to learn how to use a micropipette as well as learn how to use serial dilutions to estimate the number of cells in a given solution.

Procedure:

• Using media and the Tetrahymena culture, make a 1:10 dilution series to a 1:10,000 dilution in labeled microfuge tubes.
  • A 1:10 dilution is 10 microliters of tetrahymena into 90 microliters of media.
• Use the serial dilution procedure to create a 1:10,000 dilution.
• Be sure to place 10 microliters of each solution into each descending tube and don’t forget to mix the solution after adding the 10 microliters.
•  Place a 5 microliter drop of each solution on a concavity slide and count the number of cells at 4x power under the compound microscope.
• Find the dilution that has an easily countable number of cells (about 10-20) and repeat this procedure 3 times to ensure accuracy.
• Use the equation : Average cells in 5 microliters/ dilution factor x 1000 microliters = x cells/mL

Observations:

Zero = Too many cells to count

10^-1 = 38 cells

10^-2 = 16 cells

10^-3 = 3 cells

10^-4 = 1 cell

Conclusion: Learning how to use micropipettes and how to perform serial dilutions is crucial for laboratory activities. Counting cells in a solution will be very helpful for our future experiments. For example, it would not be possible to determine the effect of a toxicant if one was unable to determine how many cells were killed or how many survived. The next step for our lab is to begin our tetrahymena experiments.