The Ciliate Count Challenge

9/28/17

Purpose: The purpose of this activity is to practice performing serial dilutions and using micropipettes to determine the concentration in cells/mL. After counting the cells, use the information to report the mean and standard deviation among the counts of your peers.

Procedure:

•  Using media and Tetrahymena culture, make a 1:10 dilution series to a 1:10,000 in labeled microfuge tubes.
• Add a small amount of your sample to the tube marked 0-.
• Add 90 microliters of diluent to each of the rest of the tubes.
• Add 10 microliters of undiluted sample to the 10^-1 tube and mix.
• Add 10 microliters of 10^-1 sample to the 10^-2 tube and vortex. Repeat for each tube.
• Place a 5 microliter drop of each solution on a concavity slide and count the number of cells at 4x power.
• Report the replicate, mean, and the standard deviation.
• Use the 1M solution of NaCl to make dilutions and determine the minimum amount of NaCl that will cause an immediate effect on the Tetrahymena.
  • Differing amounts of 1M NaCl was added to 5 microliters of tetrahymena culture.

Observations:

10^-1 Average cell count per microliter = 5.8 cells per microliter

Average cells per microliter in undiluted sample = 58 cells

Average cells per milliliter in undiluted sample = 58,000 cells

The following amounts of 1M NaCl were added to 5 microliters of Tetrahymena culture and the following observations were made.

5 microliters = All tetrahymena died immediately.

3 microliters = All tetrahymena died immediately.

1.5 microliters = All tetrahymena died immediately.

0.75 microliters = Tetrahymena survived for about 3-4 minutes then died.

Conclusion: