Toxicity Assay

10/5/17

Purpose: The purpose of this activity was to begin our experiment that we will conduct for the semester. Section 1105-34 will be testing the affects of NH4Cl  on tetrahymena survival. NH4Cl, a common component of fertilizer is very relevant in our study of the affects of toxicants in the soil environment.

Procedure:

1. Pipette 450 microliters of PPT into 3 wells.
2. Pipette 50 microliters of well-mixed stock culture into the 450 microliters of PPT media in well 1.
3. Mix gently.
4. Transfer 50 microliters of 1:10 dilution into the 1:100 well. Mix.
5. Transfer 50 microliters of 1:100 dilution into the 1:1000 well. Mix.
6. Observe Tetrahymena in each well and choose the dilution that will allow you to count between 10-30 cells in a 10 microliter drop.
7. Dilute the culture to 1000 cells/mL making enough culture for each person in the group to use about 6 mL.
8. Obtain solution with treatment of 75 treatment of NH4Cl.
9. Make the dilution in a 50 mL test tube. Add the required amount of stock culture and add PPT media to the 20 mL graduation mark on the tube.
10. Add treatment to the culture and dilute the culture and be sure to add an equal amount of water to the control wells.
11. Record all observations and safely store your plate for future observation.
12. Return to lab to count cells.
13. Add 20 microliters of iodine to each well and take 3 cell counts for each well using 10 microliter drops.
14. Record counts in cells/mL on the spreadsheet.

Observations/Data

Average cell count: 17 cells

Count per microliter: 1.7

Dilution factor: 1:100

Cells/microliter: 170

Cells per mL in stock : 170,000

Average : 81,118

Standard Deviation: 64,396

Average cells per mL 1 Treatment : 1067

Average cells per mL 2 Treatment : 1400

Average cells per mL 3 Treatment : 766

Average cells per mL 1 Control : 8660

Average cells per mL 2 Control : 9330

Average cells per mL 3 Control : 5000

Conclusion: We collected data as a class and are ready to begin our experiments. The different groups in the class have different treatments and an overlying conclusion will be formed once all experiments have finished.