Discover a New Antibiotic
A Test For Antiprotozoan Drugs

Christine L.Case


Sample data

When a few cells are inoculated into a culture medium, and the population is counted at intervals, it is possible to plot a population growth curve that shows the growth of cells over time. A good drug might prolong lag phase, increase the generation time during log phase, or cause death.


A protozoan culture &
Sterile protozoan culture media

Leaves or other plant parts to test

Mortar and pestle


Pasteur pipettes (2)

Sterile small test tubes (6 x 30 mm)



  1. Prepare a plant-tissue extract by grinding the tissue in an appropriate solvent.
  2. Obtain two small culture tubes. Using a Pasteur pipette fill each tube about two-thirds full with culture media. Run the media down the side of the tube being filled to avoid making air bubbles. You may need a third tube with culture media plus solvent as a control.
  3. Add a plant extract to one of the tubes. You will have to experiment to determine the appropriate dilution.
  4. Using a dissecting microscope, catch a protozoan (e.g., Paramecium, Blepharisma, or Amoeba and place it in one of the tubes. Repeat the procedure to inoculate the second tube.
  5. Examine each tube under dissecting microscope or low-power of a compound microscope to locate each protist. Record this initial count (of 1) at time 0.
  6. Examine the cultures at regular intervals over the next week and record the number of cells in each. Try to count the cells at least once each day (Monday through Friday).
  7. Graph your data.

Growth Curve





The effect of a cyanobacterial extract on the growth of Paramecium.