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Living Organism Care Guide: Tetrahymena

Living Care Information

Tetrahymena
pyriformis

Quick Start Information

  • Open the shipping container. Remove and inspect the tubes of Tetrahymena.

  • Aerate the culture to help replace the oxygen depleted during shipping. To aerate, turn the culture tube over 4 times. Do not loosen the cap.

  • Keep the culture tubes at room temperature (about 21 °C, or 70 °F) and out of direct sunlight.

About the Organism

  • Tetrahymena is used in research as a unicellular eukaryotic model organism to study environmental toxicity, pharmacology and cellular biology and processes.
  • Cell size, shape, and structure: Typical cells are 60-100µ long, banana or pear-shaped and covered with 17-23 cilia.
  • Tetrahymena are important in aging research because individual cells can divide indefinitely. Telomeres and telomerase were first discovered in Tetrahymena.
  • Tetrahymena have been isolated from sources all over the world including lakes, streams, rivers, thermal springs, soil and even the body cavities of aquatic insects.
  • Tetrahymena were first described by Anton van Leeuwenhoek.
  • Domain: Eukarya
  • Kingdom: Alveolata
  • Phylum: Ciliophora
  • Class: Oligohymenophorea
  • Order: Hymenostomatida
  • Family: Tetrahymenidae
  • Genus: Tetrahymena
  • Species: pyriformis

Preparation

If you plan to culture your Tetrahymena, you will need a supply of fresh Tetrahymena medium on hand. Carolina’s Tetrahymena cultures are axenic and therefore sterile technique must be employed to maintain the stock culture as a pure culture. Subcultures should be made for student experiments. Students do not need to use aseptic technique when working with their cultures unless their experiments require the use of axenic cultures.

Housing

Tetrahymena cultures should be incubated at room temperature (20 to 22° C). If necessary, you may lower the incubation temperature, although population growth will slow down. It is also safe to incubate at higher temperatures, in which case the population growth rate will increase. Do not exceed 29° C for stock culture incubation. Tetrahymena can be maintained in tubes or flasks, but growth is better in flasks where oxygen diffusion is greater. No attention should be given to lighting or photoperiod (light and dark cycles).

Feeding

Tetrahymena medium provides all necessary nutrients for culture maintenance. The proteose peptone medium can be made using the following formulation:

Adjust the medium to a pH of 7.2 before autoclaving. Place 25 mL each into 20 individual, 125 mL Erlenmeyer flasks (or another suitable container). Plug the tops of the flasks with cotton or a foam plug. Cover the tops with aluminum foil. Autoclave for 20 minutes at slow exhaust (liquid cycle) to eliminate the risk of boil over.

For a faster growth rate, a 2% proteose peptone medium can be made using the following formulation:

Dispense and sterilize as described above. Store refrigerated for up to 2 months.

Maintaining and culturing

Stock tubes should be transferred to fresh media every week using aseptic technique. Select a fresh tube of medium by agitating to see if any visible cloudiness is seen. If the medium in the tubs appears clear, it is fine to use. If cloudiness or turbidity is seen then there is a contaminant in the medium and the tube should be discarded. Transfers should be made by inoculating 25 mL of medium with 1 mL of actively growing Tetrahymena cultures. Pipet the top layer of medium to collect your inoculum, as this area contains the highest density of actively dividing cells.

Disposal

When you are finished with your cultures, they can be added to an aquarium where they will serve as food for small fish. You can also dispose of them by pouring them down a sink, followed by a flush of a gallon of water. The chlorine in most tap water will kill protists. If your water supply comes from a well, your water may not be chlorinated. If that is the case, add 1 mL (20 drops) of household bleach or alcohol to the culture. Allow the jar to stand for 15 minutes before disposal.

Biosafety

None of the protists supplied by Carolina are pathogenic or parasitic. Our technicians have worked with these organisms for many decades without problems. We recommend that you wash and dry your hands after working with any microorganism.

Video

FAQs

How long can I keep my cultures before using them?

It is always best to use protozoan cultures within a few days of receipt. With simple care, most will last for 5–7 days. Tetrahymena stock cultures should be subcultured once per week. If in doubt, examine your culture under a stereomicroscope to see if it is still useable.

My cultures arrived on a Friday. Can I keep them over the weekend and use them for class on Monday?

Yes. Remove the cultures from their shipping container, and care for them as directed above. Do not leave your cultures in the unopened shipping container. Heterotrophic forms are shipped with enough food in their jar to maintain the culture for an extended period. You may even find that the cultures improve when left over the weekend because they have had time to recover from the shipping process.

My students are not finding any Tetrahymena. What should I do?

Tetrahymena typically congregate in the top layer of a culture as this is where oxygen concentration is highest.

We used Protoslo® quieting solution, but now all the Tetrahymena are at the edge of the coverslip and some have even been squeezed out from under the coverslip. What can I do?

If the Protoslo® solution and culture water are not thoroughly mixed, the thicker solution will displace the water and protozoa when the coverslip is added. If this occurs, clean the slide and start over. Be sure to thoroughly mix the Protoslo® solution and culture water before adding the coverslip to the slide.

Need help?

We want you to have a good experience. Orders and replacements: 800.334.5551, then select Customer Service. Technical support and questions: caresheets@carolina.com

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