Frequently Asked Questions about Living Cultures

Many of you have questions about ordering and caring for cultures of protozoa, protists, and bacteria. We’ve gathered the most frequently asked questions here, along with the answers, as a quick reference. While it should answer most common questions and concerns, organism-specific information can be found in the instructions shipped with the culture and by searching our Carolina™ Care Sheets.

Protozoa and protists

“When should I order protozoa?”

A living culture should be ordered a couple of days before use. We recommend receiving it on a Tuesday, Wednesday, or Thursday and using it the same week if at all possible. Try to arrange delivery at a time when you can personally receive the package and examine its contents. Inform your institution’s receiving department or office personnel to contact you immediately once it arrives. If you can’t get to the package right away, have someone place it in a climate-controlled area—NOT in a refrigerator—until you can attend to it.

“How long will my protozoa survive in the shipping container?”

Protozoa and algae cultures will survive for about one week in the shipping container. When you receive your protozoa culture, remove the lid and gently aerate the culture using a clean pipet. Allow the culture to settle after aeration and then use a stereomicroscope to check for activity. Replace the lid and set the culture in an area away from direct sunlight or extreme temperature changes.

• For Euglena, make sure the cap is loose and place the container in a well-lit area, but not in direct sunlight.
• As a rule of thumb, don’t place a protozoa, algae, or bacteria culture in the refrigerator. Exceptions are particular cultures of fungus that should be refrigerated to slow their growth, and when the instructions specify that refrigeration is an acceptable means of storage.

“How can I extend the life of my protozoa if I don’t want to subculture them?”

We recommend using the culture within 5 days of receipt. However, the life of your protozoa can be extended by feeding and by replenishing the culture water. For organisms that feed on bacteria, a single grain of precooked rice can be added to the culture container. Some organisms require algae or other food sources; be certain to research what food the organism requires prior to ordering. To replenish the culture water, allow the organisms to settle to the bottom of the jar, and then gently pour off about a quarter of the water and replace it with fresh springwater. Never use tap or distilled water.

“Some of the water from the culture container spilled (or evaporated) and I want to add more water. Can I just add some tap water? What kind of water is best?”

Never add tap water to a culture. It contains chlorine and in some cases chloramines that are toxic to protozoa, algae, and other living organisms such as fish and tadpoles. Use room temperature springwater instead. We recommend Carolina™ Springwater, which we use to grow many of our organisms. If this is not an option, you can purchase springwater from your local grocery store. Be sure to carefully read the label to ensure there are no additional additives for taste, and that the source is not a municipal water supply. The label should state that the water came from a “natural springwater” source.

“What types of microscopes can be used to view live organisms?”

For protozoa and algae use a compound microscope for close, detailed viewing. To observe swimming and interactions with other organisms within the culture, use a stereomicroscope. Use a compound microscope with an oil-immersion objective to view bacteria and fungus.

“What are the ingredients of Alga-Gro® media?”

Alga-Gro® media are proprietary mixtures; therefore, we do not disclose specific information about the amounts or types of ingredients they contain.

“What is the enzyme concentration?”

Enzymes do not have a specified concentration like chemicals do (e.g., 3% hydrogen peroxide) they have an activity level. The activity level varies with each enzyme. If you need to know the activity level of a particular enzyme, call our Customer Service Department (800.334.5551); and ask the representative to connect you with a technician in our Cultures Department  for this information.

“What types of organisms will I see in the Carolina™ Pond Mystery Mix or the Hay Infusion Kit?”

The number and types of organisms vary from culture to culture. Remember to always use springwater when setting up a culture; do not use tap or distilled water. It takes time for organisms to appear and become abundant, so allow at least one to 2 weeks for organisms to grow and emerge.

How to maintain algae in your classroom:

Do

• Keep at room temperature (22° C or 72° F)
• Loosen caps on tubes or jars and keep upright
• Use sterile culture vessels and pipets
• Use within 5 days of receipt or set up subcultures after 5 days to maintain longer
• Provide correct light intensity (indirect sunlight or artificial light)
• Read the Carolina™ Culturing Algae Manual—included with each order of algae and available separately

Don’t

• Put in the refrigerator
• Put in direct sunlight
• Wash glassware in detergent
• Keep above 30° C (86° F)—lethal to algae

Bacteria

Do I need to place my bacteria cultures in an incubator when I receive them?” The short answer is no, not every bacteria culture needs to be incubated. The temperature listed on the label is the temperature at which the culture would optimally grow if you were growing it in subculture. Most bacteria store well at room temperature and will remain viable for 3 to 4 weeks. Of course, there’s always the exception! Spirillum volutans needs to be kept at 30° C.

“Can my students get cancer from using Agrobacterium tumefaciens in the Carolina™ Plant Cancer Study Kit?”

No, they can’t. The cancer seen in susceptible plants is the result of a bacterial infection that is specific to plants, not humans. Susceptible plants include roses, grapes, apples, cherries, pecans, sunflowers, tobacco, beets, turnips, and tomatoes.

“Do I have to use a fresh, 24-hour culture of bacteria to perform a Gram stain?” Yes, you do. As the culture ages, the bacterial cell walls become more permeable to the crystal violet-iodine complex, making the cells easily decolorized. This will cause Gram-positive bacteria to stain negative.