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Care Guide: Bacteria

Living Care Information


Quick Start Information

  • When your order arrives, open the shipping box immediately and remove the culture.

  • For tube cultures, visually inspect the culture to ensure that tubes are intact with secure caps.

  • For plate cultures, check to make sure plates are free of cracks and taped along the edges.

  • For MicroKwik Culture® freeze-dried cells, check that the vial is securely capped and that the tube of reactivation medium is intact.

  • Tube cultures should remain capped until they are ready to be used.

  • Plate cultures are taped to keep the lids on the plates. Leave the tape in place until just before use. This will slow the loss of moisture from the agar and lessen the chance of contamination.

About the Organism

  • Fossil bacteria are found in rocks that are 3.5 billion years old, making them the oldest known life.
  • Bacteria are prokaryotes—they lack a membrane-enclosed nucleus.
  • They are found everywhere, from high in the earth’s atmosphere to at least 2 miles underground.
  • With an estimated population of 5 million trillion trillion, bacteria outnumber all other life on earth.
  • Domain: Eubacteria
  • Kingdom: Bacteria


Our tube and plate cultures have already been incubated and are ready to use when received. MicroKwik cultures (freeze-dried) must be reactivated before use. To reactivate, follow the instructions included with your culture.

To prevent contaminating yourself and work surfaces when handling a bacterial culture, you should follow a simple set of procedures collectively referred to as sterile technique. See our manual Techniques for Studying Bacteria and Fungi for more information on proper handling methods.

Before you start working with a bacterial culture, wash and dry your hands and wipe down all work surfaces with disinfectant. Most labs have regulations regarding which PPE (personal protective equipment) you must wear and which protocols you must follow. It is your responsibility to know and follow all requirements. At the end of a work session, return all cultures to storage areas, wipe down all work surfaces with detergent, and wash and dry your hands before leaving the lab.

Never work with a bacterial culture in areas where food is stored, prepared, or consumed.


No housing information applies for this organism.


No feeding information applies for this organism.

Maintaining and culturing

Our tube and plate cultures are incubated and grown to maturity before shipment. No additional incubation is needed. Most can be held at room temperature for up to 3 weeks before they need to be transferred to fresh media.

A MicroKwik Culture can be held at room temperature for up to 2 months before activation or 6 to 8 months if refrigerated.

Eventually the bacteria will exhaust the nutrients in the media and require transfer to fresh media if you wish to keep the culture thriving. Our catalog and online descriptions list the media we use for the culture and the optimal incubation temperature. In most cases, you will get the best results if you use the same media that we use. If you do not have an incubator, many common bacteria (Bacillus cereus, Escherichia coli, Serratia marcescens, etc.) will grow at normal room temperatures of 20 to 22° C (68 to 73° F), but they may grow a bit slower. Instead of getting heavy growth in 24 hours, it may take 48 hours, depending on the bacterium.

Note: Rhodospirillum rubrum and Vibrio fischeri have very specific requirements. For successful maintenance and culturing, please see their specific care guides.


You may be subject to local regulations that specify certain disposal methods. If so, you must strictly adhere to those regulations.

Otherwise, the preferred way to dispose of a bacterial culture is to place it in an autoclavable bag and run it through the sterilizing cycle of an autoclave. If you don’t have an autoclave and are working with a BSL-1 organism (see Biosafety section below), make a solution of 1 part household chlorine bleach to 9 parts water. Pour this into a plastic dishpan or similar container. Wear disposable gloves, splash-proof goggles, and a face mask or face shield. Place all culture tubes, plates, and other materials that have been in contact with bacteria into the bleach solution. Once the tubes and plates are submerged, remove the caps and lids. Allow everything to soak submerged overnight.

After 12 to 24 hours, pour the bleach down a laundry drain or toilet and follow with a flush of 1 to 3 gallons of water. Put all items in a plastic bag and seal it. Drop that bag into a second one and seal it. Dispose of the bags in the trash. Note: This disposal method must never be used with a BSL-2 organism, and certain local regulations may prohibit this method of disposal.


In the United States, the Centers for Disease Control and Prevention (CDC) sets standards for the safe handling of microorganisms according to their biosafety level (BSL). There are 4 levels, with BSL-1 being the lowest risk microorganisms and BSL-4 being the highest risk.

The CDC standards for working with BSL-1 microorganisms include the following:

We ship BSL-1 and BSL-2 cultures. Our catalog and online listings identify BSL-2 bacterial cultures as pathogens. They are only available as MicroKwik Culture freeze-dried cells, and we can ship them only to colleges and universities. Cultures not identified in our listings as pathogens are BSL-1.

  • Follow all standard microbiological practices
  • Work can be performed on an open lab bench or table
  • Wear personal protective equipment (PPE)—lab coats, gloves, and eye protection—as needed
  • A sink for hand washing
  • Doors that separate the lab room from the rest of the facility

When working with BLS-2 microorganisms the CDC recommends all the above, plus the following:

  • Restricted access to the lab room while cultures are being used
  • PPE should include face shields as needed
  • All procedures that can produce a splash or an aerosol must be performed within a biological safety cabinet
  • A sink for hand washing
  • An autoclave or other method of decontamination for proper disposal
  • Self-closing doors that separate the lab room from the rest of the facility
  • An eyewash station

For more details on CDC criteria for handling microorganisms, see the organization’s Laboratory Biosafety Level Criteria.



Which agar should I use for my bacterial cultures?

In our print and online catalogs, the product descriptions for our bacterial cultures include the type of nutrient medium that we use for each culture. You can also consult our Bacteria and Media Reference Guide. This information also appears on the label affixed to the culture. A wide range of bacteria will grow on Nutrient Agar and Tryptic Soy Agar.

Can I pour my own plates if I don’t have an autoclave?

Yes. See our Nutrient Agar Bottle and other prepared media bottles. A bottle containing 125 mL of medium will pour 5 standard 100 × 15-mm plates. Watch our video on melting and pouring agar plates for a demonstration of the technique.

Should I order a tube, plate, or MicroKwik Culture?

Tube cultures are best for stock. A tube culture is often streaked on a plate and incubated before lab use. Order a plate culture for convenience and immediate use. You can receive a plate culture and use it in a lab on the same day. A MicroKwik Culture is best used for long-term storage and to receive a culture of a pathogen. It can be held at room temperature for up to 2 months before being activated or for 6 to 8 months refrigerated.

Which cultures should I order for antibiotic testing?

Gram-positive and Gram-negative bacteria often give different results when tested against the same antibiotic. For that reason, we recommend testing against Bacillus cereus, which is Gram-positive, and Escherichia coli, which is Gram-negative. We recommend broth cultures because this makes it easier to spread the culture over the surface of an agar plate. See our Carolina BioKits®: Antibiotic Sensitivity for more information.

You recommend holding a culture at room temperature, but the recommended temperature for Escherichia coli is listed in your catalog as 37° C. Why is that?

This is because 37° C is the incubation temperature, or the temperature needed for maximum culture growth. The culture is mature when we ship it and does not need further incubation. Maintaining the culture at room temperature allows you to hold it longer before use.

I need to incubate Micrococcus luteus at 25° C and Staphylococcus epidermidis at 37° C, but I only have one incubator. Which temperature do I use?

Incubate at the lower temperature. Staphylococcus epidermidis will grow at 25° C, but if you incubate Micrococcus luteus at the higher temperature, it may damage the culture.

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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