Grow bacterial colonies and bacterial reactions

Bacteria growth is usually performed under temperature conditions. Petri plates are filled with with agar, which feeds bacteria that are inoculated on the surface. Under the proper conditions (usually 37 degrees Celsius), the bacteria will consume the agar as food and grow into colonies called colony forming units (CFU’s). The Revolutionary Science Incufridge is a chilling incubator that can be used as a standard bacterial incubator for growing bacterial colonies on petri plates.


Counting colonies quantifies the affinity the colonies have for the agar, but also is indicative of the amount of bacteria. Colonies may be counted by hand or by using the Revolutionary Science IncuCount, an automated cell counter. Aseptic techniques should be employed. Petri plates should be properly disposed of after they are no longer needed, by sterilizing in an autoclave, like the Saniclave 50.

  1. Suspend 28 grams of nutrient agar powder in 1 liter of distilled water. Use a flask at least double the size of the volume to avoid boiling over.
  2. Gently swirl this mixture while stirring to fully dissolve all components.
  3. Cover the flask with aluminum foil or a loose fitting cap. Using the Saniclave, sterilize the dissolved mixture at 121C for 15 or 30 minutes. Make sure that you sterilize it using a liquid load.
  4. Once the nutrient agar has been autoclaved, allow it to cool for 10 minutes, but not solidify. Gently swirl to confirm that the agar solution is smooth and not lumpy.
  5. Pour nutrient agar into each plate and leave plates on the sterile surface until the agar has solidified.
  6. Each batch will make 40 plates (25mL/plate). If storing is necessary, store the plates in a refrigerator, upside down.
  7. To inoculate the plates, use a sterile cotton swab, inoculation loop or other method. Use aseptic techniques! Wear latex or latex-free gloves.
  8. Incubate plates upside down in an Incufridge, set at 37C or another desired temperature until colonies are visible. Colonies can be counted using the IncuCount.
  9. Dispose of the plates in an aseptic manner. Place petri plates, cotton swabs or inoculation loops into an autoclave bag and sterilize in a Saniclave for 30 minutes.

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