How to Culture Bacteria

Culturing bacteria can be as simple as setting a piece of bread in a warm moist place and allowing penicillin and other bacteria to take root. It can also be so complex as to require special incubators that are set to specific temperatures.But if you really want to culture bacteria at home--to assess cleaning methods or products, for example--then there is a simple and scientific method to grow bacteria cultures with little or no additional contamination.The process involves the purchase of petri dishes, agar and sterile cotton swabs. If there is a scientific dealer near your home, or even a large hobby center, you may be able to purchase all equipment locally. If not, everything is readily available online.

Things You'll Need

• Agar
• Cooking thermometer
• Small cooking pot
• Petri dishes
• Sterile cotton swabs
• Warm dark cupboard
• Book on bacteria cultures

Instructions

1. Mix the agar according to the manufacturer's instructions. Agar is a bit like Jell-o and the ingredients will need to be heated to precise temperatures. Make certain that you have a clean cooking thermometer handy.

2. Open a petri dish and pour just enough agar into the dish to cover the bottom completely. Put the lid back on immediately and set the dish aside until the agar firms. Fill each dish the same way, never leaving the top of the dish off any longer than absolutely necessary. Once the agar hardens you may store the dishes in the refrigerator upside down to avoid the possibility of any airborne bacteria getting into the dishes.

3. Remove the petri dishes from the refrigerator only when you are ready to use them. Open your sterile cotton swab package and rub the cotton swab on a surface you wish to test for bacteria, such as a countertop. Open a petri dish and rub your swab gently across the surface of the agar in an "S" pattern. Close the lid on the petri dish.

4. Set the dish in a warm dark cupboard for three to four days.

5. Remove the dish from the cupboard. There is no need to open the dish. Observe the bacteria colonies through the top of the dish. Record their color, shape and anything else distinguishing. Look in a bacteria book or on the Internet for illustrations that match the bacteria you have cultured.

6. Destroy your cultured bacteria once you have identified it. Pour 1 tbsp. of bleach into the petri dish and then seal the dish closed with packing tape, put the dish in a baggie, seal it and throw away.

Tips & Warnings

• You can culture bacteria from almost any surface. Take your time identifying the bacteria that you have cultured and learn as much about it as you can.

• Do not open a petri dish with cultured bacteria until you know what type of bacteria you have and what its characteristics are. Exercise caution.

Resources

• Buy your supplies here
• Excellent book for identifying bacteria