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How to Mold Cultures in Gelatin

Cultures are often molded in the gelatin of a petri dish to grow. To do this, a culture broth must be poured over the soft gelatin for the gelatin to absorb the culture. The gelatin acts as food for the culture to grow because it is high in protein. Agar agar is typically used as a growth medium gel in petri dishes, however gelatin is higher in protein which allows some cultures to flourish more than it would in agar agar.

Things You'll Need

Glass jar or beaker
Distilled water
Digital gram scale
Hot plate
Plastic cup
Food thermometer
Culture broth
Petri dish

Instructions

- 1
  Place the glass jar or beaker on the gram scale and tare the scale to bring the weight to zero by pressing the "tare" button.
- 2
  Pour 1 cup of cold distilled water in the jar or beaker. Tare the scale with the jar or beaker still on the scale, by pressing the "tare" button until the weight reads zero again.
- 3
  Sprinkle gelatin into the water until the scale reads 1 ounce. This should equal 1 packet of pre-measured gelatin from a grocery store. Swirl the jar or beaker to combine the water and gelatin and allow the gelatin to bloom.
- 4
  Place the jar or beaker on the hot plate and turn the hot plate to medium-high temperature. Place the thermometer in the liquid and bring it to 160 degrees Fahrenheit, then remove it from the heat.
- 5
  Place the plastic cup on the scale and press the "tare" button until the scale reads zero. Pour 10 grams of culture broth in the cup. Pour the culture broth into the jar or beaker and swirl it around about 10 times or until thoroughly blended.
- 6
  Pour the gelatin mixture in the petri dish until it reaches 2 mm deep. Place the petri dish in a refrigerator to set for five hours. Allow the culture to grow at 40 degrees Fahrenheit for 24 hours or until colonies form on the gelatin surface.

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