Microbial ecology without the microbes.

Today at daycare there was the dreaded sign warning parents that Streptococcus pyogenes (the bacteria that causes strep throat) had been found on the premises. This got me thinking about bacteria cultures…and jello.

Bacteria can be grown in petri dishes that have been prepared with a layer of agar and growth medium. Such cultures are used to determine the type of organism and its abundance in a sample. Consequently, this method is frequently used to help doctors determine the cause of many infectious diseases.

It’s also a key step in many synthetic biology and biotech experiments.

If you’re looking for a noncontagious – and maybe even delicious – way to introduce students to microbial cultures check out the easy activity below. This activity also works as a great precursor to a transformation experiment such as our Rainbow Transformation Kit as it allows students to practice essential microbial biology techniques beforehand.

For this activity you will need a pack of Jell-O®, a small tube of icing or similarly viscous liquid, water, a beaker and ten additional petri plates (or the lids from any wide mouth jar or container). You will also need ten toothpicks or inoculating loops and ten small test tubes.

  1. Make 10 Jell-O® practice petri plates.
  • In a large breaker mix Jell-O® powder and water according to the package directions.
  • Quickly pour the Jell-O® into petri plates, filling about half way.
  • Allow plates to solidify in the fridge for 30-60 minutes.
  • Add 10 dots using whatever liquid you choose. Dots may be larger than true bacterial colonies.
  1. Give each student group a plate, a toothpick or loop, and a microcentrifuge tube containing water.
  2. Challenge students to transfer all the “bacteria” colonies into the tube without breaking the Jell-O®.Screen Shot 2019-07-16 at 8.42.22 AM

Students can also practice preparing a plate by mixing the frosting and water and then spreading the mixture back onto the plate with their loop. They can even practice streaking of plate. However, for this activity we recommend switching the solutions to something like balsamic salad dressing. While this doesn’t exactly compliment the taste of jello, it does let the students see the decline in density from streak to streak because of its color and viscosity.

Happy plating.




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