Insects and the germs they carry
The materials required for this science fair project:
- 4 petri dishes prepared with agar
- 4 plastic containers
- An ant
- A cockroach
- A fly
- A beetle
- Ensure that all of these insects are caught from the same general location - ie: if you decide to catch these in your garden, let it be only from your garden. Don't catch some of the insects in your garden, and the rest from your neighbors'.
- A ruler
- A stopwatch
- A clean pair of tweezers
- 1 marker pen
1. For this science fair project, the independent variable is the type of insect used – the ant, cockroach, fly or beetle. The dependent variable is the size of bacteria colony that grows in each petri dish. This is determined by measuring the approximate diameter of the colony with a ruler. The constants (control variables) are the room temperature, the amount of sunlight, the garden from which the insects are obtained, and the agar preparation.
2. The 4 petri dishes are filled with agar and stored in a refrigerator. The petri dishes are brought to room temperature before the start of the experiment. They are taken out of the refrigerator and allowed to warm up to room temperature. The 4 petri dishes are labeled “ant”, “cockroach”, “fly” and “beetle”.
3. An ant, a cockroach, a fly and a beetle are caught with the tweezers and kept in separate plastic containers. Once the petri dishes have attained room temperature, the insects are released onto the respective petri dishes and the plastic containers are closed with their covers. The insects are allowed to crawl all over the agar for 1 minute. After 1 minute is over, the cover of the petri dish is removed and the insects are released.
4. The petri dishes are then sealed with their covers and kept in a cool shaded place to allow the bacteria to grow for the next 5 days. The diameter of the bacteria colony growth is measured everyday for 5 days and the measurements are recorded in the below table.
Always follow laboratory safety guidelines and always practice sterile technique when handling microbes. Never have any food or drink at your workstation and always thoroughly wash your hands with disinfectant soap or alcohol before leaving your workstation. Always dispose of used material in a biohazard bag. If none are available, the bacteria should be destroyed with bleach before being disposed of. Knives should be handled under adult supervision.