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Molecular Biology Science Fair Project

Bacteria in Your Toothbrush

Bacteria in Your Toothbrush | Science Fair Projects | STEM Projects
In this experiment, you will test the bacteria growth in three different toothbrushes, each with a different treatment. You will measure the size of the bacteria colony growth over five days and compare the results.


The hypothesis is that the toothbrush kept in Listerine solution will have the least bacteria.

Method & Materials

You will prepare three agar petri dishes, disinfect three swabs, and label three toothbrushes. You will give each toothbrush a different treatment for five days, then take a sample from each toothbrush and roll it in the petri dishes. Finally, you will measure the size of the bacteria colony growth in each petri dish over five days.
You will need three agar petri dishes, three disinfected swabs, one bottle of disinfected water, three toothbrushes, one bottle of Listerine, one tube of toothpaste, and one marker pen.


The results showed that the petri dish with the toothbrush that was used with only water had the quickest bacteria growth. The petri dish with the toothbrush that was kept in Listerine had the least amount of bacteria growth.

Why do this project?

This science project is interesting because it shows how different treatments can affect the amount of bacteria growth in a toothbrush.

Also Consider

To improve the reliability and accuracy of the results, a larger sample of participants should be used. This science project can also be repeated, this time taking a swab sample from the mouth after gargling with water, mouthwash, and Listerine and comparing the bacteria content.

Full project details

You can find additional information and details for this science fair project here. Have fun exploring!

Related videos

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