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You can run, but you can't hide when it comes to bacteria. They can be found everywhere on earth, from Antarctica to the inside of your intestines! Some are good, aiding digestion and giving us tasty food like cheeses and yogurt. Many are harmful, causing serious diseases; these are called pathogenic bacteria. Learn more about what bacteria are, where they live, and how they can help or harm us in our Bacteria: Tiny But Tough article.
You have millions of bacteria living on your skin. While some types are harmless, bacteria are a major source of illness. They spread easily every time you touch something — you leave them and pick them up on doorknobs, telephones, and more. Touching your face (especially eyes, nose, and mouth) with your hands can allow bacteria to get inside you and make you sick. One of the best ways to prevent the spread of illness is just to wash your hands well in soap and water. It seems so simple, but it really does work! With this project, you can experiment to see which hand soaps are most effective in getting rid of bacteria.
While most environmental bacteria are not harmful to healthy individuals, once concentrated in colonies, they can be hazardous. To minimize risk, wear disposable gloves while handling bacteria, and thoroughly wash your hands before and after. Never eat or drink during bacteria studies, nor inhale or ingest growing cultures. Work in a draft-free room and reduce airflow as much as possible. Keep petri dishes with cultured mediums closed—preferably taped shut—unless sampling or disinfecting. Even then, remove the petri dish only enough to insert your implement or cover medium with bleach or 70% isopropyl alcohol. When finished experimenting, seal dishes in a plastic bag and dispose. Cover accidental breaks or spills with bleach or alcohol for 10 minutes, then carefully sweep up, seal in a plastic bag, and discard.
>> Watch our video to learn how to set up a bacteria experiment and see bacteria colonies grown from a kitchen sink!
Part 1: Preparing culture dishes
Part 2: Hand soap experiment
The rate of bacteria growth in your dishes will depend on temperature and other factors. Check your cultures after a couple of days, but you'll probably want to wait 5-7 days before recording your data. You will see multiple round dots of growth; these are bacteria colonies. There may be several types of bacteria growing in the dishes. Different types of colonies will have different colors and textures.
For each soap test, count and record the number of bacteria colonies in each dish. To see how effective each soap was, divide the number of colonies in the test dish by the number of colonies in the control dish, then subtract the result from 1 and write the answer as a percentage. For example, if your control dish had 100 colonies and your soap test dish had 30, the soap eliminated 70% of the bacteria: 1 — (30 ÷ 100) = .7 = 70%
According to your results, which type of soap was the most effective at eliminating bacteria? Does "antibacterial" soap really work better than regular soap? How well did washing hands in water without soap work? What further tests could you do to determine which soaps and hand washing methods are most effective at eliminating bacteria?
|A Customer Favorite:
Bacteria Experiment Kit
Explore the fascinating diversity of bacteria in your own environment! With this kit you can experiment with bacteria in the air, on surfaces, and on your hands. You can also test the antibacterial effects of common household cleaners. This experiment/study kit comes with instructions and all the supplies you need for growing 20 bacteria cultures
Find fascinating news, images, and video about bacteria and other microorganisms at the MicrobeWorld site.
Learn about the importance of handwashing in this video from the Center for Disease Control
Check out amazing pictures of microbes in this photo gallery.
- Bacteria that love the heat are called thermophiles, and can survive in temperatures as hot as 284° F! Cold-loving bacteria, called psychrofiles, can live in permanently ice-covered lakes in Antarctica.
- A single bacterium is far too small to see without the help of a microscope...except for the Thiomargarita namibiensis ('sulfur pearl of Namibia') which is as big as a period at the end of a sentence!