Science Buddies: "Ask an Expert"

OK, so for my project I am testing which cleaning method kills the most bacteria on a kitchen counter. I will be growing bacteria. I need information on how to keep myself from transferring more bacteria on the counter and swab. In other words, how do I only test the bacteria on the counter, and not the stuff I put on there. Please respond~~~

Hi dancing_star_14,

I don't exactly know what you mean by only "test[ing] the bacteria on the counter, and not the stuff [you] put on there." Do you mean that when transferring bacteria from the swab onto your plate, you are afraid of foreign bacteria contamination? If so, this is really inevitable. During your trials, employ all aseptic techniques: wash your hands thoroughly and frequently, clean all equipment before use, don't talk when doing your experiment. When lifting the petri dish cover, open away from the mouth. These things can prevent foreign bacteria from growing on your plates or sticking onto your swab.

Also, testing cleaning methods on a kitchen counter top can be tricky. When you inoculate your dish with the bacteria from the counter, and place disks soaked in different solutions designed to kill bacteria, you might be looking at many different species of bacteria. If you want to control this, test a cleaning solution/method on only one species. This project is extremely interesting though. My Science Buddy, sunn, did something very similar to yours. Sunn testing bacterial contamination of chicken broth. Because four to five different types of bacteria grow in the broth, it was hard for Sunn to identify what species the broth killed, because some colonies were very close to the disks, and some weren't.

If you want some ideas on how to do your project, visit the Mouth Microbes thread on this forum. When the dialogue between sunn and I begins, you will find some useful information on how to conduct your experiment if needed.

I hope this helps.

Sincerely,
Sareena

Thanks for the help!¡!¡!