Science Buddies: "Ask an Expert"

Hello. My name is George, and I'm currently in the 9th grade.

I have decided to do my science fair on growing bacteria cultures in agar plates from random swabbed samples (e.g my kitchen counter, or door knob). One problem I have is that I don't know what and how i will measure for my qualitative data. Do you think i should compare the amount of bacteria from different samples? And if so, how will I do that? I've also told conflicting things about whether I need an incubator or not to grow my bacteria. I do not have an incubator, and my school does not either. Do I need to incubate my cultures?

FYI, I have no real background on microbiology, and am just learning about animal and plant cells in biology.

Hi George and welcome to Scibuddies!
Bacteria make great subjects for science projects because they are everywhere and they are easy to grow. You don't need an incubator, but the Petri dishes should be kept where it is reasonably warm--no lower than 75F (24C).

Bacteria are not the only microsocopic life form that share the space with us. The fungi, mold and mushrooms, reproduce by making spores (sort of like seeds) and these can grow on agar too. Bacteria make roundish colonies, usually white, while fungi can make fuzzy, fibrous growths called hyphae.

Just remember that while most bacteria are harmless or even good for you, there are some bad ones like Salmonella and Staphylococcus that can cause disease ore even be fatal in humans. So, when doing any experiments with bacteria, always where safety glasses and disposable nitrile gloves. Also, once you have swabbed the agar with the samples and labeled the bottom of the plate so you know which part has which sample, attach the lid to the base with tape and DON'T open it again! This is important because the bacteria and fungi that can grow on nutrient agar can make you very sick and you don't want that! At the end of the experiment, get a 2 gallon plastic pail and fill it about half full with a 10% solution of Clorox bleach: 1 1/2 cups [12 oz] of Clorox plus 3 1/2 quarts of water. Put the still-sealed Petri dishes in the solution and let them soak overnight. Then you can drain out the liquid and put the plates in regular trash for disposal.

Ok, now for the education part--
You said you don't know anything about microbiology--well, it's high time you learned. You can start with SCibuddies tutorials on doing experiments with bacteria: https://www.sciencebuddies.org/science- ... egulations

https://www.sciencebuddies.org/science- ... petri-dish

https://www.sciencebuddies.org/science- ... robes-agar

For more fun, watch these Youtube videos that show you how to work correctly with bacteria in the lab:
https://www.youtube.com/watch?v=yY8STATjZ6U
https://www.youtube.com/watch?v=u84bTjqrt7k
https://www.youtube.com/watch?v=nKFzlAuEyII
https://www.youtube.com/watch?v=1xuEowtB7qg

There are lots more good videos out there, so happy hunting!

When you have more questions, post again and we will try to help.

Sybee