Who doesn’t love an easy experiment?! We recently lined up a slew of experiments with petri dishes and our home grown bacteria from our bodies. It’s especially fun to do this if you’re recovering from an infection or have just been gardening (or making mud pies) because you’ll get some really interesting results a few days later…
Ok first, where to get petri dishes? You don’t have to work in a lab to get them. Just check out amazon for “petri dishes” and you’ll find kits with multiple dishes in one. Some already have agar, and some come with mixing kits. We got ours the next day, so this is a great idea if you’re running out of things to do right now. Don’t be worried about mixing and pouring agar– it’s super easy, but also not necessary to do this step yourself. If you want to just skip right to the fun, get the pre-poured petri dishes!
There are a ton of good ideas online about what you can swab. While I have plans of testing surface areas in the future, we had enough fun swabbing our hands, noses, cheeks, ears, and fingernails. We did some petri dishes with half germs, half toothpaste or antibiotics. See below for that lineup.
Our results after one day were just faint dots, but after three days we could see some very interesting colonies forming, and by five days it was actually pretty disgusting (aka fun)! We looked up the different colonies on wikipedia, and compared ours to various science experiments posted by labs found online.
Our petri dish lineup:
1. Accidental full hand swipe of three year old’s hand after playing outside in the dirt. (Because he ran in and opened a clean petri dish and swiped it before I could stop him). RESULT: colonies of staph and mold. Actually his was the most interesting result, and it encouraged him to immediately go wash his hands when we noticed these dangerous colonies forming (a fantastic unexpected side effect).
2 and 3. Baby’s nose and inside mouth with triple antibiotic ointment on one side of one dish, and nothing in the other. (Side note: baby had just been to the urgent care for croup and an ear infection, so we knew he had some unique bacteria to find, and did we!) RESULT: a large streptococcus colony in dish without antibiotics. A small strep colony in other dish with nothing on antibiotics side.
4 and 5. Five year old’s mouth, with children’s non-flouride toothpaste on one side. Mom’s mouth with adult non-flouride toothpaste on one side. Different toothpaste brands. RESULT for both: formation of basic white bacteria colonies with reduction around toothpaste.
If you do petri dish experiments, please comment about it! I would love to hear what other people do.