A Cultured Science Experiment: Grow Your Own Bacteria

My parents bought the kids an awesome microscope for Christmas and they lucked out by getting a superb demonstration from both of their scientist grandparents last weekend. As we were reading through the accompanying book and talking about viewing different organisms, I remembered that the kids and I spent an afternoon last year culturing bacteria and I completely forgot to share the experiment!


Do your kids like gross science? I feel like the grosser, the better with our kiddos. And this was actually one of my favorite experiments I did with my mother growing up. It's a great way to teach the very basics of biology, reinforce the concept of the scientific method, and get your kids used to real experiment techniques. It sounds complicated, but it's very easy. However, because you are dealing with biological materials here, make sure an adult seriously supervises this activity and properly disposes of any bacteria that grows.

Here's what you'll need:
- pre-poured agar plates (you can find them at a scientific supply store or online);
- sterilized swabs
- tape
- plastic baggies
- a cardboard box just big enough to hold the agar plates

First, have your kiddos come up with a list of places/things they'd like to swab for bacteria. Remove your agar plates from storage and let them come to room temperature (if you don't use them within a few days of purchase, it's best to store them in the refrigerator. Just remember to store them upside down so condensation doesn't collect on the agar).

Carefully dip the tip of a swab into water and swab whatever object your kids have picked. Help your kids remove the lid of the agar plate and gently streak, in a zig-zag motion, the swab over the surface of the agar. Carefully dispose of the swab.

Place the lid onto the agar plate and secure with 2-4 pieces of tape. Have your child help label the lid with whatever item you've swabbed.

Once you've swabbed all your items, place the sealed agar plates (invert the plates to prevent condensation issues) into a cardboard box and seal closed. Place the box somewhere warm in your home.

After about 2-4 days, you'll start to see some fantastic bacterial cultures grow! Have an adult carefully place each agar plate into a sealed plastic bag for the kiddos to observe -- you don't want to risk the kids opening up the culture. When you're done, make sure you responsibly dispose of the cultures.

We swabbed all kinds of random things with a variety of results. Some things were reassuring -- my computer keyboard grew surprisingly little bacteria. Some results were life changing -- let's just say Cam might have gotten a new carseat after we swabbed her cup holder. You just never know what things are going to sprout up!