Week two of our study on bacteria continues swimmingly. Out of the eight plates grown from around the house, the boys chose two with robust colonies to transfer to new plates for tests of various household cleaners. Keeping colonies at the proper temperature and humidity challenged them last time, so my son’s friend designed an incubator for this and further experiments.
A styrofoam cooler serves as the body, with a notch on the side for a nightlight attached to an extension cord, which is hot-glue-gunned on the outside of the cooler. On the other side is a candy thermometer. The device maintains a steady 92 degree atmosphere with ample humidity (our plates in the box on the heat duct dried out significantly). Inside, plastic racks allow petri dishes to be separated, allowing room for air circulation. The bacteria are thriving in this simple, inexpensive incubator. This child has also offered to create a centrifuge. I’m taking him up on it.
This week, we’re discussing antibiotics and antibiotic resistance. They’ll design an experiment with some samples (which we’ll bleach down afterward — we don’t want to contribute to any resistance problems). While I have them do some labs that are of the “follow the directions and see what happens” type, I’ve worked in several inquiry labs, where they design the lab with minimal guidance and learn as they go. Both boys are much more interested in chemistry than biology, and they really froze up when asked to think of ways to, for example, explore enzyme activity, without a script. Interest level in the topic was key to their effort. I’m seeing improvement in the quality of their lab designs as they become more comfortable with the material, and I’ve learned to give them a bit more information before designing a lab than I did at the start of the year.
Stay tuned as they attempt to make their own growth medium using a pressure cooker (not the homemade variety). Stand back, we’re going to learn!