I posted before about this awesome science kit J got for his birthday (it came from Toys R' Us). I thought I'd share one of his experiments. The kit came with everything you need to take samples and grow bacteria.
The Mister used sharpie on the back of the petri dishes to separate the dish in half, then he put masking tape on the back and wrote down where each sample came from. By separating the dishes in half, they were able to take twice as many samples with a single batch of agar.
He and J took samples from around our house including the inside of J's nose and the bottom of his feet.
It took about a week to grow decent samples. I can't remember what the instructions say in the kit but here's a few tips we know from our own microbiology studies:
1) Store the petri dishes upside down while growing bacteria, otherwise condensation will collect on the inside of the lid and drop back down onto the agar, effectively drowning your samples and spreading bacteria around the dish.
2) To grow samples you need to store your dishes in a warm, dry, dark place. Once you have good samples you can store the dishes in the fridge to prevent the samples from growing more.
3) Since most people don't have a incubator in their home, any warm, dry, dark place will work. We used the inside of a cabinet. Feel free to check your samples for growth each day, but keep in mind that it may take about a week to get good growth.
4) This is a great time to explain the necessity for safe science practices. You are growing germs after all, don't forget to explain to your little scientist that they shouldn't handle the samples with their hands, and make sure to wash everything when you're done with soap and water (especially your hands!). It's also a good idea to rinse the petri dishes with bleach water before using them for another experiment.
The experiment provided with the kit technically stops there but we decided to take things a bit further since we had the necessary equipment and J was interested.
I won't go threw the whole scenario, but we replicated a microbiologists methods of taking samples from the petri-dishes and transferring them onto a slide. Since we didn't have the various dyes as our disposal, we used red and blue food coloring to wash J's samples. It worked rather well.
Here he is rinsing his samples.
I tried to find some easy to follow directions online for this process, but I'm not having much luck. Without some knowledge of the workings of microbiology, the terminology seems a bit scary. This link contains instructions from a student's lab book that are fairly good.
Here is a picture of his sample under the microscope! J loves using the microscope and his samples turned out really well. He was able to find his samples in the microscope and The Mister gave him a mini lesson on identifying various shapes.
This website has great images depicting the various microorganism shapes commonly found.
We started out with a Magic School Bus microscope kit, which was extremely poor quality and after J showed a real interest in microbiology, we purchased this microscope from Toys R' Us by Edu Science about six months ago for $50.00. (The pre-made slides that are in the picture were given to J as a gift but came from a local education store, they can also be found online). We have been extremely happy with this microscope. It actually works, which is hard to find in an inexpensive microscope. It has its own light source which I think is a must, and comes with a removable cord, or can be used with batteries so you're not tethered to the wall. It also has an adjustable light source (we were using red in the picture above) which helps when trying to view various samples.
J is still learning the fine details of microscope work, but he is able to set up a slide, find his sample, and use the fine adjustment knob to get it into focus. He likes to share all of his finds so it's easy for me to verify that he's actually seeing what he's supposed to. One of these days I'm hoping he'll get more interested in recording what he's seeing, but I'm not pushing the issue.