We conducted an experiment to find where the most germs lurk in our house- YUCK! Since I did this experiment with my oldest son years ago, I already knew the most obvious places like toilet handles may not always yield the most bacteria but I remained silent as my middle sons made their hypotheses.
In place of petri dishes, we used lids to old containers. For an agar substitution, you can mix a half cup water mixed with 4 small packets of clear gelatin mix. Stir until mixture thickens and then pour a thin layer into sterilized lids or petri dishes. Place each dish into a small Ziploc baggie and seal. Let liquid harden into a gel, which usually takes about 30 minutes.
Next is the fun part (or gross part if you are a clean freak like me). Cordially invite some germs to come an live in your dishes. Use Q-tips to pick up germs from places you think that may have the most germs, such as door knobs, telephone, keyboard, toilet handles, and the refrigerator handle (you must include this one as it sometimes has the most surprising results.)
After rubbing a Q-tip along the surface of an object, immediately run the swab through the top of the gel. You should see a small groove on the surface. Place the dish back into the baggie and reseal. Label the baggie with the area you tested, and place it in a dark place for at least three days. Be prepared to be disgusted to see the results- so gross yet strangely fun. :)
While waiting for the germs to grow and become visible, we read The Magic School Bus Science Chapter Book #6: The Giant Germ It uses common language to explain what a germ is, and it teaches about microbes, fungi, protozoa, bacteria, and viruses. It's a great introductory book for microbiology. The Magic School Bus Series is a classic series for making science fun.
We also watched a fantastic video of how the body fights germs. Ralphie becomes ill so Ms. Frizzle and the gang travel inside his bloodstream.
A few years ago, my kids used this science kit, The Magic School Bus: The World of Germs, and they really enjoyed it.
Now I need to go wash my hands. All this writing about germs is making me become germaphobic.
Enjoy making yucky stuff fun to learn about!