Science Buddies: "Ask an Expert"

I'm testing natural products against each other to see which one is most effective at killing household bacteria. (I am in middle school and know I need to be extra careful about bacteria, so I'm using a face mask and goggles.) So, I have the question, hypothesis, purpose and most of the materials figured out. Now, I have to figure out a couple more things so I can get started: Shouldn't the household bacteria I use be controlled? I was going to spread bologna on a tile like I saw on Myth Busters, but now Kraft foods has started putting additives on their meat to prevent bacteria. So that's out. what other food could I use that would grow bacteria that's not too dangerous? Or should I get the bacteria from a sponge that has been used around the house? Also, when I repeat the tests, should I do them all at the same time so the temperature and other conditions will be the same? Thank you for any help. I need to turn in my method process proposal very soon.

You should still be able to use bologna. Use a local store brand (it will save money too) and should not be too difficult to maintain a good level of specimens.

As for doing the actual counts, yes, you should try to do them in as controlled environment as possible. Same temperature, time of day and location (with no natural light or airflow, if possible).

As for using the kitchen sponge, you'd be surprised how effective current cleaning solutions are at killing bacteria-- you may end up with a nice clean sponge by the time you need to do your test counts...