Do Odor and Bacteria Go Hand-in-Hand?

Grade Levels: 3 - 8

You know how sneakers get during those hot summer months when you wear them all the time, sometimes without socks? They get kind of, well ... stinky.

This is especially true if you get them wet in the creek one day and then forget to put them out in the sun so they dry properly. Damp, dirty sneakers can get really, well ... stinky.

Does that smell, though, mean that your sneakers are filled with bacteria and are unsafe to wear? Bacteria are everywhere, from mountaintops to the bottom of the oceans. Bacteria, which is the plural for bacterium, have even been found in frozen rocks in Antarctica.

In this experiment, you'll test your sneaks against some other, less smelly objects, to see if smell and bacteria might be related.

You'll need to get some petri dishes that contain nutrient agar before you begin your experiment. You can get these at a biological supply company, or your science teacher might be able to give you a few.

Round up some objects that you want to test, and the most stinky pair of sneakers you can find. Be sure to choose a variety of objects, such as the pencil you use to do your homework, the doorknob of your front door, the inside of your bathroom sink, and so on. Test as many places as you like, as long as you have a petri dish in which to transfer any bacteria you collect.

Be sure to record detailed observations about the objects you're testing, including the following:

  • Does the object appear to be clean or dirty?
  • Does the object smell bad?
  • Where was the object located?

Using a clean cotton swab, wipe the surface of the object you're testing, and then wipe the swab across the surface of the petri dish. Be sure to label each dish, so you know which object the sample was taken from.

Cover the dishes and put them in a warm, dark place where they won't be bothered. Check them twice a day-once in the morning and once at night-for a week, and record your observations about what's happening.

After a week, you'll be able to see which items you tested contained the most bacteria. Were they the dirtiest-looking items? The smelliest ones? Make a chart on which to record your findings, then be sure to dispose of the petri dishes properly. And, just a thought ... if your sneakers turn out to be the vacation spot of the world for all kinds of bacteria, you might want to talk to your mom or dad about getting a new pair!

Excerpted from The Complete Idiot's Guide to Science Fair Projects © 2003 by Nancy K. O'Leary and Susan Shelly. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.

To order this book visit the Idiot's Guide website or call 1-800-253-6476.

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