Check out theBacteria CD-ROMwhich includes similar activities.

In recent years, a number of antibacterial soaps and detergents have been introduced. How effective are they at killing germs? Do all of them work the same, or does their effectiveness differ among brands? In this activity, you?ll test different antibacterial soaps.

• four petri dishes with sterile nutrient agar
• three different antibacterial soaps (hand soaps, dish soaps, or a combination)
• three medicine droppers
• wax pencil
• adhesive tape

1. Wash your hands with regular soap. Then run your fingers across your desk or another surface.
2. In each of the four petri dishes, wipe your finger through the sterile agar in a zigzag motion.
3. Use the adhesive tape to seal one petri dish. Mark this ?control dish A? with the wax pencil.
4. Use a medicine dropper to transfer a drop of the first soap to another petri dish. Write the type of soap in this dish on the worksheet. Seal the petri dish with tape, and label it ?B?.
5. Repeat step 4 for the second and third soaps, using a different medicine dropper and petri dish each time. (Label these petri dishes ?C? and ?D.?)
6. Place all four petri dishes in warm environment. For the next three days, check the dishes, and write your observations in theworksheetchart. At the end of the experiment, answer the worksheet questions.