Bacteria grow in a wide variety of conditions. They may be found on the tops of mountains, the bottom of the ocean, in the stomachs of animals, and in the frozen ice of Antarctica. In terms of evolution, bacteria are thought to be very old organisms, appearing about 3.7 billion years ago. One feature that has enabled them to spread so far, and last so long is their ability to go dormant for extended periods of time. Some bacteria cause disease, but most bacteria are helpful.



Bacteria are both harmful and useful within the environment, and to animals and humans. The role of bacteria in disease and infection is important. Some bacteria act as pathogens and cause tetanus, typhoid fever, pneumonia, syphilis, cholera, food-born illnesses and tuberculosis. Other bacteria help to decompose dying organisms to release nutrients back into the environment. Without this, there would be no photosynthesis in plants and consequently no food.

Antiseptic measures may be taken to prevent infection by bacteria, for example, prior to cutting the skin during surgery or swabbing skin with alcohol when piercing the skin with the needle of a syringe. Sterilization of surgical and dental instruments is done to make them sterile or pathogen-free to prevent contamination and infection by bacteria. Sanitizers and disinfectants are used to kill bacteria or other pathogens to prevent contamination and risk of infection. But which disinfectants (or cleaners) work the best?

To conduct your experiment you will need 18 agar plates or Petri dishes, masking tape,1 teaspoon each of Mr. Clean, Lysol toilet boil cleaner, Fantastik all purpose cleaner, Windex multi-surface cleaner, and Scrub Free bathroom cleaner (or any other cleaners you wish to test),10 sterilized q-tips and a dark place like a cupboard at room temperature.

Place different bacteria in several petri dishes that contain a special ingredient to help the bacteria grow. Here is how to do it: rub your fingers on 6 petri dishes,rub sterilized q-tips on the kitchen floor then rub them on 6 different petri dishes,rub the sterilized q-tips on a toilet bowl and then rub them on the 6 last petri dishes.

In each series of 6, leave one petri dish with no cleaning product to see how much bacteria will normally grow. On all of the other 5 petri dishes put a different cleaning product. Use exactly one tablespoon of each cleaning product in each petri dish. Now watch the bacteria grow.

OK, what have you found; which cleaning product works the best?