Bacteria are everywhere. They have evolved the ability to inhabit almost every surface on the planet; however, they are invisible to the naked eye due to their small size. Bacteria have been found living in the deepest part of the ocean, in volcanic vents, in boiling hot springs, and even deep in polar ice caps. Many species of bacteria live inside of other organisms in a harmless commensalistic way such as the intestinal bacteria, Escherichia coli. Bacteria can reproduce at very rapid rates whenever conditions are favorable, as often as every 20 minutes doubling in number. The bacterial population is kept in check by the natural defenses of the host, such as the immune system and proper washing habits. When these natural defenses fail, bacteria can quickly become a problem. Some bacteria produce poisons or toxins that can be life-threatening if the bacterial population isn't controlled by our natural defenses.
The United States Centers for Disease Control (CDC) states that the best way to prevent bacterial spread and infection is through the use of proper sanitary techniques. Perhaps the most critical step in this prevention is the use of proper hand washing. When improperly washed, your hands are one of the most easily colonized areas of your body and many of our behaviors involve the use of our hands. Proper hand washing requires the use of water as hot as you can stand, soap, and lots of rubbing. The soap and water serve to destroy bacteria, and the rubbing helps slough off dead skin cells along with lots of bacteria.
Students will examine:
Materials (Part A):
Black light, Glo-Germ powder, lotion or Glo-Germ oil, hand soap, water, paper towels, pencil, lab sheet
Procedure (Part A):
Data Table 1
|Time of Wash in Seconds||Percent of Hand Covered with "germs"|
|0 (initial observation)|
Materials (Part B):
Tennis ball, "play" money, stuffed toy, pencil, lab sheet
Procedure (Part B):
Data Table 2
|Name of Item||Percent Coverage|
|Initial Hand Coverage|
Create a graph based on the data from table 1.