Lab 1: The Prevalence of Microbes in the Environment

Purpose: To illustrate that microbes are found almost everywhere in profusion and variety.

Materials:

1. Total Count Easygel and special petri dishes for one dish per student.
2. Bunsen burner, alcohol lamp or candle.

Procedure and Comments:

1. Place special dishes on a level table along with a bottle of Easygel and a flame (burner, lamp, or candle).
2. Carefully remove the Easygel bottle cap. Be careful not to contaminate the lip of the bottle by touching it
3. Lift a petri dish lid and pour the Easygel into the dish. Replace the lid and swirl by rotating on the table top until the entire petri dish bottom is evenly covered with the Easygel medium.
4. Allow the dish to remain flat on the level table until the Easygel has solidified. This will probably be 45 minutes. You might wish to pour the dishes one day for use the following day.
5. Upon solidification of the Easygel , each student may take a dish for inoculation. The dish may be inoculated in any one of an endless variety of ways. Having an insect walk on the medium, blowing dust or dirt onto the surface, touching the medium surface on a doorknob or drinking fountain handle, kissing the Easygel surface, or putting your fingerprints on the medium are a few suggestions. After inoculation, the dish is ready to incubate.
6. Try to incubate at a temperature close to the natural environment from which the inoculum originally came. For example, if you touched the medium, incubate at 35-37°C which is close to your body temperature. Check for growth at 24, 48, and 72 hour intervals if possible.
7. Try to count the total number of colonies growing on your dish. Look for differences in colony size, shape and color.  Sometimes so much growth occurs that individual colonies cannot be distinguished. Lift the lid slightly and check for any odor. Look for fuzzy mold colonies as well as typical bacterial colonies.

Questions:

1. How many colonies are growing on your dish?
2. How many different kinds can you see based on size? shape? color?
3. Why do some colonies spread rapidly on the medium surface while others do not?
4. What causes the odor you detected?
5. How do molds differ from bacteria? List several ways?
6. At what temperature did you incubate your dish?
7. How should you destroy things growing in your dish?
8. Why should you destroy them?

Finished? Then move on to Lab 2: Pollution - The Overabundance of Nutrients
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