Growing Simple Bacteria in Petri Dishes
    This experiment allows you to investigate bacteria in your environment and develop an understanding and appreciation of hygiene, sanitation and community health.
    Sources of bacteria could be from: drinking fountains, tabletops in fast food restaurants, door knobs in public restrooms, dirty hands, money, the sink drain, the kitchen sponge and countless other everyday sources.
    A possible experiment would be to grow bacteria from one or more of these sources and then see if the antibacterial soaps or cleaners really work on destroying them. You can also try growing the bacteria in a variety of different environments; darkness, 24 hour light, warm, cold, moist, etc.
    It is most important to use proper sterile techniques when conducting your experiment, so additional bacteria is not introduced accidentally into the Agar. Thoroughly clean all work areas and equipment that will be used. Your petri dishes are already sterile, keep them sealed until ready to pour the Nutrient Agar.
    Tri-Ess Nutrient Agar is what you will use to grow the bacteria on. It is a special formulation of Agar and Nutrients for culturing molds and simple bacteria. A unit of 33 grams is sufficient for a package of 20 petri dishes. 

STERILIZING TECHNIQUES:
    Lip of the flask: when pouring sterile culture media from a flask to sterile petri dishes, remove the cotton stopper and flame the lip of the flask to kill all existing bacteria that are clinging to the outer rim.

PREPARATION OF MEDIA AND DISHES
    Place contents of bottle in one liter of distilled water. Preparation should be in an Erlenmeyer Flask. If one is not available use any Pyrex cooking vessel. Bring to a boil and simmer until all materials are dissolved. It is necessary to intermittently stir with glass rod so Agar will not burn. As soon as the Agar has completely dissolved, remove from heat and plug flask with large plug of non-absorbent cotton. Allow to cool to 45ºC.
    Do not contaminate media. Clean table with a disinfectant. Close doors and windows to minimize air circulation and spread of air-borne bacteria. Line petri dishes along the edge of the table, being careful not to open lids. Remove cotton plug from flask, flame lip and pour into petri dish to a depth of 1/3 full or 10 to 15 ml. Flame lip and repeat procedure with each dish. Open petri dish only enough to accept lip of the flask and close immediately. Allow filled dishes to sit until media has solidified (approximately 24 hours).

INOCULATION (TRANSFERRING BACTERIA)
    To inoculate the media use a transfer loop or sterile swabs to transfer. Remember to flame your loop before and after each procedure. Open the petri dish enough to insert the loop and quickly but lightly trace the letter "Z" across the surface of the media. DO NOT BREAK THE SURFACE OF THE MEDIA!! Touch very lightly. Close cover and set aside to incubate.

INCUBATION:
Incubation can be done at various temperatures. Many forms of bacteria will grow at room temperature while others need higher temperatures. A simple incubator can be made from a cardboard carton. Use a carton that has all flaps intact. Cut a window in the front  and tape in a piece of plastic, cellophane or saran. Suspend a light bulb in the center through the top. The size and position of the bulb can be determined by placing a thermometer on the floor of the incubator. Vary the height and size of the bulb so that you have a constant 95° temperature. To prevent condensation from forming, the dishes may be placed inverted in the incubator. Growth will appear usually within 48 to 72 hours.

SLIDE PREPARATION
To prepare bacteria for simple staining, use a clean slide. Slides (Tri-Ess Part # M340) should be washed first with cake Bon Ami (available at most supermarkets in the cleaning section), allowed to dry and then polished with a clean tissue and air dry again. Thereafter handle slides only by the edges.
    With a sterile swab or transfer loop, transfer a suspension of the culture to the center of the slide. Do this so that a thin, even film is deposited on the slide. Allow to air dry and then "heat fix" by passing the slide rapidly through a flame two or three times. Be certain that film is up. Staining is accomplished by flooding the smear with two or three drops of Methyl Blue Solution (available at Tri-Ess 1/2 dropper bottle: $2.00) stain and allowing it to remain for various intervals of time depending on the stain and the culture. Wash carefully with an indirect method and allow to air dry. Mount cover glass (included in M340 slides)  with cement (Tri-Ess Part # M354, label (Tri-Ess Part # M334) and slide is ready for viewing.

Many other project ideas and supplies are available.
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