Procedure for Exercise B
- Obtain from your instructor several pctri dishes containing culture medium. Sclcct locations for exposing the pctri dishes. If the weather is mild, you might choose several outdoor settings, such as a wooded area, park, city street, and suburban lawn. Sclcct at least one indoor location as well. If it is winter or raining» you might want to sclcct all indoor locations. Your instructor may specify certain locations or have other suggestions. Also, you might want to expose the plates at different times of the day to sec if the same types of fiingi are present at different times.
- When you arc at cach location, remove the lid from the dish. The open dish should be exposed for 10 minutes. Do not put the dish on the ground. After the 10 minutes arc up, close the dish and tape the lid on. Be sure to write the location and your initials on the lid.
- Bring the exposed pctri dishes back to the lab. and place them in the room-tcmpcrature location your instructor indicates. Make sure natural light is available, since many fungi need light-dark cycles in order to develop. Allow the cultures to remain undisturbed during the incubation period.
- After 3 days, chcck the cultures for growth. After 5 days, count the number of colonics. It is usually easier to count the colonics from the reverse side. Be sure to keep the lids closed. Remember that spores arc easily airborne and many people arc allcr gic to the spores.
- Record the number of colonics and answer the questions on worksheet 18-1 at die end of this laboratory topic.
EXERCISE C: Fungal Foods and Fermented Products
I jfe would be dull without some of the products of fungi. Many mushrooms and other fleshy fungi arc eaten as vegetables or gourmet delicacies. Fungi arc responsible for the formation of several cheeses; camcmbcrt and blue cheese (including Gorgonzola, Roquefort, Stilton, etc.) are the product of fungal metabolism. Your instructor may have some of these available in lab.
The activities of yeast produce both bread and alcoholic beverages through the process of fermentation, die anaerobic respiration of glucose to producc cthanol and carbon dioxide. The glucosc is only partially broken down, and only 2 molecules of ATP are produced for each molecule of glucosc. In baking bread, the carbon dioxide causes the dough to rise (the alcohol vaporizes during baking). In brewing, the alcohol is the product of interest, and the carbon dioxide usually bubbles off. Bodi beer and wine are produced through fermentation by yeast. In this exercise, we will inoculate grape juice with two different types of yeast (champagnc yeast and bakers' yeast). We will chcck these later in the week for both carbon dioxide and alcohol production.
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