Fungi

Part I
Fungi are eukaryotic organisms that lack the ability to carry on photosynthesis. Their nutritional modes reflect this fact. Their main role in nature is to act, along with the bacteria, as decomposers. Their external digestion of substrate materials allows them to breakdown or degrade organic materials. These materials can then be absorbed back into the fungi or into other plants. It is thought that most (over 80%) of plants have fungi that live in or around their roots. These fungi are known as MYCORRHIZAE.

Dependent on growth conditions, fungi exist as single cells known as YEAST or as threadlike tubular strands of cells called hyphae. Some of these hyphae ascend and support the spore producing structure. Fungi are classified into groups on the basis of their sexual reproductive structure, or lack of one. Other hyphae descend into the substrate and anchor and absorb materials for the fungi, acting in some ways like roots. The total mass of the hyphae make up the body of the moldlike fungus known as the MYCELIUM.

Four groups are currently recognized:

1. Zygomycota - contains the bread mold; most common is Rhizopus
2. Ascomycota - sexual structure is called the ascus and usually contains 8 spores; contains single-celled yeasts such as Saccharomyces and multicelled morels and truffles; there are some important parasitic members as well
3. Basidiomycota - sexual structure is the basidium which hangs down from the cap of the familiar mushrooms; also important parasites in this group
4. Deuteromycota - sometimes known as the Imperfect Fungi because we have not identified a sexual reproductive structure yet; ringworm causing organisms as well as Penicillium and Aspergillus are in this group

Use the links in the table below to learn more of the structure and function of the various organisms in the fungal groups.

See also pages 47-56 in A Photographic Atlas for the Biology Laboratory, 4th Edition.

Part II
Follow these links for a fun way to grow your own fungi at home. There are a number of factors, both physical and chemical that can easily be tested at home. Try two or three of these.

1. the effects of temperature on fungi - put bread and a moist paper towel in a boilable plastic bag and microwave for two minutes. Be sure paper is still moist. Prepare a second slice and moist towel but omit the microwave step. Incubate at room temperature and record time of first growth and which type of bread.
2. the effects of salt - use moist towel, bread and salt the surface of one piece of bread but not the control. Incubate at room temperature and compare results.
3. dry bread versus moist bread
4. bread made with preservative and without
5. the effects of sugar or sugar substitutes on fungal growth