Microorganisms Study Guide (page 2)

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Updated on Sep 20, 2011


The Kingdom Fungi contains single-celled organisms that are heterotrophic in the sense that they do not contain chlorophyll and cannot photosynthesize. Other fungi are multicellular and not microorganisms but function in much the same way as the microscopic forms. However, it is more accurate to describe the ability of multicellular fungi to obtain food in three ways. Saprophytic fungi consume dead organic matter, parasitic fungi attack living plants and animals, and mycorrhizal-associated fungi form close relationships with trees, shrubs, and other plants, where each partner in the relationship mutually benefits.

Fungi produce spores that are very resistant to temperature and moisture extremes. These spores can travel to new areas, thus spreading the fungi organism. The spores can survive for a long time, even in inhospitable environments. When conditions change and become more favorable, the spores germinate and grow. Food is absorbed through structures called hyphae. A large mass of interconnected, branching hyphae is called the mycelium, which constitutes the main body of the multicellular fungi. However, the mycelium is usually not seen because it is hidden throughout the food source being consumed.

What is most often visible is the fungal fruiting body. A mushroom is a fruiting body that contains the spores. The main body of the mushroom (the mycelium) is under the soil surface. An organism called lichen is a mutually beneficial union of a fungus and an algae. Because fungi consume dead organic matter, they play an important decomposition role in an ecosystem. Their actions return nutrients to the soil for eventual uptake by plants.

In Short

The general grouping of microorganisms (microbes) includes the bacteria (one-celled organisms without a true nucleus, also called prokaryotes) and the protists (one-celled organisms with a true nucleus, also called eukaryotes, along with all other organisms besides the bacteria). Single-celled fungi (yeasts) are also microorganisms, but multicelled fungi also exist in abundance. We are completely dependent upon the action of microorganisms, and many more of them are beneficial rather than harmful.

Practice problems of this concept can be found at: Microorganisms Practice Questions

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