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The Major Groups of Fungi Help

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By — McGraw-Hill Professional
Updated on Aug 30, 2011

Introduction to The Major Groups of Fungi

More than 100,000 different species of fungi have been identified, yet mycologists (my- KAHL -uh- jists ) – “those who specialize in the study of fungi” ( myc ) – usually group all of these species into just four different phyla. The names of these phyla are very tongue-twisting! Nevertheless, a helpful hint is that each phylum name ends with the suffix, - mycetes (my- SEE -teez), which comes from the Greek for “fungus” ( mycet ). So, look for and recognize -mycetes, and you know a fungus is somehow involved!

Phylum Basidiomycetes (the Club Fungi)

A good fungal phylum to start with is the Phylum Basidiomycetes (bah- sid -e-oh-my- SEE -teez). The Phylum Basidiomycetes includes mushrooms, puffballs, and the shelf fungi often seen growing on the barks of trees. This particular fungal phylum, then, is quite familiar to those of us who like to walk through woods and fields (or even stroll through our own backyard).

The mushrooms get the first part of their phylum name from their basidia (bah- SID -e-uh) – the “little bases” ( basidi ) growing out from the gills under their caps (see Figure 8.3). This group is therefore called the Basidiomycetes (“little base fungi”) or club fungi because of the tiny, “club”-shaped basidia present along the edges of their gills. The basidia are important because they produce the mushroom’s spores, which can be blown off from under the cap and distributed long distances by the wind.

The Fungi: Not Just Mushrooms! The Major Groups of Fungi Phylum Basidiomycetes (the Club Fungi)

Fig. 8.3 The basidia: “Little bases” or “clubs” on mushroom gills.

Phylum Ascomycetes (the Sac Fungi)

You might also encounter various members of the Phylum Ascomycetes ( as -koh-my- SEE -teez) or “leather bag” (asco-) “fungi” as you walk through a forest. This group is commonly called the sac fungi, because they produce spores within their sac-like or bag-like caps. Consider, for instance, the very popular morel mushroom, often nicknamed spongy-cap due to the wrinkled, sponge-like appearance of its cap.

Much less dramatic members of Ascomycetes, however, are the unicellular yeasts. Yeast cells reproduce by smaller cells budding off and eventually separating from larger ones. Yeast belonging to the genus Saccharomyces ( sak -ah-roh- MY -seez) are the main “sugar” (sacchar) “fungi” (myc). This genus of yeasts has been used to help make bread, beer, and wine since ancient times. The yeast cells are added to raw bread dough or a vat of grape juice, and they soon begin to consume lots of sugar molecules in the dough or juice. Initially, these Saccharomyces organisms operate aerobically, utilizing oxygen. The yeast cells give off CO 2 gas as a waste product, and these gas bubbles are what make bread dough rise! Later, when the bread is finally baked, the yeast cells are killed by the high temperature of the oven.

During winemaking, in contrast, the sealed wine vats become anaerobic, after the active yeast cells consume all available O 2 . The yeast cells then switch their metabolism from aerobic to anaerobic, and carry out the process of alcoholic fermentation ( fer -men- TAY -shun). By this process, yeast cells produce both carbon dioxide and ethyl alcohol (common drinking alcohol) as waste products. When the fermenting wine reaches an alcohol content of about 12–16%, the yeast cells become poisoned and die from too much alcohol!

Some common types of molds are also considered members of the Phylum Ascomycetes (sac fungi). In general, a mold is a fuzzy coating of fungus growing on the surface of some food or animal or plant substances, when they are decaying or left for too long in a moist, warm place. A familiar example of such a fuzzy mold is the genus Penicillium ( pen -ih- SIL -e-um), named from the Latin for “brush.” The Penicillium fungi are bluish-colored molds growing on bread, fruits, and cheeses. They have a somewhat brushlike appearance under the light microscope, and several Penicillium species produce penicillin , the powerful, bacteria-killing, antibiotic drug.

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