Classification of Fungi

Fungi have been classically characterized and classified by the appearance of their colony (color, size, etc), hyphal organization (septate or coenocytic), and the structure and organization of reproduction spores. More recently, however, ribosomal RNA sequences are being used to further categorize these organisms. Many disagreements exist in the literature regarding the placement of several genera into their respective phyla. The following classification scheme is based largely on Prescott et. al., Microbiology. Some useful information regarding hyphae type was retrieved from http://bugs.bio.usyd.edu.au/learning/resources/Mycology/contents.shtml and http://bugs.bio.usyd.edu.au/learning/resources/Mycology/StructureFunction/introduction.shtml. We will look at six fungal divisions. Two more (Urediniomycetes and Ustilaginomycetes) are often classified as Basidiomycota and as such are not listed as separate divisions here.

Table #1:

Chytridiomycota (chytrids):
The simplest of the fungi, the chytrids are microscopic and found in freshwater, mud, soil and sometimes the rumen.

Zygomycota (bread molds):
Members of the subdivision Zygomycota have coenocytic hyphae. Asexual reproduction is via sporangiospores, which can be released from the sporangium and carried by air currents. When the spores reach an appropriate substrate, they germinate to produce new hyphae. Bread molds do not usually cause human disease. In fact, in some countries they are used in food production. Rhizopus, however, is an opportunistic human pathogen; it is especially dangerous to people with diabetes mellitus that is not well controlled.

Ascomycota (sac fungi):
Members of the subdivision Ascomycota include molds that have septate hyphae and some yeasts. They are called sac fungi because their sexual spores, called ascospores, are produced in a sac or ascus. Asexual reproduction is via conidiospores. The Ascomycetes include fungi that cause chestnut blight and Dutch elm disease. Claviceps purpurea is a parasite on rye grass that causes ergot.

Basidiomycota (club fungi):
Basidiomycetes also possess septate hyphae. The sexual spores, called basidiospores, are produced by a club-shaped structure called a basidium. In mushrooms the basidia are found along the gills or pores on the underside of the cap. Some mushrooms produce toxins that are lethal to humans.

Glomeromycota (mycorrhizae)
Most are mycorrhizal fungi that form a mutualistic symbiosis with the roots of plants.

Microsporidia
Obligate intracellular parasites of fish, humans and insects

Rachel Watson, M.S.
AG 5010
766-3524
Cell: 307-760-2942
rwatson@uwyo.edu