BSCI 124 Lecture Notes

Undergraduate Program in Plant Biology, University of Maryland

LECTURE 16 - Eukaryotes/ Fungi

1. Kingdom Fungi
   
   1. General characteristics [Slow to load but thorough and excellent with numerous illustrations.]
      1. Eukaryotic
      2. Non-photosynthetic, obtain their nutrients by assimilation (produces digestive enzymes to predigest food before absorption)
      3. Cell wall of chitin (like insects) and/or cellulose
      4. Morphology
         1. Most fungi: thread-like strands (hyphae- collectively, mycelium)

            -barely visible by itself but can grow into large expanses- largest living organism is reported to be a fungus growing across 15 square miles in Minnesota

         2. Other fungi: single-celled, like large bacteria, called yeasts
         3. Form spores that can spread by wind, air or soil

            -Sexual spores (through mitosis) - e.g. mushroom is a spore-producing structure, formed from many fused hyphae

            -Asexual spores (through mitosis alone)- partly why they are so successful

   2. Significance to humans
      1. Beneficial fungi
         1. Decomposition in the biosphere example: wood-rotting fungi

            -because fungi obtain their nutrition from organic matter, they grow wherever organic matter is present- recycle nutrients from dead matter

         2. mycorrhzae fungi grow into roots of most plants and supply phosphorous and water.
            1. 90% of plants require this growth of fungi on their roots in order to survive- actually is a problem with reforestation of barren land because the fungi are not present
            2. symbiosis between the fungus and the plant- fungus gets sugars from plant and fungus provides phosphorus and water to the plant
         3. Produce antibiotics -penicillin produced by Penicillium species , discovered by Alexander Fleming in 1928; won the Nobel Prize in 1945
      2. Pathogenic fungi- fungi grow within host, using host as food for replication
         1. Human diseases - athlete's foot, ringworm, Candidiasis- AIDS patients are particularly susceptible to lung infection by Aspergillus, Cryptococcus (soil fungus)
         2. Mycotoxins are toxic chemicals produced by fungi which accumulate in infected food

            e.g.:

            i) corn or peanuts contaminated with aflatoxins.  Aspergillus fungi grow on corn or peanuts and make one of the most potent carcinogens known- aflatoxins.

            ii)  Ergot of rye- a fungus infects the flowers of the rye plant and produces fungal structures in the seedhead which are harvested with the rye seed. Eating the Ergot-infected rye are poisoned by compounds produced in the fungus structure- called Ergotism or St. Anthony's Fire- nervous spasms, convulsions, psychotic delusions, constriction of blood vessels that lead to tingling in arms and legs and possibly gangrene.  In 944, caused over 40,000 deaths.

         3. Plant diseases -Diseases you may notice around home/garden/campus: lawn diseases apple scab fire blight of orchard trees tree leaf diseases. Also epidemics (wide spread diseases which wipe-out a host plant over a wide area) of significance: loss of chestnut trees in North America, loss of American Elm trees to the Dutch Elm Disease (here too) and Irish potato famine (in contemporary newspaper articles)
      3. Commercial uses
         1. Yeast - fermentation. Yeast breaks down sugars to produce ethyl alcohol and carbon dioxide (CO₂)
         2. brewing of alchoholic beverages: beer , wine- yeast turns sugars in grains or grapes into ethyl alcohol (and carbon dioxide bubbles)
         3. bread making where yeast turns sugars into alchohol and carbon dioxide, produces bubbles that rise the dough
         4. Edible fungi - mushrooms, morels, truffles, and the latest fad kombucha! - all are sexual fruiting structures of fungi, the mycelium remains
         5. Cheese production: Types of cheeses - blue cheeses such as Roquefort, Stilton, and Camembert
      4. Others
         1. some poisonous; see also this site- some used as intoxicants as far as 4,000 years ago
         2. some hallucinogenic
            
2. Illustrations of varioushref="http://muse.bio.cornell.edu/~fungi/fgeneral.html#IMG">fungi

Others Sites of Interest:
Fun Facts About Fungi-fungi that kill insects, fungal shotguns
Learn more about Fungi
Genera of Fungi: technical
Mushrooms
Links to Yeasts
Index to Mycological Resources
Fun (and serious) stuff about fungi
Kombucha:
Mushroom Picker's Primer
Human diseases caused by fungi
Thanksgiving dinner

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Last revised: Feb. 10, 1999 - Straney