Fungi

1. Fungi Chapter 25

2. Characteristics • Eukaryotes • Heterotrophs • Feed by absorption rather than ingestion • Most are decomposers • Prefer moist habitats • Can survive over a wide of temperatures, pH, salt and sugar concentrations • Cells have cell walls containing chitin • Two types: molds (most) and yeast

3. Body plan: molds • Hyphae – long filaments that invade their food source and provide a large surface area to absorb nutrients • Mycelium – a tangled mat of hyphae • Some have cells separated by cell walls called septa, others do not – coenocytic • Even those with septa often have large pores that allow free flow of organelles between cells

5. Body plan: yeasts • Unicellular • Round, oval shape

7. Reproduction • Fruiting bodies (mushroom) – parts involved in reproduction • Reproduction can be either asexual or sexual – most fungi nuclei are haploid • Asexual: spores are produced in sporangia • Sexual: gametes are produced in gametangia

9. Types – generally classified by reproductive structures • Chytridiomycetes (chytrids) – most primitive group alive today • The only fungi to produce flagellated cells at some point in their life cycle • One form is responsible for declining amphibian populations

11. Types… • Zygomycetes – produce sexual spores called zygospores • Most are decomposers • Black bread mold

12. Common black bread mold

13. Types… • Ascomycetes – produce sexual spores in sacs called asci • Yeasts, powdery mildews • Dutch elm disease, ergot on rye plants, chestnut blight

15. Penicillium at 200X

16. Types… • Basidiomycetes – develop spores inside of club-shaped basidia • Mushrooms, bracket fungi, puffballs

18. Mushrooms are the spore-producing structures of some fungi. A mushroom consists of a stalk and a cap, and in most species the spores are formed on gills. When ripe, the spores fall downwards and are carried away from the mushroom on air currents. A spore that lands on a moist surface with nutrients can form a new fungal colony, but must mate with another colony of the same species before a new mushroom can be produced.

19. Types… • Deuteromycetes – ‘imperfect fungi’ – no sexual stage at any point in their life cycle

20. Lichens • Symbiotic relationship between a photosynthetic organism and a fungus • Mutualism or parasitism? • Fungus depends on the phototroph for food • It is unclear if the fungus provides water and nutrients in return

21. Ecological Importance • Significant in biogeochemical cycles as decomposers • Some are parasites – feed on a host’s body (athlete’s foot, e.g.) • Mycorrhizae – form mutualistic relationships with many plant species and help them extract nutrients from the soil

23. Impact on humans • Economic importance: • Production of ethyl alcohol, bread, cheese, soy sauce • Edible mushrooms • Production of penicillin and other antibiotics • Plant and animal diseases: • Chestnut blight, potato blight • Ringworm, athlete’s foot, candidiasis, histoplasmosis

24. Rust fungi are parasites of plants. Some of the disease symptoms they produce resemble rust particles on iron. These leaves of this have been infected by the rust fungus Phragmidium subsimile, which produces yellow–orange and black overwintering spore pustules

25. "Found in keratin-rich soil throughout the world, this fungus [Microsporum gypseum] produces an infection called ringworm on smooth areas of skin and on the scalp." —From "Body Beasts," December 1998, National Geographic magazine Photograph by Darlyne A. Murawski