Fungi Chapter 25

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

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

Body plan: yeasts Unicellular Round, oval shape

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

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

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

Common black bread mold

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

Penicillium at 200X

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

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.

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

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

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

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

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

"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