FUNGI Chapter 31

The Little Known Fungi  100,000 species known, 1.5 million unknown (estimate)  Some are single-celled (yeast), but most multicelled (mushrooms)  Found in every habitat  Diverse, widespread, and essential for well-being  Formerly classified as plants  Molecular data says more closely related to animals  Mycologists are the scientists that study fungi

Nutrition  Heterotrophs, but absorb food instead of digest  Secrete enzymes into environment to break complex molecules into something more manageable  Enzymes also disrupt walls of plant cells for nourishment  Live as decomposers, parasites, or mutualisms'  Fit into multiple niches  Can digest wide range of food sources

Body Structure  Most grow as filaments and yeasts  Yeast only growth is rare  Bodies form filamentous networks called hyphae  Form a mycelium to increase SA/volume ratio  Proteins synthesized to rapidly extend (not grow) hyphae Concentratie of energy and resources to accomplish  Not motile, but can move hyphae

Specialized Hyphae  Some allow predation of living animals  Haustoria allow nutrient extraction or exchange  Mycorrhizae are mutually beneficial relationships between fungi and plants  Improve mineral delivery to plants in exchange for carbs  Ectomycorrhizal fungi: form a sheath of hyphae over plant roots and between plant cells  Arbuscular mycorrhizal fungi: extend hyphae through root cell walls and into plant

Sexual Reproduction Hyphae release pheromones Different mating types attract Heterokaryon, nuclei don’t fuse right away Dikaryotic, nuclei pair off and divide without fusing Time to karyogamy varies Usually only 2n stage Final steps generate genetic variation

Asexual Reproduction  Varies widely among fungi (like sexual)  Produce haploid spores by mitosis  Informally known as molds if mycelia is visible  Grow rapidly and reproduce sexually if contacted by species of different mating type  Yeasts produce budding cells or spores via mitosis  Deuteromycetes reproduce asexually only

5 phyla recognized currently, but chytrids are likely paraphyletic Study cycle diagrams for reproductive differences Fungi Functional Groups Chytridium globular fruiting bodies, one of the earliest to diverge Mucor, grow into fruits and breads; may act as decomposers, parasites, or symbionts Ecologically important; form mycorrhizal associations with plants Sac fungi, common to water and land Aleuria aurantia Decomposers and ectomycorrhizal fungi; fruiting bodies commonly called mushrooms

Phylum Chytridiomycota  Called chytrids and found in lakes and soil  Decomposers and pararsites of protists, other fungi, plants, or animals  Live in sheep GI tracts to help process plants  Some form colonies with hyphae, others as single cells  Only phyla with flagellated spores called zoospores

Phylum Zygomycetes  Reproduce by zygospores  Sexually, formed in zygosporagium  Asexually, formed atop sporangiophores  Rhizopus stolonifer is black bread mold  Know the life cycle  Philobolus ‘aim’ and shoot sporangium  Resistant to freezing and drying

Phylum Glomeromycetes  Form arbuscular mycorrhizae  Tips of hyphae push into plant root cells and branch into treelike structures  Minerals to plant and organic compounds to fungi  Mutualistic partnership with 90% of all plant species

Phylum Ascomycetes  Reproduce sexually by spores in asci (sacs) and bear stages in ascocarps (fruiting bodies)  Reproduce asexually by conidiospores, spores formed at tips of hyphae called conidiophores  Include: morels and truffles  Yeasts used in beer industry

Phylum Basidiomycetes  Includes mutualists that form mycorrhizae and plant parasites  Reproduce sexually by producing fruiting bodies called basidiocarps  Produces 4 haploid nuclei  Asexual reproduction is rare

Fungal Phylum Review

Decomposers  Any carbon containing substance can be consumed by some fungi  Important use in bioremediation  Maintain essential inorganic nutrients for plant growth  Return nutrients to the soil

Mutualists  Fungus-Plant  Ascomycetes benefit by producing toxins to deter prey  Fungus-Animal  Decomposers convert otherwise indigestible plant material  Lichens: symbiotic association with algae  Algae contribute carbon compounds and fix nitrogen  Fungi contribute suitable environments for growth  Reproduce separately Lichen: asexually via soredia, clusters of hyphae with algae

Pathogens  Mostly on or in plants  Ascomycete Cryphonectria parasitica attacks chestnuts  Basidiomycete Puccinia graminis causes black stem rust on wheat  Ascomycete Aspergillus contaminates improperly stored grains and peanuts by secreting carcinogenic aflatoxins  Mycosis are those that parasitize humans  Ascomycetes cause ringworm and athlete’s foot  Coccidioidomycosis produces tuberculosis like symptoms in lungs  Candida albicans normal on moist epithelia, grow to rapidly causes vaginal infections, diaper rash, and thrush

Practical Uses  Food  Flavors of cheese  Aspergillus used for citric acid in cola  Yeasts for breads, beer, and wine  Medicine  Antibiotic treatments  Penicillium used to produce penicillin  Saccharomyces used to study Parkinson’s and Huntington’s disease