Chapter 23 – The Fungi Domain - Eukarya Kindom - Fungi
Kingdom Fungi • Mycology – study of fungi; myco=fungus, -logy=study • More than 100,000 known species; • Nutrition – • Heterotrophic by absorption following secretion of enzymes; most saprotrophic • Some parasitic on living tissues of plant/animal • Some mutualists (symbionts) – with plant roots and algae • eukaryotic organisms; • both unicellular (yeasts) and but mostly multicellular (mushrooms) forms; • found in almost all habitats; free-living and parasitic forms represented
Fungal facts • Fungi perform important roles along with bacteria as decomposers within various ecosystems; they also cause a variety of plant and animal diseases • Commercial value of fungi includes role in the production of various cheeses; the role of yeast fermentation in wine-making, brewing, and baking; and the production of antibiotics (penicillin). Many mushrooms and truffles are edible.
Fungal Terminology • hypha - a single filament making up the body of a fungus • mycelium - the mass of filaments (hyphae) of which a fungus is composed; mycelium is the thallus (body) of most fungi • septa - divide fungal hyphae into "cells"; septa contain pores that allow intercellular communication including transfer of cytoplasm, ribosomes, mitochondria, and nuclei – septate hyphae • cell walls - composed of chitin (polymer of glucose); lack chloroplasts; energy reserve is glycogen • coenocytic fungi - cells fuse in certain fungi forming a continuous stream of cytoplasm and filaments containing many nuclei – nonseptate hyphae
Hyphae of fungi coenocytic
Fungal facts • Fungi secrete hydrolytic digestive enzymes and then acquire nutrients through absorption; • proteins and other compounds synthesized by the mycelium are transferred by cytoplasmic streaming to the tips of the hyphae; • a process that allows fungi to grow very rapidly
Reproduction of fungi • Fungi reproduce sexually or asexually; spores may be produced sexually or asexually; • In general, fungal sexual reproduction involves the following: • haploid hyphae → dikaryotic stage → diploid zygote ↑--------------------- meiosis---------------↓ spores
Fungal sexual reproduction, continued • During sexual reproduction, haploid hyphae from two different mating types ( + and - ) fuse. • If nuclei do not fuse immediately, the resulting hypha is dikaryotic (contains paired haploid nuclei, (n + n). • a. In some species, nuclei pair but do not fuse for days, months, or even years. • b. The nuclei continue to divide in such a way that every cell has at least one of each type of nucleus. • When the nuclei fuse, the resulting zygote undergoes meiotic cell division leading to spore formation. • Fungal spores germinate directly into haploid hyphae without embryological development.
Fungal Spore Formation • Spores are an adaptation to life on land and ensure that the species will be dispersed to new locations. • A sporeis a reproductive cell that can grow directly into a new organism. • Fungi produce spores both during sexual and asexual reproduction. • Although nonmotile, the spores are readily dispersed by wind.
Fungal asexual reproduction • Asexual reproduction can occur by three mechanisms: Production of spores by a single mycelium is the most common mechanism. Fragmentation is when a portion of a mycelium becomes separated and begins a life of its own. Budding is typical of yeasts; a small cell forms and gets pinched off as it grows to full size.
Survey of Major Fungal Phyla Phylum Zygomycota • 1. Phylum Zygomycota – the zygospore fungi - 600 species; group composed of coenocytic hyphae; reproduction by sporangium – produce spores Examples: Rhizopus stolonifera the common black, bread mold Also the mycorrhizal fungi (mycorrhizae) which form mutualistic associations with the root systems of various plants and help the plant with the uptake of water and nutrients (greater absorptive surface area); fungus benefits by receiving carbohydrates from the plant. Over 95% of vascular plants have mycorrhizae; some also belong to Ascomycota and Basidiomycota.
Phylum Ascomycota • 2. Phylum Ascomycota - 60,000 species; consist ofsingle cell (yeasts) to mycelium of septate hyphae; called "sac fungi" because of spore-producing saclike asci (sexual reproduction);. Usually asexual reproduction by producing spores called conidia. • The truffle (Tuber sp.) lives in association with oak and beech tree roots (mycorrhizal association); it can be inoculated with the fungus • a. yeasts - unicellular fungi capable of fermentation; usually reproduce asexually by budding Saccharomycescerevisiae - beer and wines (ethanol, CO2);bread rising (CO2) Candidaalbicans is the causative agent of human yeast infections and oral thrush;
Phylum Ascomycota • b. molds – helpful and harmful to humans • Stachybotryschartarum black mold “sick building” syndrome; • Aspergillus sp.-soy sauce by fermentation of soybeans; A. flavus – grows on grain seed and secretes carcinogenic toxin • Talaromyces (formerly Penicillium) – antibiotic penicillin • Athlete's fungus, ringworm (Tinea) • Fungal flu (Midwest) Histoplasma sp. – grows in mold and yeast forms in soil, associated w/ bird droppings-immune system/systemic illness • Ergot of rye - Clavicepspurpurea, produces lysergic acid; human disease ergotism • Chestnut blight - has virtually eliminated American chestnuts • Dutch elm disease - transmitted by bark beetles • Powdery mildews and leaf curl fungi impact leaves
Note: Phylum Deuteromycota now in Ascomycota • Phylum Deuteromycota - the "imperfect fungi" due to the absence of a sexual stage; includes Penicillium important in antibiotic and cheese production; and Tolypocladium the source of cyclosporine
Phylum Ascomycota Morels, Cup Fungi, and Flask Fungi (below, left-to-right)
Phylum Ascomycota • c. lichens - mutualistic (more-or-less) associations of an algae (Cyanobacteria) and a fungus (usually an Ascomycota, some Basidiomycota); • Three types of lichens are recognized. • a. Compact crustoselichens are often seen on bare rocks or tree bark. • b. Folioselichens are leaflike. • c. Fruticoselichensare shrublike.
a fruticose lichen - shrublike • Reindeer moss
Gray frosted rosette lichen (Physcia biziana) & orange sunburst lichenXanthoria) on bark at the south rim of the Grand Canyon, Arizona(both Ascomycota)
Phylum Basidiomycota • 3. Phylum Basidiomycota - 25,000 species; called "club fungi" due to the club-shaped basidium, a spore-producing structure found in this group - gives rise to basidiospores. • mushroom (basidiocarp) – tightly packed hyphae; cap, gills, stalk, rhizoids (small branching hyphae) • mushrooms and toadstools; shelf fungi, puffballs, stinkhorns, bird’s nest fungi, jelly fungi • many edible species including portabella and shitake are in this group. • the plant parasites wheat rusts and corn smuts • Smuts and rusts are club fungi that parasitize cereal crops (e.g., corn, wheat, oats, and rye) • Don’t form basidocarps, numerous spores resemble soot
Basidiomycota • Hygrocybe coccinea, Scarlet Hood mushroom
Basidiomycota Stropharia species from Washington State
Shelf fungus Lenzites betulina
Toothed fungi Hydnum repandum toothed fungi
Crust fungus Phanerochaete chrysorhizon
Coral fungi Clavulinopsis corallinorosacea Ramaria stricta
Amanitas – very poisonous Amanita muscaria Amanita pantherina var. pantherina