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FUNGI. What fungi are like. general multicellular eukaryotes varied structure mode of nutrition saprotrophic decomposers parasitic plants (enter through the stomates) animals (ring worm, yeast, athlete's foot) symbiotic. most fungi are filamentous
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What fungi are like • general • multicellular eukaryotes • varied structure • mode of nutrition • saprotrophic decomposers • parasitic • plants (enter through the stomates) • animals (ring worm, yeast, athlete's foot) • symbiotic
most fungi are filamentous • mycelium made up of many hyphae Fig. 17.16A • hyphae give the mycelium a large surface area per volume • cell wall made of chitin • fungi move toward a food source by growing toward it • hyphae can be nonseptate or septate m 381
most fungi produce spores • sexual reproduction • hypha containing paired haploid nuclei are n + n or dikaryotic (may remain like this for some time) • when the nuclei fuse the zygote undergoes meiosis prior to spore formation • fungal spores germinate directly into haploid hyphae • spores are wind dispersed • reproduction by budding • reproduction by fragmentation
How fungi are classified • 1. zygospore fungi from zygospores (division Zygomycota) (from lab) • black bread mold (Rhizopus) • m 382, Raven
2. sac fungi from ascospores (division Ascomycota) Raven • nutrition • decompose materials containing cellulose, lignin, or collagen • examples • decomposers: morels, truffles, cup fungi • parasitic: powdery mildews, leaf curl fungi, chestnut blight and Dutch elm, and ergot from rye
reproduction (sexual) m 383 • composed of septate hyphae • ascus (fingerlike sac that develops during sexual reproduction) • ascus producing hyphae remain dikaryotic except in the walled off portion that becomes the ascus where nuclear fusion, meiosis and ascospore formation take place • each ascus contains 8 haploid nuclei and produce 8 ascospores • wind dispersed
reproduction (asexual) • the norm • forms spores called conidiospores or conidia • conidia develop directly on the tips of modified aerial hyphae • there are no sporangia in ascomycetes • wind dispersed
3. yeasts (single cells) 2n • reproduce asexually by budding • reproduce sexually • when food supply runs out • forms asci and ascospores 1n • ascospores from two different mating types can fuse • diploid cell is formed and reproduces asexually before meiosis occurs and ascospores are produced again • haploid ascospores function directly as new yeast cells
uses • fermentation to ---> wine, bear • leavening agent that causes bread to rise • material of choice in genetic engineering
4. club fungi have basidiospores (division Basidiomycota) • general Fig. 17.17 p 361 • septate hyphae • familiar mushrooms growing in lawns • shelf or bracket fungi found on dead trees • less well known puffballs, bird's nest fungi, stink-horns • these structures are called basidiocarps and contain the basidia which make the basidiospores • wind dispersed
reproduction m 384 • usually sexual • monokaryotic (n) hyphae of two different mating types meet • form a dikaryotic (n + n) mycelium • mycelium continues its existence year after year (100 + years) • produce basidiocarp (mushroom) in ever increasing circles (fairy ring) • produce basidia where nuclear fusion, meiosis, and spore production occur • basidia has four projections into which cytoplasm and a haploid nucleus enter as the basidiospore forms
5. smuts and rusts are parasites • parasitize cereal crops such as corn, wheat, oats, and rye • life cycle of rusts often requires two different plant host species • difficult to control because rust can mutate to cause infection again • ergot on rye
6. imperfect fungi (division Deuteromycota) • reproduce asexually only (will see in lab) • called imperfect because they have no sexual stage seen as yet • uses • Penicillium - antibiotic • other species give Roquefort and Camembert cheeses their aroma and flavor • conidiospores in blue cheese give it its bluish streaks • cyclosporine an immuneo suppressant given after organ transplant • Aspergillus used to produce soy sauce by fermentation of soybeans, citrate and gallate
7. symbiotic fungi Fig. 17.18 p 362 • lichens (fungus plus an algae) m 385 • reproduce asexually • live in extreme conditions and contribute to the formation of soil
8. mycorrhizae are "fungus roots" • allow the plant to grow in mineral deficient soil • truffles are now cultivated by inoculating the roots of seedlings with the proper mycelium • truffles grow near oak and beech trees • many trees have companion mycorrhizae needed for good growth mauseth
