Fungi
Kingdom: Fungi (Eumycota) Kingdom: Fungi (Eumycota) • Sphongos (Greek: ): “spongy” ☛ Fungus (Latin): “mushroom” Fungal mycelium (body) is comprised of many hyphae (tubular filaments) • Mycos (Greek): “mushroom” • Mycology: the study of fungi Reproductive structure • Eukaryotic Hyphae • Multicellular (most) with limited differentiation
• Chitinous cell walls Spore-producing structures • ~100,000 named species
§ ~ a third with unclear taxonomy 60 μm • Heterotrophic with external digestion
• Haploid life history Mycelium (a mass of hyphae) Fig. 31.2
Fungal Cell
Kingdom: Fungi Structurally similar to Hyphae are septate or coenocytic plant cell • Large central vacuole • Cell wall • But primarily of chitin rather than cellulose • [No plastids] But biochemically & genetically more similar to animal cell
Hypha structure & growth Growth tip: Kingdom: Fungi • Mitosis ® divide nuclei • Vesicles accumulate at apex • Add new membrane and wall Heterotrophic • Osmotic uptake of water ® cell swells • Wall structure ® linear hypertrophy Secrete exoenzymes for external digestion • New septa form Absorb nutrients from environment Usually store fuel as glycogen (like animals) rather than starch (like plants) Most are saprobic Major decomposers Many are parasitic Many are mutualistic symbionts Mature cells with larger vacuoles Some are predatory! New cells rich in mitochondria
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Saprobic Fungi Symbiotic Fungi
Penicillium
1.5 µm • Present in many symbiotic (incl. parasitic) species • Hyphae penetrate soil or decaying tissues • Specialized branches off of hyphae • Erect sporangia to disperse spores • Note: penetrate cell wall, but not plasma membrane
Predatory Fungi Haploid Life History Key
Haploid (n) Heterokaryotic (unfused nuclei from different parents) Diploid (2n) KARYOGAMY (fusion of nuclei)
SEXUAL REPRODUCTION Zygote Mycelium
Digestive hyphae have removed all the worm tissue from this empty cuticle General Lifecycle of Fungus MEIOSIS GERMINATION • Only zygote is diploid • Hyphae specialized into adhesive nets or Spore-producing constricting slip-rings • Zygote immediately undergoes meiosis structures to form haploid daughter cells Spores • Prey are nematodes (soil round worms) - usually as spores (meiospores) • Source of protein to supplement calories obtained from decomposing cellulose Fig. 31.5
Plasmogamy & karyogamy Haploid Life History Haploid Life History may be separated by Key Key hours to decades!
Haploid (n) Haploid (n) Heterokaryotic Heterokaryotic Heterokaryotic stage (unfused nuclei from PLASMOGAMY (unfused nuclei from PLASMOGAMY different parents) (fusion of cytoplasm) different parents) (fusion of cytoplasm) Diploid (2n) Diploid (2n) KARYOGAMY KARYOGAMY (fusion of nuclei) (fusion of nuclei)
SEXUAL SEXUAL REPRODUCTION Zygote REPRODUCTION Zygote Mycelium Mycelium
General Lifecycle of Fungus MEIOSIS General Lifecycle of Fungus MEIOSIS GERMINATION GERMINATION • Haploid spores form haploid hyphae * Mating divided into two steps Spore-producing Spore-producing • May mate with haploid hyphae from structures 1. Plasmogamy: fusion of plasma membranes structures another mycelium Spores • Produces heterokaryotic cell Spores • Same species, but different mating type • Divide to form heterokaryotic hyphae • Prevent mating with its own hyphae 2. Karyogamy: fusion of dikaryotic nuclei Fig. 31.5 Fig. 31.5 • Attracted by pheromones • Produce diploid zygote
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Haploid Life History Key Fungal Haploid (n) Heterokaryotic Heterokaryotic stage (unfused nuclei from PLASMOGAMY Phyla different parents) (fusion of cytoplasm) Diploid (2n) KARYOGAMY (Divisions) (fusion of nuclei) Spore-producing structures SEXUAL REPRODUCTION Zygote ASEXUAL Mycelium REPRODUCTION Spores
MEIOSIS GERMINATION GERMINATION Spore-producing structures General Lifecycle of Fungus Spores • Most fungi can also produce spores asexually (conidiospores) • (Many only produce spores asexually) Fig. 31.5
Zygomycota Zygomycota Fig. 31.12 • >1,000 spp.
Hyphae are coenocytic
Rhizopus sp. Rhizopus sp.
Zygomycota
Zone of Mycelium #1 Mycelium #1 & Asexual Mycelium #2 sporangia from mating – Mycelium #1 zygosporangia formation
Asexual sporangia from fused hyphae zygosporangium Mycelium #2 Mycelium #2
Rhizopus sp. Rhizopus sp.
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Ascomycota (sac fungi) Ascomycota (sac fungi)
Fig. 31.16
• >65,000 spp.
Cultures of soil ascomycetes
Hyphae are usually septate & haploid
Ascomycota (sac fungi) Basidiomycota (club fungi)
Fig. 31.18
Yeasts — • Single-celled ascomycetes
Mushroom
Hyphae are usually septate & dikaryotic
Basidiomycota (club fungi) Basidiomycota (club fungi)
~30,000 spp. Fruiting Bodies
Mushroom
Shelf Fungus
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“Fairy Rings” Spores Basidium
Transient fruiting bodies (basiocarps) where the periphery of one mycelium encounters & mates with Mushroom Gill surrounding mycelia.
Ecological Importance Ecological Importance Decomposers Able to decompose usually nondigestible polymers, Cause of disease: in animals (mycosis) e.g., cellulose, lignin, waxes, chitin, keratin, etc.
Yellow-legged frogs killed by chytrid infection
Athlete’s foot
Dermatophytosis (“ringworm”) Entamapathogenic fungus
Ecological Importance Ecological Importance Cause of disease: in plants Mutualistic Endophytic (within plants) Fungi ~30% of known fungal species are plant pathogens Found within the cell walls of nearly all plants, esp. in leaves. • Resistance to osmotic or temp stress • Produce toxins against consumers, esp. insects • Provide pathogen resistance Soil Endophyte Plant # New Temp. (Curvularia) Mass (g) Shoots + or – Results Endophyte not present;E– pathogen16.2 present (E−P+)32 30Both°C endophyte and pathogen present (E+P+) E+ 22.8 60 30 15 35°C E– 21.7 43 E+ 28.4 60 (b) Tar spot 20 10 fungus 40°C E– 08.8 10 E+ 22.2 37 on maple 10 5 Leaf mortality (%) E– 00.0 00 leaves Without endophytes 45°C Leaf area damaged (%) R. S.0 Redman et al., ThermotoleranceE+ generated15.10 by plant/fungal24 (a) Corn smut on corn symbiosis, EScience−P+ 298:E 1581+P+ (2002). E−P+ E+P+ With endophytes (c) Ergots on rye
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Ecological Importance Mycorrhizae • Decompose organic matter in soil Symbiotic relationships: mycorrhizae – Free up inorganic nitrogen & phosphorus compounds • Produce organic acids – Dissolve minerals from soil particles • Increase surface area to absorb water & inorganic nutrients
Mycorrhizae Ecological Importance Ectomycorrhiza & Endomycorrhiza
Rhizosphere: special root environment Symbiotic relationships: lichens • Roots secrete substances - • stimulate germination of mycorrizzal spores & attract growing mycorrizzal hyphae • Mycorrizza secrete substances - • stimulate growth of root tips • Mycorrizza secrete volatile organics - • stimulate growth of beneficial soil bacteria
Symbiotic relationships: lichens Human Uses
Food
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Human Uses Human Uses Food Processing Food Death cap, Amanita phalloides Warning: >50% of mushroom poisonings
Edible & poisonous Destroying angel, A. bisporiga varieties are difficult Even more deadly, but rarer to distinguish! Esp. genus Amanita
Fly agaric, A. muscaria Insecticidal & hallucinogenic
Human Uses – Myco-Pharmaceuticals Human Uses – Myco-Pharmaceuticals Psycho-active mushrooms • psilocybin / psilocin (serotonin analogs) Antibiotics • adrenalin-like rush Zone of • visual/auditory hallucinations inhibited Penicillium • Mesoamerican growth mushroom stones
Bacteria (Staphylococcus)
• Psilocybe zapotecorum. Jalisco, Mexico
Human Uses – Myco-Pharmaceuticals Human Uses Statins Bioremediation (Mycoremediation) • Lower blood cholesterol Clean up contaminated environments • Decompose organic toxins – petroleum, pesticides, plastics, etc. • Accumulate inorganic toxins – heavy metals, incl. radioactive wastes
• Lovastatin from Aspergillus terreus and Pleurotus ostreatus (oyster Oyster mushrooms used to clean up mushroom) 2007 fuel oil spill in San Francisco Bay
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