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Fungi Soil Soil I. Classification, morphology.. II. Fungi distribution in soil III. Survival and propagation IV. Important roles of fungi in soil 1. Organic matter degradation 2. Importance in soil foodwebs 3. Parasites and pathogens 4. production of mycotoxins 5. Mutualistic associations 5. Soil aggregation IV. Application of soil fungi 1. Fermentation 2. production of antibiotics 3. Biological control 4. Bioremediation Reading: Textbook: Sylvia et al., 2004. Chapter 6, pages 141-161. Eukaryotes Fungi Eukaryote Nuclearmembrane Multiplechromosomes Mitochondria,organelles Polysaccharidetypewall(cellulose, chitin) Twotypesofribosomes(80S,70S) Multicellularanddifferentiated Sexualreproduction Cells>5 mindiameter Structuraldiversity From Coyne, Soil Microbiology Bacteria Prokaryote Nonuclearmembrane Singlechromosome Fewinternalstructures Peptidoglycanwalls 70Sribosomesonly Usuallyunicellular Asexualreproduction Cells<5 mindiameter Metabolicdiversity Heterotrophs Saprotroph Parasite Symbiont Hyphae Filaments: 3-10 m in Mycelium Nature 356(2) 428-431, 1992 2003: Armillaria ostoyae, Oregon - 0.15 km2 (37 acres) - 1500 years old - 8.9 km2 (2,200 acres) - 2000-8650 years old Filamentous Fungi Single-cell yeasts Fungal cell wall Eukaryotes Heterotrophs Almost all aerobic 80.000 species described but much more exist Fungal distribution Organism Plantroots Fungi Bacteria Actinomycetes Protozoa Nematodes Earthworms Biomass(kgper hectare) 20,00090,000 2,500 1,0002,000 02,000 0500 0200 02,500 Relative contribution of soil organisms to the biomass of a temperate grassland soil Fungal distribution Determined by: - Availability of organic C (most are saprobes) - Vegetation composition - pH (tolerant to acid pH) - Temperature (mesophile) - Water - Oxygen (most are strictly aerobes in top 15 cm of soils) Fungal distribution: mutualism Endophytic association Neotyphodium coenophialum in Festuca arundinacea Mycorrhizal association (see next lecture) Survival and propagation - sexual and asexual spores - survival from weeks to years in soil conidia: asexual spores ascospores: result of sexual fusion sclerotia: aggregated hyphae, easily dispersed Survival and propagation Active dispersion Fairy rings Survival and propagation 2.5 m Pilobolus (ballistospores) Ascomycetes Survival and propagation ascus Max 0.5 m ascospores Ascomycetes Survival and propagation spore basidia 0.5-1 mm Basidiomycetes Survival and propagation Passive dispersion by wind or water Earthstar Puffball spore dispersal dry wet Survival and propagation Passive dispersion by animals Truffle Stinkhorn From Van Elsas et al., Modern Soil Microbiology, 2007 1. Organic matter decay Role of Fungi in soils Role of Fungi in soils 2. Importance in soil foodwebs Food source for invertebrates Predators of nematodes SEM of a nematode caught in the constricting rings of Arthrobotrys anchonia Adhesive net nematodes by trapped the adhesive nets of the predatory fungus Arthrobotrys oligospora Role of Fungi in soils 3. Parasites and pathogens 70% of crop diseases are caused by fungi Sudden Oak Death (Phytophthora ramorum) From Van Elsas et al., Modern Soil Microbiology, 2007 Role of Fungi in soils 4. Production of mycotoxins (reported as early as 1861) Poisonous mushrooms responsible for 95 % of the fatal cases of mushroom poisoning throughout the world Amanita muscaria Amanita phalloides Role of Fungi in soils 4. Production of mycotoxins (reported as early as 1861) Ergot (Claviceps purpurea) Ergotism (St Anthonys fire) Role of Fungi in soils 5. Mutualistic associations Mycorrhizae (cf next lecture) Lichens Role of Fungi in soils 6. Enhanced soil aggregation Applications of soil Fungi 1. Fermentation (yeasts) Penicillium species yeasts Saccharomyces cerevisiae and S. carlsbergensis Aspergillus oryzae Applications of soil Fungi 2. Production of antibiotics Penicillin discovered in 1928 by Alexander Fleming Isolated from a mold, Penicillium notatum First drug against syphilis and Staphylococcus 1945 Nobel prize Staphylococcus aureus Penicillium Applications of soil Fungi 3. Biological control About 20 fungal products sold commercially Competition for space and for nutrients, predation and antibiotics Myrothecium verrucaria as biocontrol of weed species Applications of soil Fungi 3. Biological control Fungi to Control Plant Diseases: Root rot of Conifers Root rot of pine caused by the bracket fungus Heterobasidium annosum Phlebiopsis gigantea prevents invasion by the pathogen Heterobasidium annosum Applications of soil Fungi 3. Biological control Fungi to Control Plant Diseases: Post-harvest rot of citrus fruits Fruit rot of citrus showing the effectiveness of biocontrol with Pichia guillermondii (U.S.-7) Applications of soil Fungi 3. Biological control Biocontrol of insects: Control of cabbage loopers with Noumorea rileyi Control of coakroach with Metarrhizium body cavity full of spores Applications of soil Fungi 3. Biological control Biocontrol of Nematodes: a) Nematode-trapping fungi: Arthrobotrys irregularis, Dactylella spp. Monacrosporium spp. Dactylella drechsleri Monacrosporium robustum Anthrobotrys dactyloides Applications of soil Fungi 3. Biological control Biocontrol of Nematodes: b) Endoparasitic fungi: Drechmeria coniospora, Catenary anguillulae, Hirsutella rhossiliensis sinuous fungal hyphae inside the nematode conidia Drechmeria coniospora Applications of soil Fungi 3. Biological control Biocontrol of Nematodes: c) Parasitic fungi attacking sedentary stages of nematodes: Pochonia chlamydosporia, Paecilomyces lilacinus P. chlamydosporia infected Meloidogyne incognita egg Applications of soil Fungi 4. Bioremediation - White-rot fungi - PAHs - Chlorophenols - Nitrotoluenes - Polychlorinated biphenyls - Azo dyes Applications of soil Fungi 5. They are delicious ... View Full Document

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