Professor Thomas Carlson Fungi Lectures Bio 1B Fall 2007 1 Fungi 2 Nutrition Habit Fungi are more closely related to animals than plants Fungi and Animals Chitin in cell walls Flagella Store carbon by synthesizing glycogen polysaccharide Plants Cellulose in cell walls Store carbon by synthesizing starch polysaccharide 3 Fungi have an absorptive lifestyle Land Plants photosynthesis Fungi absorb nutrients from living or dead organisms Animals absorb nutrients from living or dead organisms Land Plants do not live on or in humans Fungi may live on and in humans 4 Fungi grow in two ways Some are parasitic or mutualistic absorb nutrients from living plants animals humans multicellular mycelia e g mushrooms Some are saprophytic absorb nutrients from dead decomposing plant Fig 31 1 and or animal tissue recycle nutrients back into the biosphere single celled yeasts baker s yeast Saccharomyces cerevisiae Candida albicans can be pathogenic in humans 5 6 Multicellular mycelium Figs 31 2 31 3 31 4 composed of filaments known as hyphae Mushrooms consist of densely packed hyphae Hyphae Figs 31 2 31 3 31 4 long narrow tubular filaments optimizes surface area volume ratio which enhances absorption hyphae may be broken into compartments by septa that contain gaps which enables movement of materials between compartments 7 8 Saprophytic fungi Saprophytic fungi are decomposers that reverse biosynthesis by breaking down plant and animal tissue and recycling nutrients back into the biosphere Some fungal organisms can digest wood Fig 31 1 9 10 Lignin and cellulose degrading fungi play important role in global carbon cycle Extracellular digestion by saprophytic fungi Fungi secrete digestive enzymes outside of their hyphae Lignin degradation hyphae excrete lignin peroxidase into extracellular environment breaks down dense lignin matrix around long strands of cellulose breakdown cellulose starch lignin proteins RNA into smaller compounds e g sugars amino acids nucleic acids able to diffuse across the cell membrane into the hyphae Cellulose digestion Cellulases excreted into extracellular environment breakdown cellulose 11 12 Concentration of fungal spores are at times comparable to pollen grains in air samples In Northwest USA a massive individual mycelium Spores fall on food source germinate mycelium forms grows in direction of food when food source diminishes spores are produced 1290 acres 6 5 square km hundreds of tons thousands of years old one of the largest most long lived organisms known With adequate food sources mycelia can be large and long lived 13 14 15 16 Mutualisms Both fungus and host plant derive benefit Mycorrhizae Fig 31 4b 31 15 36 9 36 10 common association between fungi land plant roots fungi make nitrogen and phosphorous available to plants fungi receive sugars other carbon sources from plant Ectomycorrhizal Fungi EMF Ectomycorrhizal Fungi EMF Short growing season in temperate areas Dense network of hyphae around roots slow decomposition nitrogen remains tied up in dead tissues Found in almost all tree species in temperate boreal forests EMF releases peptidases that cleave peptide bonds of amino acids nitrogen is released absorbed by the fungal hypha transported close to tree roots absorbed by plant Basidiomycetes form this type of association 17 18 Arbuscular mycorrhizal Fungi AMF Endomycorrhizae Lichens Fig 31 23 31 24 Results from the symbiotic association of a true fungus and either a cyanobacteria or a green alga Fig 31 15 Most fungi are ascomycetes some are basidiomyctes Grow in cells of root tissue Found in 80 of all plant species Commonly are Glomeromycetes fungi Supply plants with phosphorous Especially in grasslands forest in warm tropical habitats where the growing season is long and nitrogen is available Live in tundras and on bare rock contribute to rock breakdown and soil formation Fungi provides protection to cyanobacteria or green algae 19 Algae or cyanobacteria provide carbohydrate to fungus 20 Parasitism On Plants Fig 31 25 Parasitic fungi killed billions American chestnut American elm trees Dutch elm disease Corn smut fungal infection Ergot infection Claviceps pupurea in rye grains On Animals Chytridiomycota species infect kill frogs Cordyceps fungi infects certain caterpillars On Humans Coccidiodomycosis Valley Fever causes fungal infection in humans living in the central valley of California 21 22 23 24 Evolution of Fungi Figs 31 9 31 11 Chytridiomycota and Zygomycetes branched off very close together in time and are the earliest known fungal groups Glomeromycetes form endomycorrhizae called arbuscular mycorrhizae Basidiomycota and Ascomycota represent later more derived groups 25 26 Chytridiomycota Fig 31 10 Only fungi group that are aquatic infections in frogs motile cells gametes in sexual reproduction spores in asexual reproduction 27 Zygomycota Fig 31 12 centrioles associated with nuclear membrane during cell division 28 Zygomycota Reproduction Fig 31 12 Two different mating types become yoked together Most live in soil haploid nuclei fuse zygote with tough outer coat diploid zygote is resistant to extreme conditions Some have mutualistic arbuscular mycorrhizal relationships favorable conditions enable meiosis meiotic products produce haploid cells Some live on bread e g Rhizopus stolonifer Hyphae are haploid spores are released germinate and grow into new mycelia 29 30 Ascomycota sac fungi Glomerulomycota Fig 31 16 31 17 Some are microscopic yeast e g Candida albicans All form distinct types of endomycorrhizae called abruscular mycorrhizae Tips of hyphae push into plant root cells and branch inot treelike structures called arbuscules Some have sac like spore producing structures and multicellular mycelia Some have dikaryotic stage like Basidiomycota Similar reproductive cycle as Basidiomycota except that meiosis takes place in the ascus sac Fig 31 17 31 32 Fungi in Ascomycota group Fig 31 16 Lichen fungi e g Cladonia Usnea Claviceps purpurea ergot fungus parasitic on rye source for original LSD Tuber melanosporum truffle Fig 31 16c Candida albicans which can be a human pathogen Saccharomyces which is used to brew beer and make bread Aspergillus tamari used to ferment soybeans to make soy ste soy sauce tamari Aspergillus oryzae used to brew sake in Japan Penicillium species and other genera to produce antibiotics Penicillium roquefortii used to make Roquefort cheese Penicillium camenbertii used to make camenber cheese 33 34 Basidiomycota Figs 31 18 31 19 31
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