Fungi Instructor Thomas Carlson Fungi are more closely related to animals than plants Fungi and Animals Chitin in cell walls of fungi and in exoskeletons of invertebrates Flagella Store carbon by synthesizing glycogen polysaccharide Fungi Lectures Bio 1B Fall 2008 Plants Cellulose in cell walls Store carbon by synthesizing starch polysaccharide 1 2 Fungi have an absorptive lifestyle Nutrition Habit 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 Some are parasitic or mutualistic absorb nutrients from living plants animals humans Some are saprophytic absorb nutrients from dead decomposing plant and or animal tissue recycle nutrients back into the biosphere 3 4 Multicellular mycelium Fungi grow in two ways Figs 31 2 31 3 31 4 composed of filaments known as hyphae Mushrooms consist of densely packed hyphae multicellular mycelia e g mushrooms Hyphae Figs 31 2 31 3 31 4 long narrow tubular filaments optimizes surface area volume ratio which enhances absorption single celled yeasts baker s yeast Saccharomyces cerevisiae Fig 31 7 Candida albicans a commensal fungus living in and on humans that can be pathogenic in humans hyphae may be broken into compartments by septa that contain gaps which enables movement of materials between compartments 5 6 7 8 Extracellular digestion by saprophytic fungi 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 Fungi secrete digestive enzymes outside of their hyphae 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 9 Lignin and cellulose degrading fungi play important role in global carbon cycle 10 Concentration of fungal spores are at times comparable to pollen grains in air samples Spores fall on food source Lignin degradation germinate mycelium forms grows in direction of food when food source diminishes spores are produced hyphae excrete lignin peroxidase into extracellular environment breaks down dense lignin matrix around long strands of cellulose Cellulose digestion With adequate food sources mycelia can be large and long lived Cellulases excreted into extracellular environment breakdown cellulose 11 12 In Northwest USA a massive individual mycelium Mutualisms Both fungus and host plant derive benefit 1290 acres 6 5 square km hundreds of tons thousands of years old one of the largest most long lived organisms known Mycorrhizae 31 4b 36 5 37 12 common association between fungi land plant roots fungi make nitrogen and phosphorous available to plants fungi receive sugars other carbon sources from plant 13 14 Ectomycorrhizal Fungi EMF Fig 37 12a Dense network of hyphae around roots Found in almost all tree species in temperate boreal forests Basidiomycetes often form this type of association 15 16 Arbuscular mycorrhizal Fungi AMF Endomycorrhizae Ectomycorrhizal Fungi EMF Fig 31 15 37 12b Short growing season in temperate areas slow decomposition nitrogen remains tied up in dead tissues 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 17 Grow in cells of root tissue Found in 80 of all plant species Glomeromycetes fungi Supply plants with phosphorous Especially in grasslands forest in warm tropical habitats where the growing season is long and nitrogen is available 18 Lichens Fig 31 23 31 24 Results from the symbiotic association of a true fungus and either a cyanobacteria or a green alga Most fungi are ascomycetes some are basidiomyctes Live in tundras and on bare rock contribute to rock breakdown and soil formation Fungi provides protection to cyanobacteria or green algae Algae or cyanobacteria provide carbohydrate to fungus 19 20 Ascomycete Cordyceps fungus growing out of head of caterpillar Parasitism On Plants Fig 31 25 Parasitic fungi killed billions American chestnut American elm trees Dutch elm disease Corn smut fungal infection Tar spot on maple leaves 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 Humans get infected by inhaling fungal spores into their lungs 21 22 Evolution of Fungi Figs 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 23 24 25 Chytridiomycota Fig 31 11 31 12 26 Zygomycota Fig 31 13 only fungi group that are aquatic infections in frogs e g Batarachochytrium dendrobatidis epidemic infection in mountain yellow legged frogs in Sierra Nevada mountains of Califonia motile cells Most live in soil zygote with tough outer coat Some have mutualistic arbuscular mycorrhizal relationships gametes in sexual reproduction spores in asexual reproduction centrioles associated with nuclear membrane during cell division Some live on bread e g Rhizopus stolonifer 27 Zygomycota Reproduction Fig 31 13 Hyphae are haploid 28 Glomerulomycota Fig 31 11 Two different mating types become yoked together haploid nuclei fuse All form distinct types of endomycorrhizae called abruscular mycorrhizae diploid zygote is resistant to extreme conditions favorable conditions enable meiosis Tips of hyphae push into plant root cells and branch into treelike structures called arbuscules meiotic products produce haploid cells spores are released germinate and grow into new mycelia 29 30 Fungi in Ascomycota group Ascomycota sac fungi Fig 31 16 31 11 Fig 31 16 31 17 Lichen fungi e g Cladonia Usnea Claviceps purpurea ergot fungus parasitic on rye source for original LSD Morchella esculenta morel edible mushroom Fig 31 16 Tuber melanosporum truffle Fig 31 16 Candida albicans which can be a human pathogen Saccharomyces is used to brew beer and make bread Fig 31 7 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
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