Chapter 31 Fungi Characteristics Fungus feeding body is the mycelium o Made up of branching filamentous thread like Hyphae 31 2 Often unseen underground or within the host o Hyphae secret hydrolytic enzymes and acids This digests organic materials Simple organic molecules are absorbed Thus fungi are absorptive heterotrophs Hyphae are made of tubular cells like a network of pipes o Rigid cell walls with chitin also in insect exoskeletons o Multicellular septate or coenocytic hyphae Both allow rapid cytoplasmic streaming Septate thin dividing walls between cells Coenocytic all continuous o Rapid growth at hyphal tips toward new food no motile feeding cells o Huge total surface area for absorbption o Some specialized hyphae 31 4 Haustoria penetrate cell walls BUT NOT the membrane of host plants Some hyphae catch nematodes for the N Reproductive bodies make spores o Usually above ground and therefore what we notice Fairy rings 1 organism mycelium spread out reproduction at the most active places Some fungi are yeasts 31 7 o Unicellular o Live in water films or moist tissue Fungus Reproduction Spores n made in both sexual and asexual cycles o Dispensed by air and water to new resources Spores germinate if they land on food and water o Each grows into a new haploid mycelium Sexual cycles make no gametes o No genders instead plus or minus mating types o 3 steps to form the zygote Plasmogomy fusion of plus and minus hyphae Heterokaryotic stage hyphae with unfused haploid nuclei of both types Karyogomy fusion of haploid nuclei to form a zygote 2n o Plasmogomy and karyogomy are equivalent to fertilization in animals o Zygote 2n always does meiosis immediately after forming making genetically diverse spores n Fungi never have a multicellular 2n stage o Fig 31 5 KNOW for test Asexual cycles common 31 13 17 o Making genetically identical spores and mycelia Growths like this are called mold o Single cell yeasts bud off new daughter cell by mitosis o Fragments of mycelium can grow into a new individual Origin of Fungi Share unicellular flagellated ancestor with animals o Multicellularity evolved independently Land invasion o Oldest fungi fossils are about 460 mya terrestrial o Lichen like fossils date even older o Earliest plant roots also had mycorrhizae Phylogeny Aquatic Flagella o Chytrids Terrestrial No flagella o Zygomycestes o Glomeromycetes o Ascomycetes o Bassidiomycetes Importance of Fungi Fungi are Decomposers o Break down dead tissue including ligin Especially wood Only second to bacteria in importance o Damage property Dry rot wet rot mold and mildew Fungi are mutulaists o Mycorrhizae 37 13 Fungi living in close association with almost all plant roots Mycorrhizal fungi help plant absorb moisture and minerals Fungi gets sugars ect from the plant o Lichen 31 23 24 Fungi living in close associate with photosynthetic unicellular chlorophyte cyanobacteria Fungus gives frame work moisture and minerals Algae cyanobacteria give sugar Can reproduce as dual organisms via Soredia Key pioneer organisms on bare rock and harsh environments Create soil for plants which lead to food for animals o Fungus gardening ants 31 22 Leaf cutting ants provide food and are to fungus wicch the eat Fungi are pathogens o Infecting plants Attack trees landscape plants crops Rusts and smuts Ergot on barley and rye ergotism LSD 31 25 Various molds Aspergillus mold in peanuts Pink ear mold in corn o Infecting animals Chytria causing a huge decline in amphibian populations Zombie ants caused by Ascomycete o Humans Mycosis is infection due to fungus Some are very serious and difficult to treat Ex recent meningitis from steroid shots Many are common and treatable Ex ringworm athlete s foot jock itch and vaginal yeast infection Benefit medicine and research o Source of antibiotics and other drugs Ex penicillin 31 27 o Genetic reseach and biotechnology Ex Neurospora a research model organism yeasts Fungi and food o Humans eat it o Truffles o Yeast fermentation CO2 for rising bread Ethyl alcohol in beer and wine o Molds used in food processing Ex Beer cheese soy sauce Poisonous fungi o Many mushrooms are deadly o Never eat wild fungi Largest organisms are fungi
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