Chapter 31 Monday March 28 2016 1 44 PM Chapter 31 Fungi Characteristics of Fungi Most fungi are multicellular and terrestrial o Ex Bread mold shelf fungus mushrooms cup fungi puff balls o But many Chytrids are aquatic with hyphae true alt of gen o And some fungi are unicellular yeasts Live on water films most tissue of a host that is infected Ex Brewer s yeast Ex Infective form of vaginal yeast The main fungus body is a mycelium o A network of filamentous thread like hyphae singular hypha o Often unseen underground or within hosts o Feeds and grows often enormous o Fungi are made of individual threads that are always growing Hyphae are made of tubular cells o Rigid cell walls with chitin o Septate or coenocytic hyphae Septate hyphae has septum inside that divide it with pores for nuclei to go through Coenocytic have cell wall and nuclei with no septum Both allow rapid cytoplasmic streaming movement of material by actin b Rapid growth release of enzymes at tips Hyphae feed by absorbing simple organic compounds o Thus fungi are absorptive heterotrophs o Most secrete hydrolytic enzymes and acids o o o This digests organic materials Hydrolytic hydrolysis breaking down of water Macromolecule polyprotein Acids denature proteins Rapid growth at hyphal tips toward new food no motile feeding cells Huge total surface area for absorption Cytoplasmic streaming toward the tip Some specialized hyphae Haustoria penetrate cell walls of host plant without killing cell If it is a parasitic cell it will live off the food supply of the plant If symbiotic it exchanges organic material with the plant Host plasma membrane not penetrated Some hyphae catch nematodes for nitrogen The wood decaying fungus needs the nitrogen from this worm s proteins Reproductive bodies emerge from a mycelium to make spores Fungus Reproduction o Summary for fungi excluding Chytrids Spores haploid n are made in both sexual and asexual cycles o Disperse by air water to new sources Spores made asexually at tips of hyphae Spores from sexual cycle Major distribution stage of the fungi o Spores germinate on food source o Each grows into a new haploid n mycelium Asexual reproduction is common o Mitosis makes genetically identical spores that grow new mycelia Zygomycete asexual reproduction Ascomycete asexual reproduction Mycelia are haploid for the most part Spores are all haploid so grow into haploid mycelia Growths like this are called mold o By fragmentation bits of mycelium can grow into new individual o In single cell yeasts by budding off daughter cells by mitosis Parent cell connected to bud Buds out the new individual Sexual cycles make no male female gametes o No genders instead positive or mating types o Three steps to form zygote Plasmogamy fusion of haploid or hyphae Gamy marry Plasmo cytoplasm Fusion of cytoplasm Grow toward together until the cell walls touch so cytoplasm can actually intermix Heterokaryotic stage hyphae with unfused haploid nuclei of both types Sharing the same cytoplasm Karyogamy fusion of haploid nuclei to form zygote 2n Karyo nucleus Gamy marry o Zygote 2n always does meiosis making genetically diverse spores n Never a multicellular 2n stage potential of survival in a new environment is greater Generalized life cycles o Learn what processes in comparison to generalized life cycle o Mycelia haploid o Heterokaryotic n n stage Start off as haploid mycelium encounter another mating type Process of plasmogamy into heterokaryotic stage n n of two different types two because separated into two different Karyogamy in formation of zygote Zygote may last for a while or in dormant stage Reduce back down to haploid stage through meiosis o Karyogamy only forms on the gills where basidia are Origin and Phylogeny of Fungi Origin of Fungi o Fungi are Opisthokonts Unicellular flagellated aquatic ancestor Multicellularity evolved independently Chytrids many are aquatic with flagellated zoospores The rest are terrestrial o Fungi origins tied to land invasion Oldest fungi fossils 460 million years old terrestrial Earliest plants also had mycorrhizae Fungus Phylogeny o Chytrids Basal fungus group Aquatic decomposers or parasites Flagellated zoospore o o o o Chitin in cell wall Dramatic impact on killing amphibians Zygomycetes terrestrial or in terrestrial hosts Sexual cycle makes a resistant zygosporangium Glomeromycetes terrestrial or in terrestrial hosts Mutualistic arbuscular mycorrhizae Associated with plant root tissue Ascomycetes terrestrial or in terrestrial hosts Sexual spores within saclike ascus plural asci Ascospores located in a single fruiting body known as an ascocarp most diverse group of fungi Contains lichens Where karyogamy occurs Where zygote is formed goes through meiosis to make sexual spores Within fruiting body called ascocarp Ex Cup fungus Basidiomycetes terrestrial or in terrestrial hosts Sexual spores within club like basidium Ex Mushrooms shelf fungus puff balls Importance of Fungi Fungi are Decomposers o Break down dead tissues including lignin Only second to bacteria in importance shelf fungus is feeding on dead stump basidiomycete Many bacteria and fungi are great at decomposing cellulose but most bacteria cannot break down lignin Lignin polymer durable molecule that makes wood hard Fungi Damage Property o Dry rot o Wet rot o Mold o Mildew Fungi are Mutualists o Mycorrhizae Fungi living in close association with almost all plant roots Ectomycorrhizae outside penetrate through around root cells Endomycorrhizae or arbuscular mycorrhizae penetrating fungal hyphae haustorium within into the cells Mycorrhizal fungi help plants absorb moisture and minerals Fungus gets sugars etc from plant o Lichens Fungi living in close association with photosynthetic unicellular chlorophyte or cyanobacteria photosynthetic algae or cyanobacteria Fungus gives framework moisture minerals Algae cyanobacteria gives sugar Can reproduce as dual organism via soredia Key pioneers on bare rock and harsh environments Create soil for plants food for animals Fungi are Pathogens o Infecting plants Attack trees landscape plants crops E g rusts and smuts means it has the particular fungal E g ergot ergotism LSD Salem Witch Trials Rye fungus the source of LSD cause hallucinations Various molds o Infecting many animals Ex Killed by Chytrid wiping out amphibians worldwide Chytrids can kill amphibians currently trying to figure Ex Zombie ants killed by ascomycete o Infecting humans Mycosis infection due to fungus Some very