*Chapter 31Monday, March 28, 20161:44 PM Chapter 31 - Fungi Characteristics of Fungi-Most fungi are multicellular and terrestrialoEx. Bread mold, shelf fungus, mushrooms, cup fungi, puff ballsoBut many Chytrids are aquatic (with hyphae, true alt. of gen.)oAnd some fungi are unicellular yeasts-Live on water films, most tissue (of a host that is infected)Ex. Brewer's yeastEx. Infective form of vaginal yeast-The main fungus body is a myceliumoA network of filamentous (thread-like) hyphae (singular hypha)oOften unseen: underground or within hostsoFeeds and grows; often enormousoFungi are made of individual threads that are always growing-Hyphae are made of tubular cellsoRigid cell walls with chitinoSeptate 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 septumBoth allow rapid cytoplasmic streaming (movement of material by actin)b. Rapid growth, release of enzymes attips-Hyphae feed by absorbing simple organic compoundsoThus fungi are absorptive heterotrophsoMost secrete hydrolytic enzymes and acids-This digests organic materialsHydrolytic - hydrolysis = breaking down of waterMacromolecule - polyproteinAcids - denature proteinsoRapid growth at hyphal tips toward new food (no motile feeding cells)oHuge total surface area for absorption-Cytoplasmic streaming toward the tipoSome 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 penetratedSome hyphae "catch" nematodes fornitrogen-The wood-decaying fungus needs the nitrogen from this worm's proteins-Reproductive bodies emerge from a mycelium to make spores Fungus ReproductionoSummary for fungi excluding Chytrids-Spores (haploid, n) are made in both sexual and asexual cyclesoDisperse by air/water to new sources-Spores made asexually at tips of hyphae-Spores from sexual cycle-Major distribution stage of the fungioSpores germinate on food sourceoEach grows into a new haploid (n) mycelium-Asexual reproduction is commonoMitosis 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"oBy fragmentation: bits of mycelium can grow into new individualoIn 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 gametesoNo genders; instead, positive (+) or (-) mating types oThree 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"oZygote (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:oLearn what processes in comparison to generalized life cycleoMycelia - haploidoHeterokaryotic - (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 meiosisoKaryogamy only forms on the gills where basidia are Origin and Phylogeny of Fungi-Origin of FungioFungi are Opisthokonts-Unicellular, flagellated, aquatic ancestorMulticellularity evolved independentlyChytrids - many are aquatic with flagellated zoosporesThe rest are terrestrialoFungi origins tied to land invasion-Oldest fungi fossils ~460 million years old (terrestrial)-Earliest plants also had mycorrhizae-Fungus PhylogenyoChytrids-Basal fungus group-Aquatic decomposers or parasites-Flagellated zoosporeChitin in cell wallDramatic impact on killing amphibiansoZygomycetes (terrestrial or in terrestrial hosts)-Sexual cycle makes a resistant zygosporangiumoGlomeromycetes (terrestrial or in terrestrial hosts)-Mutualistic arbuscular mycorrhizaeAssociated with plant root tissueoAscomycetes (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 fungusoBasidiomycetes (terrestrial or in terrestrial hosts)-Sexual spores within club-like basidium-Ex. Mushrooms, shelf fungus, puff balls Importance of Fungi-Fungi are DecomposersoBreak 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 Propertyo"Dry rot"o"Wet rot"o"Mold"o"Mildew"-Fungi are MutualistsoMycorrhizae-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 plantoLichens-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 PathogensoInfecting 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 moldsoInfecting many animals-Ex. Killed by Chytrid, wiping out