Chapter 24

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<ul><li> 1. 1Chapter 24Lecture OutlineSee separate PowerPoint slides for all figures and tables pre-insertedinto PowerPoint without notes.Copyright McGraw-Hill Education. Permission required for reproduction or display.</li></ul> <p> 2. A 460 million year old fossil fungus one of the oldest known2 3. 3Chapter 24FungiChapter Outline: Evolutionary Relationships of the Kingdom Fungi Fungal Bodies and Feeding Fungal Asexual and Sexual Reproduction The Importance of Fungi in Ecology and Medicine Biotechnological Applications of Fungi 4. Eukaryote supergroup Opisthokonta Includes certain protists, Kingdom Animalia, and KingdomFungi Fungi are most closely related to animals, but divergedover a billion years ago Fungi arose from protists related to Nuclearia an amoebathat feeds by engulfing cells True fungi are a monophyletic group of over 100,000species Does not include slime molds or oomycetes4Evolutionary Relationshipsof the Kingdom Fungi 5. 5Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Metazoa(animal kingdom)Choanoflagellates(protists)Nuclearia(protist)ChytridsMicrosporidiaCryptomycotaZygomycetesAM fungiAscomycetesBasidiomycetesSeptate hyphae,dikaryotic hyphae,fruiting bodiesBeneficial associations withphotosynthetic organismsCritical innovationsKEYSingle flagellumRigid chitincell wall,osmotrophicnutritionPrimarily terrestrial habitatSupergroup OpisthokontaKingdom Fungi 6. BIOLOGY PRINCIPLEAll species (past and present) are relatedby an evolutionary historyThere are more than 15 fungal phyla, buttheir relationships and names are still beingdetermined.6Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 7. Fungal cell walls Rigid cell walls are composed of chitin A tough, nitrogen-containing carbohydrate Except for the cryptomycota which lack cell walls Benefit Allows cells to resist high osmotic pressure resultingfrom feeding by absorption of small organic molecules Drawbacks Cells cannot engulf food due to rigid cell walls Restricts mobility of nonflagellated cells7 8. Seven main groups of fungi Cryptomycota Chytrids Microsporidia Zygomycetes AM fungi Ascomycetes Basidiomycetes8 9. Cryptomycota9 The earliest-diverging fungi Occur in soil and water Can produce flagella for reproduction Only fungi to lack a cell wall 10. Chytrids10 Microscopicaquatic species Have cell wallsmade of chitin Produce reproductive cells with flagella Only found in chytrids and cryptomycota Loss of flagella linked to ecological transition fromaquatic habitats to land 11. Zygomycetes11 Several lineagesof terrestrial fungi Have distinctive large zygotes called zygospores ex: Common black bread molds 12. Microsporidia12 Pathogens thatcan only reproduceinside the cells ofan animal host. Linked to honeybee decline Very small size (14 m) Single-celled, chitin-walled spores Strong chitin wall helps survival in the environmentuntil they enter the bodies of animals 13. AM fungi13 Arbuscular mycorrhizalfungi Close symbiotic associations with plant roots Fungus provides plant with minerals Plant provides food for the fungus Fossils suggest that even early plants may havedepended on these AM fungal associations 14. Ascomycetes14 Asci unique reproductive structures Some ascomycetes cause disease Ecologically important as decomposers example: Edible truffles and morels 15. Basidiomycetes Basidia club-shapedreproductive cells Very importantdecomposersand plant symbionts ~30,000 species Varied reproductive structures Mushrooms, puffballs, stinkhorns, shelves, rusts, smuts 16. 16 17. Fungi are most closely related to animals andshare several opisthokont features Both heterotrophic cannot produce their own food Both use absorptive nutrition secrete enzymesand absorb small organic molecules Both store surplus food as the carbohydrateglycogen17Fungal Bodies and Feeding 18. Unique body form Most have mycelia composed of hyphae Most of the mycelium is diffuse and inconspicuous Fruiting bodies visible reproductive structures Mushrooms are one type Fruiting bodies produce spores Spores Chitin-walled reproductive cells An adaptation to the terrestrial environment Transported by wind or by animals 18 19. 19Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Region where hyphae mate,forming a fruiting bodyMyceliumwithin substrate(such as soil)Mated hyphaeFruiting bodyabove thesubstrateSporesUnmated mycelium Different unmated mycelium 20. BIOLOGY PRINCIPLELiving organisms grow and developAfter a mating process occurs,mated hyphae produce fruiting bodieswhose form fosters spore productionand dispersal.In suitable sites, sporesmay germinate, producingnew mycelia.Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 21. Distinctive growth processes Mycelia grow quickly when food is plentiful Grow from the edges as hyphae extend their tips Narrow dimensions and extensive branchingprovides high surface area for absorption Osmosis important in growth entry of waterproduces force for tip extension21 22. 22 23. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.(a) Mycelium growing in liquidmedium Mycelium shape depends on substrate Long extensions in soil to reach food-rich areas Spherical in liquid medium Flat disk in petri dish(b) Mycelium growing on flat,solid mediuma: Agriculture and Agri-Food Canada, Southern Crop Protection and Food ResearchCentre, London ON; b: CDC 24. Many fungi reproduce by microscopic sporesthat grow into a new organism Spores may be asexual clones Or from sexual reproduction with new allelecombinations Asexual reproduction is ideal for rapid spread No need to find a mate No fruiting body No meiosis24Fungal Asexual andSexual Reproduction 25. 25 Conidia Asexual spores grownat the tips of hyphae Aspergillus versicolor Causes skin and lunginfections in vulnerablepatientsCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.69 m Dr. Dennis Kunkel Microscopy/ Visuals Unlimited 26. Medically important fungi that reproduceprimarily by asexual means include Athletes foot fungus (Epidermophyton floccosum) Infectious yeast (Candida albicans) Budding yeast, Saccharomyces cerevisiae Can reproduceeither sexuallyor by asexualbudding26Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Daughtercell (bud)Mother cell Medical-on-Line/Alamy 27. Sexual reproduction Involves union of gametes, zygote formation andmeiosis Gametes of most fungi are cells from hyphalbranches Mating types differ biochemically Hyphal branches fuse between compatiblemating types27 28. Most sexual organisms have plasmogamy(fusion of gametes cytoplasm) followed bykaryogamy (fusion of gametes nuclei) In fungi, after plasmogamy, nuclei may remainseparate for a long time Mycelium is dikaryotic or heterokaryotic Some fungi persist as dikaryons, producingclones that can live for hundreds of years Dikaryotic mycelia are functionally diploid Eventually, dikaryotic mycelia produce fruitingbodies, the next stage of reproduction28 29. Fruiting bodies Mated mycelia will produce a fleshy fruiting bodywhen conditions are right Fruiting structure disperse haploid spores that growinto mycelia If a haploid mycelium meets a compatible matingtype, they fuse (mate) and the cycle repeats Fruiting body structures aid spore dispersal Puffballs puff spores out onto wind currents Stinkhorns stink, and attract flies that carry off spores Truffles are underground but their scent attractsanimals that dig them up 29 30. 30Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.(a) Fruiting bodies adapted fordispersal of spores by windSporesin astickymatrix(b) Fruiting body adapted fordispersal of spores by insectsa: Felix Labhardt/Taxi/Getty Images; b: Bob Gibbons/ 31. Decomposer fungi are essential components ofthe Earths ecosystems Work with bacteria Only certain bacteria and fungi can break downcellulose Release minerals to the soil and water31The Importance of Fungiin Ecology and Medicine 32. Fungal pathogens Crop diseases caused by 5000 species Rust spores can be spread on the wind Human diseases Dermatophytes athletes foot, ringworm Pneumocystis jiroveci and Cryptococcus neoformans infectpeople with weakened immune systems (as in AIDS) Blastomyces dermatitidis, Coccidioides immitis, andHistoplasma capsulatum infect the lungs In nature, fungal pathogens play important ecologicalrole in controlling other species 33. 33Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.PucciniagraminissporesWheat leaf tissue0.1 mm(left): Nigel Cattlin/Photo Researchers, Inc.; (right): Herve Conge/ISM/Phototake 34. Beneficial fungal associations Fungal associations with photosyntheticpartners can be mutualistic Symbioses where both partners benefit Some animal species farm fungus for food Leaf-cutter ants, termites, beetles, salt marsh snail Mycorrhizal fungi associate with plant roots Lichens are partnerships between fungi andphotocynthetic algae or bacteria34 35. Mycorrhizae Association between the hyphae of certain fungi and theroots of most seed plants More than 80% of terrestrial plants have mycorrhizae Plants receive increased supply of water and mineralnutrients Fungi get organic food molecules from the plants Two most common types are endomycorrhizae (withinroots) and ectomycorrhizae (on roots)35 36. 36Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.SeedlingrootMycorrhizalhyphae Dr. D.P. Donelley and Prof. J.R. Leake, University of Sheffield, Department of Animal &amp; Plant Sciences 37. Endomycorrhizae Fungal hyphae penetrate the spaces between rootcell walls and plasma membranes and grow along theouter surface of the plasma membrane Arbuscular mycorrhizae (AM) form highly branchedstructures with high surface area37Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.a: Mark BrundrettHyphaeArbusculesCell wallPlasmamembrane49 m Root cells(a) Micrograph of arbuscular mycorrhizae (b) Hyphae growing between cell wallsand plasma membranes 38. Ectomycorrhizae Coat root surface and grow between cells of roots Some species of oak, beech, pine, and spruce treeswill not grow unless their ectomycorrhizal partners arealso presentRootcells38Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Ectomycorrhizalhyphae coatinga root tipEctomycorrhizalhyphae(b) SEM of ectomycorrhizal hyphae (a) Ectomycorrhizal fruiting body (c) Hyphae invading intercellular spacesa: Jacques Landry,; b: Courtesy of Larry Peterson and Hugues Massicotte 39. EVOLUTIONARY CONNECTIONSComparison of genomes reveals howbasidiomycete metabolism diversified Basidiomycete genomes show diverse metabolicpathways that help utilize organic carbon from plants Some decompose cellulose and lignin Break down dead trees, woody debris, leaf litter Some break down similar materials from animal dung Other species evolved ectomycorrhizal associationswith living plants What genes are different to give species differentcapabilities? 40. EVOLUTIONARY CONNECTIONS White rot fungi decompose both cellulose and lignin Complex enzymatic pathways to break down the many types ofchemical bonds Energetically expensive but give access to cellulose White rot fungal metabolism arose 300 mya during theCarboniferous This new set of enzymes is why there are no majorplant carbon deposits since then! Brown rot fungi break down cellulose, leave lignin Evolved from white-rot fungi but lost genes to degrade lignin,saving energy by not producing those enzymes Ectomycorrhizal fungi evolved in turn from thebrown-rot fungi 41. Lichens Partnerships of particular fungi and certain photosyntheticgreen algae and/or cyanobacteria 25,000 lichen species Not all descended from a common ancestor At least five separate fungal lineages Three major forms crustose, foliose, fruticose Photosynthetic partner provides organic food moleculesand oxygen Fungal partner provides carbon dioxide, water, andminerals41 42. 42Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.(a) Crustose lichen (b) Foliose lichen(c) Fruticose lichen (d) Microscopic view of a crosssection of a lichena: Joe McDonald/Corbis; b: Lee W. Wilcox; c: Ed Reschke/Getty Images; d: Lee W. Wilcox 43. Fungi convert inexpensive organic compounds intocitric acid, glycerol, and antibiotics Distinctive flavor of blue cheese Saccharomyces cerevisiae for bread, beer and wine Replace chemical procedures that generate harmfulwaste products Wood pulp bleaching43BiotechnologicalApplications of Fungi </p>