Fungi

1. Fungi

2. Fungi • Fleshy fungi • Yeasts • Molds • Hyphae (long filaments of joined cells) • Mycelium (intertwined mass of hyphae)

3. Fungi Are diverse and widespread Are essential for the well-being of most terrestrial ecosystems because they break down organic material and recycle vital nutrients Mushrooms

4. Nutrition and Fungal Lifestyles • Fungi are heterotrophs • But do not ingest their food • Fungi secrete into their surroundings exoenzymes that break down complex molecules • And then absorb the remaining smaller compounds

5. A General Look at Fungi - Flash Animation Note to self: may need to right chick to get to play or rewind. May need to advance slide using arrows at bottom left.

6. Fungal lifestyles • Decomposers • Parasites • Mutualistic symbionts

7. Reproductive structure.The mushroom produces tiny cells called spores. Hyphae. The mushroom and its subterranean mycelium are a network of hyphae. Spore-producing structures 20 m Mycelium Body Structure • The morphology of multicellular fungi • Enhances their ability to absorb nutrients from their surroundings

8. Structure • Fungi consist of • Mycelia, networks of branched hyphae adapted for absorption • Most fungi • Have cell walls made of chitin

9. Structure • Some fungi • Have hyphae divided into cells by septa, with pores allowing cell-to-cell movement of materials • Coenocytic fungi • Lack septa Cell wall Cell wall Nuclei Pore Septate Coenocytic Septum Nuclei (a) Septate hypha (b) Coenocytic hypha

10. Structure • Some unique fungi • Have specialized hyphae that allow them to penetrate the tissues of their host Nematode Hyphae 25 m • Hyphae adapted for • trapping and killing prey Plant cell wall Fungal hypha Plant cell Plant cell plasma membrane Haustorium (b) Haustoria – specialized hyphae that can penetrate the cell walls of plants

11. Mycorrhizae • Are mutually beneficial relationships between fungi and plant roots • Ectomycorrhizal fungi (surface) • Endomycorrhizal fungi (penetrate plant cell wall)

12. Key Heterokaryotic stage Haploid (n) Heterokaryotic (unfused nuclei from different parents) PLASMOGAMY (fusion of cytoplasm) Diploid (2n) KARYOGAMY (fusion of nuclei) Spore-producing structures Zygote SEXUAL REPRODUCTION Spores ASEXUAL REPRODUCTION Mycelium MEIOSIS GERMINATION GERMINATION Spore-producing structures Spores Reproduction/propagation Fungi produce spores through sexual or asexual life cycles (Some fungi do both, some are either sexual or asexual) • The generalized life cycle of fungi

13. Sexual Reproduction • The sexual life cycle involves • Cell fusion, plasmogamy • Nuclear fusion, karyogamy • An intervening heterokaryotic stage • Occurs between plasmogamy and karyogamy in which cells have haploid nuclei from two parents • The diploid phase following karyogamy • Is short-lived and undergoes meiosis, producing haploid spores

14. 2.5 m Asexual Reproduction • Many fungi can reproduce asexually • Many fungi that can reproduce asexually • Grow as mold, sometimes on fruit, bread, and other foods Penicillium (common saprobe on food) Conidia (asexual)

15. 10 m Parent cell Bud Asexual Reproduction • Other asexual fungi are yeasts • That inhabit moist environments • Which produce by simple cell division

16. Asexual Reproduction • Many molds and yeasts have no known sexual stage • Mycologists have traditionally called these deuteromycetes, or imperfect fungi

17. Evolution/Origin of Fungi • Fungi descended from an aquatic, single-celled, flagellated protist • Systematists now recognize Fungi and Animalia as sister kingdoms • Because fungi and animals are more closely related to each other than they are to plants or other eukaryotes • Molecular evidence • Supports the hypothesis that fungi and animals diverged from a common ancestor that was unicellular and bore flagella • Fungi probably evolved • Before the colonization of land by multicellular organisms

18. 50 m Origin of Fungi • The oldest undisputed fossils of fungi are only about 460 million years old • Fungi were among the earliest colonizers of land. • -Probably as symbionts with early land plants Fossil hyphae and spores

19. Arbuscular mycorrhizal fungi Zygote fungi Club fungi Sac fungi Chytrids Zygomycota Ascomycota Basidiomycota Glomeromycota Chytridiomycota Phylogeny/Classification • Fungi have radiated into a diverse set of lineages • The phylogeny of fungi • Is currently the subject of much research • Molecular analysis has helped clarify the evolutionary relationships between fungal groups, although there are still areas of uncertainty

20. Phylogeny/Classification Five Phyla of Fungi

21. Chytrids • Fungi classified in the phylum Chytridiomycota, or chytrids • Are found in freshwater and terrestrial habitats • Can be saprobic or parasitic

22. 25 m Hyphae Flagellum 4 m Chytrids • Chytrids are unique among fungi • In having flagellated spores, called zoospores

23. Chytrids • Until recently, systematists thought that • Fungi lost flagella only once in their history • Molecular data • Indicate that some “chytrids” are closely related to another fungal group, the zygomycetes Glomeromycetes, ascomycetes, andbasidiomycetes Zygomycetes and other chytrids Some chytrids Key Common ancestor Loss of flagella

24. Zygomycetes • Fungi in the phylum Zygomycota, the zygomycetes • Exhibit a considerable diversity of life histories • Include fast-growing molds, parasites, and commensal symbionts • Are named for their sexually produced zygosporangia

25. Neighboring mycelia of different mating types form hyphal extensions called gametangia, each walled off around several haploid nuclei by a septum. Mycelia have various mating types (here designated +, with red nuclei, and, with blue nuclei). 1 2 Key Haploid (n) Heterokaryotic (n + n) Diploid A heterokaryoticzygosporangiumforms, containingmultiple haploidnuclei from the twoparents. 3 PLASMOGAMY Rhizopusgrowing on bread Mating type (+) Gametangia with haploid nuclei Mating type () 100 m The spores germinate and grow into new mycelia. 8 Young zygosporangium (heterokaryotic) Mycelia can also reproduce asexually by forming sporangia that produce genetically identical haploid spores. 9 SEXUAL REPRODUCTION Dispersal and germination Sporangia 7 The sporangium disperses genetically diverse, haploid spores. Zygosporangium (heterokaryotic) KARYOGAMY Diploid nuclei This cell develops a rough, thick-walled coating that can resist dry environments and other harsh conditions for months. 4 Sporangium ASEXUAL REPRODUCTION MEIOSIS Dispersal and germination 50 m Mycelium When conditions are favourable, karyogamy occurs, followed by meiosis. 5 The zygosporangium then breaks dormancy, germinating into a short sporangium. 6 Zygomycetes - Life Cycle • The life cycle of Rhizopus stolonifer(fairly typical of zygomycetes)

26. 0.5 mm Zygomycetes • Some zygomycetes, such as Pilobolus • Can actually “aim” their sporangia toward conditions associated with good food sources This decomposer of animal dung bends toward bright light and shoots its sporangia up to 2 meters

27. Spore dispersal movie

28. Zygomycetes • Zygosporangia, which are resistant to freezing and drying • Are capable of persisting through unfavorable conditions • Can undergo meiosis when conditions improve

29. 10 m Host cell nucleus Developing microsporidian Spore Microsporidia • Microsporidia • Are unicellular parasites of animals and protists • A taxonomic mystery…Are now classified as zygomycetes (But that could change at any time!) This cell is infected with the parasitic fungus Encephalitozoon intestinalis

30. Glomeromycetes • Fungi assigned to the phylum Glomeromycota • Were once considered zygomycetes • Are now classified in a separate clade

31. 2.5 m Glomeromycetes • All glomeromycetes • Form a distinct type of endomycorrhizae called arbuscular mycorrhizae Picture shows cytoplasm removed to show the arbuscule (branched structure) inside plant cell.

32. Ascomycetes • Fungi in the phylum Ascomycota • Are found in a variety of marine, freshwater, and terrestrial habitats • Are defined by the production of sexual spores in saclike asci, which are usually contained in fruiting bodies called ascocarps • Have asexual reproduction by producing enormous numbers of asexual spores called conidia

33. (a)The cup-shaped ascocarps (fruiting bodies) of Aleuria aurantia give this species its common name: orange peel fungus. (b) The edible ascocarp of Morchella esculenta, the succulent morel, is often found under trees in orchards. 10 m (c)Tuber melanosporum is a truffle, an ascocarp that grows underground and emits strong odors. These ascocarps have been dug up and the middle one sliced open. (d)Neurospora crassa feeds asa mold on bread and other food (SEM). Ascomycetes • Ascomycetes • Vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels

34. Neurospora can reproduce sexually by producing specialized hyphae. Conidia of the opposite mating type fuse to these hyphae. Ascomycete mycelia can also reproduce asexually by producing haploid conidia. Key Conidia;mating type () 1 7 Haploid (n) Dikaryotic (n n) Diploid (2n) Dispersal Germination Matingtype () ASEXUALREPRODUCTION Mycelium PLASMOGAMY A dikaryotic ascus develops. 2 Ascogonium Ascus(dikaryotic) Mycelia Conidiophore Dikaryotichyphae Karyogamy occurs within theascus, producing adiploid nucleus. SEXUALREPRODUCTION KARYOGAMY Germination The developing asci are contained in an ascocarp. The ascospores are discharged forciblyfrom the asci through anopening in the ascocarp. Germinating ascosporesgive rise to new mycelia. Dispersal 3 Diploid nucleus(zygote) Eightascospores Asci 6 Fourhaploidnuclei MEIOSIS Ascocarp Each haploid nucleus dividesonce by mitosis, yielding eightnuclei. Cell walls develop aroundthe nuclei, forming ascospores (LM). 4 The diploid nucleusdivides by meiosis, yieldingfour haploid nuclei. 5 Ascomycetes – Life Cycle • The life cycle of Neurospora crassa

35. Basidiomycetes • Fungi in the phylum Basidiomycota • Include mushrooms and shelf fungi • Are defined by a clublike structure called a basidium, a transient diploid stage in the life cycle

36. (b) Maiden veil fungus (Dictyphora), a fungus with an odor like rotting meat (a) Fly agaric (Amanita muscaria), acommon species in conifer forests in the northern hemisphere (d) Puffballs emitting spores (c) Shelf fungi, important decomposers of wood Basidiomycetes

37. Basidiomycetes • The life cycle of a basidiomycete • Usually includes a long-lived dikaryotic mycelium, which can erect its fruiting structure, a mushroom, in just a few hours Fairy rings can appear overnight. A very large mycelium is growing underneath this ring of fruiting structures

38. A dikaryotic mycelium forms, growing faster then, and ultimately crowding out, the haploid parental mycelia. 2 1 Two haploid mycelia of different mating typesundergo plasmogamy. Environmental cues such as rain ortemperature changes induce the dikaryoticmycelium to formcompact masses thatdevelop intobasidiocarps(mushrooms, in thiscase). Dikaryoticmycelium 3 PLASMOGAMY In a suitableenvironment, thebasidiospores germinate andgrow intoshort-livedhaploid mycelia. Matingtype () 8 Matingtype () Haploidmycelia Gills linedwith basidia SEXUALREPRODUCTION Basidiocarp(dikaryotic) Dispersalandgermination When mature,the basidiosporesare ejected, fallfrom the cap, andare dispersed bythe wind. 7 Basidiospores Basidia(dikaryotic) Basidium withfour appendages Basidium containingfour haploid nuclei Basidium The basidiocarpgills are lined withterminal dikaryoticcells called basidia. 4 KARYOGAMY MEIOSIS Each diploid nucleus yields four haploid nuclei. Each basidiumgrows four appendages, and one haploid nucleusenters each appendage and develops into a basidiospore (SEM). 6 Key Diploidnuclei Haploid (n) Karyogamy in the basidia produces diploidnuclei, which thenundergo meiosis. 5 Dikaryotic (n n) 1 m Basidiospore Diploid (2n) Basidiomycetes • The life cycle of a mushroom-forming basidiomycete

39. Fungi have a powerful impact on ecosystems and human welfare

40. Decomposers • Fungi are well adapted as decomposers of organic material • Performing essential recycling of chemical elements between the living and nonliving world

41. Symbionts • Fungi form symbiotic relationships with • Plants, algae, and animals

42. EXPERIMENT Researchers grew soybean plants in soil treated with fungicide (poison that kills fungi) to prevent the formation of mycorrhizae in the experimental group. A control group was exposed to fungi that formed mycorrhizae in the soybean plants’ roots. The soybean plant on the left is typical of the experimental group. Its stunted growth is probably due to a phosphorus deficiency. The taller, healthier plant on the right is typical of the control group and has mycorrhizae. CONCLUSION These results indicate that the presence of mycorrhizae benefits a soybean plant and support the hypothesis that mycorrhizae enhance the plant’s ability to take up phosphate and other needed minerals. Mycorrhizae • Mycorrhizae • Are enormously important in natural ecosystems and agriculture • Increase plant productivity RESULTS RESULTS

43. Fungus-Animal Symbiosis • Some fungi share their digestive services with animals • Helping break down plant material in the guts of cows and other grazing mammals

44. Many species of ants and termites • Take advantage of the digestive power of fungi by raising them in “farms”

45. Leaf cutter ant movie

46. (a) A fruticose (shrub-like) lichen (b) A foliose (leaf-like) lichen (c) Crustose (crust-like) lichens Lichens • Lichens • Are a symbiotic association of millions of photosynthetic microorganisms held in a mass of fungal hyphae

47. Ascocarp of fungus Soredia Fungal hyphae Algal layer Algal cell Fungal hyphae 10 m Lichen • The fungal component of a lichen • Is most often an ascomycete • Algae or cyanobacteria • Occupy an inner layer below the lichen surface

48. (b) Tar spot fungus on maple leaves (a) Corn smut on corn (c) Ergots on rye Pathogens • About 30% of known fungal species • Are parasites, mostly on or in plants. • Some of the fungi that attack food crops • Are toxic to humans

49. Staphylococcus Penicillium Zone of inhibited growth Practical Uses of Fungi • Humans eat many fungi • And use others to make cheeses, alcoholic beverages, and bread • Genetic research on fungi • Is leading to applications in biotechnology • Antibiotics produced by fungi-treat bacterial infections

50. Fungi: Wrap-up video clip