1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 31 Fungi

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fungi Are diverse and widespread Master recyclers of nutrients in terrestrial environments. Land Plants – supply plants with key nutrients Speed the Carbon Cycle on Land – decompose dead wood Important Economic Impacts Figure 31.1

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mycorrhizae – Are mutually beneficial relationships between fungi and plant roots

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fungi Feed Land Plants Mycorrhizae – Are mutually beneficial relationships between fungi and plant roots Mycorrhizal Associations allow faster plant growth

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fungi Speed the Carbon Cycle on Land Saprophytes are fungi that make their living by digesting dead plant material. Dip in the fossil record of saprophytic fungi during the Carboniferous – hypothesized that their absence was responsible for the enormous buildup of dead plant material in that period Spike in the number of fungal fossils at the end of the Permian – coinciding with the greatest mass extinction in history – indicated that land plants as well as marine organisms were devastated

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7. Role of Fungi in Carbon Cycle

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Important Economic Impacts Incidence of fungal infections in humans is very low – parasitic fungi cause athlete’s foot vaginitis diaper rash ringworm pneumonia thrush major destructive impact is on crops

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Destructive Impact on Crops

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Distribution of Fungi About 80,000 species of fungi described and named About 1000 more discovered each year known species widely regarded as a tiny fraction of the real total

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings To predict the actual number of species alive today, one researcher looked at the ratio of vascular plant species to fungal species in the British Isles. His analysis showed an average of six species of fungus for every species of vascular plant. If this ratio holds worldwide, the total of 275,000 vascular plant species implies that there are 1.65 million species of fungi.

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Analyzing Morphological Traits Fungi have very simple bodies. Cell walls made of chitin Two growth forms exist: – yeasts single-celled – mycelia multicellular filamentous forms Some fungi adopt both life-forms.

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15. hyphae – Filaments that make up a mycelium – most haploid (heterokaryotic) – May be divided into cell-like compartments by septa Fungal Mycelium

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some fungi – Have hyphae divided into cells by septa, with pores allowing cell-to-cell movement of materials Coenocytic fungi – Lack septa Nuclei Cell wall Septum Pore (a) Septate hypha(b) Coenocytic hypha Cell wall Nuclei Figure 31.3a, b

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18. Nutrition Fungi are heterotrophs Digestion takes place outside their cells – exoenzymes break down complex molecules – absorb the smaller compounds – morphology provides a large amount of surface area for efficient absorption

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Body Structure Enhances Nutrition The morphology of multicellular fungi – Enhances their ability to absorb nutrients from their surroundings Hyphae. The mushroom and its subterranean mycelium are a continuous network of hyphae. Reproductive structure. The mushroom produces tiny cells called spores. Spore-producing structures 20  m Mycelium Figure 31.2

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some unique fungi – Have specialized hyphae that allow them to penetrate the tissues of their host Nematode Hyphae 25  m (a) Hyphae adapted for trapping and killing prey (b) Haustoria Fungal hypha Plant cell wall Haustorium Plant cell plasma membrane Plant cell Figure 31.4a, b

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Life Cycles Fungi produce spores through sexual or asexual life cycles Fungi propagate themselves – By producing vast numbers of spores, either sexually or asexually

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The generalized life cycle of fungi Key Haploid (n) Heterokaryotic (unfused nuclei from different parents) Diploid (2n) PLASMOGAMY (fusion of cytoplasm) Heterokaryotic stage KARYOGAMY (fusion of nuclei) SEXUAL REPRODUCTION Spore-producing structures Spores ASEXUAL REPRODUCTION Zygote Mycelium GERMINATION MEIOSIS Spore-producing structures Spores Figure 31.5

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The diploid phase following karyogamy – Is short-lived and undergoes meiosis, producing haploid spores

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Major Groups Based on Reproductive Structures

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 1.Chytridiomycota (chytrids) live primarily in water and have spores and gametes with flagella (Figure 30.7a).

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28. 2.Zygomycota have haploid hyphae of different mating types. If two hyphae are of different mating types, the individuals may become yoked together. Cells from the yoked hyphae fuse to form a spore-producing structure called a zygosporangium

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30. 3.Basidiomycota, or club fungi, have basidia that form at the ends of hyphae and produce spores Mushrooms, bracket fungi, and puffballs are among the complex reproductive structures this group produces.

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32. 4.Ascomycota, or sac fungi, produce complex reproductive structures—the largest of which are often cup-shaped. The tips of hyphae inside these structures produce distinctive saclike cells, called asci, that generate spores

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34. Asexual Many fungi that can reproduce asexually – Grow as mold, sometimes on fruit, bread, and other foods 2.5  m Figure 31.6

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Other asexual fungi are yeasts – That inhabit moist environments – Which produce by simple cell division 10  m Parent cell Bud Figure 31.7

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many molds and yeasts have no known sexual stage – Mycologists have traditionally called these Deuteromycetes or Fungi Imperfecti imperfect fungi

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 31.3: 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

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Origin of Fungi 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

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The oldest undisputed fossils of fungi – Are only about 460 million years old 50  m Figure 31.8

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41. Based on the assumption that fungi evolved from aquatic protists, researchers hypothesized that chytrids were the most basal group and that ascomycetes and basidiomycetes—with their more complex reproductive structures— were the most recent to evolve.

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Relationships among Major Fungal Groups Ribosomal RNA sequencing supports the hypothesis that the ascomycetes and basidiomycetes are monophyletic chytrids and zygomycetes are not The data also support the conclusion that the chytrids are the most basal group of fungi.

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45. First, based on the close relationship between fungi and unusual, single-celled parasites called microsporidians, researchers are testing the hypothesis that fungicides— molecules that are lethal to fungi—may prove effective in combating microsporidian infections in humans with AIDS.

46. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Second, fungi are more closely related to animals than to land plants. For example, most animals and fungi synthesize the tough structural material called chitin. Also, the flagella that develop in chytrid spores and in chytrid gametes are very similar to those observed in animals.

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A review of fungal phyla Table 31.1

48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chytrids Fungi classified in the phylum Chytridiomycota, or chytrids – Are found in freshwater and terrestrial habitats – Can be saprobic or parasitic

49. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chytrids are unique among fungi – In having flagellated spores, called zoospores 25  m 4  m Hyphae Flagellum Figure 31.10

50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Until recently, systematists thought that – Fungi lost flagella only once in their history Molecular data – Indicate that some “chytrids” are actually more closely related to another fungal group, the zygomycetes Some chytrids Zygomycetes and other chytrids Glomeromycetes, ascomycetes, and basidiomycetes Common ancestor Key Loss of flagella Figure 31.11

51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Rhizopus growing on bread ASEXUAL REPRODUCTION Mycelium Dispersal and germination MEIOSIS KARYOGAMY PLASMOGAMY Key Haploid (n) Heterokaryotic (n + n) Diploid Sporangium Diploid nuclei Zygosporangium (heterokaryotic) 100  m Young zygosporangium (heterokaryotic) SEXUAL REPRODUCTION Dispersal and germination Mating type (+) Mating type (  ) Gametangia with haploid nuclei 50  m Sporangia The life cycle of Rhizopus stolonifer – Is fairly typical of zygomycetes Mycelia have various mating types (here designated +, with red nuclei, and , with blue nuclei). 1 Neighboring mycelia of different mating types form hyphal extensions called gametangia, each walled off around several haploid nuclei by a septum. 2 A heterokaryotic zygosporangium forms, containing multiple haploid nuclei from the two parents. 3 The sporangium disperses genetically diverse, haploid spores. 7 4 This cell develops a rough, thick-walled coating that can resist dry environments and other harsh conditions for months. 5 When conditions are favourable, karyogamy occurs, followed by meiosis. 6 The zygosporangium then breaks dormancy, germinating into a short sporangium. The spores germinate and grow into new mycelia. 8 9 Mycelia can also reproduce asexually by forming sporangia that produce genetically identical haploid spores. Figure 31.12

53. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some zygomycetes, such as Pilobolus – Can actually “aim” their sporangia toward conditions associated with good food sources 0.5 mm Figure 31.13

54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Zygosporangia, which are resistant to freezing and drying – Are capable of persisting through unfavorable conditions – Can undergo meiosis when conditions improve

55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Microsporidia – Are unicellular parasites of animals and protists – Are now classified as zygomycetes 10  m Host cell nucleus Developing microsporidian Spore Figure 31.14

56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Glomeromycetes Fungi assigned to the phylum Glomeromycota – Were once considered zygomycetes – Are now classified in a separate clade

57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings All glomeromycetes – Form a distinct type of endomycorrhizae called arbuscular mycorrhizae 2.5  m Figure 31.15

58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

59. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ascomycetes – Vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels (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. (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 as a mold on bread and other food (SEM). 10  m Figure 31.16a–d

60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ascomycetes reproduce – Asexually by producing enormous numbers of asexual spores called conidia

61. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The life cycle of Neurospora crassa, an ascomycete Dispersal ASEXUAL REPRODUCTION Germination Mycelium Conidiophore Germination Dispersal Mycelia Asci Eight ascospores Ascocarp Four haploid nuclei MEIOSIS KARYOGAMY PLASMOGAMY SEXUAL REPRODUCTION Diploid nucleus (zygote) Ascogonium Ascus (dikaryotic) Dikaryotic hyphae Mating type (  ) Conidia; mating type (  ) Key Haploid (n) Dikaryotic (n  n) Diploid (2n) Ascomycete mycelia can also reproduce asexually by producing haploid conidia. 7 Neurospora can reproduce sexually by producing specialized hyphae. Conidia of the opposite mating type fuse to these hyphae. 1 A dikaryotic ascus develops. 2 Karyogamy occurs within the ascus, producing a diploid nucleus. 3 The diploid nucleus divides by meiosis, yielding four haploid nuclei. 4 The developing asci are contained in an ascocarp. The ascospores are discharged forcibly from the asci through an opening in the ascocarp. Germinating ascospores give rise to new mycelia. 6 5 Each haploid nucleus divides once by mitosis, yielding eight nuclei. Cell walls develop around the nuclei, forming ascospores (LM). Figure 31.17

62. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

63. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Basidiomycetes (a) Fly agaric (Amanita muscaria), a common species in conifer forests in the northern hemisphere (b) Maiden veil fungus (Dictyphora), a fungus with an odor like rotting meat (c) Shelf fungi, important decomposers of wood (d) Puffballs emitting spores Figure 31.18a–d

64. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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 Figure 31.19

65. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PLASMOGAMY Dikaryotic mycelium Basidiocarp (dikaryotic) KARYOGAMY Key MEIOSIS Gills lined with basidia SEXUAL REPRODUCTION Mating type (  ) Mating type (  ) Haploid mycelia Dispersal and germination Basidiospores Basidium with four appendages Basidium containing four haploid nuclei Basidia (dikaryotic) Diploid nuclei Basidiospore 1  m Basidium Haploid (n) Dikaryotic (n  n) Diploid (2n) The life cycle of a mushroom-forming basidiomycete Each diploid nucleus yields four haploid nuclei. Each basidium grows four appendages, and one haploid nucleus enters each appendage and develops into a basidiospore (SEM). 6 Two haploid mycelia of different mating types undergo plasmogamy. 1 A dikaryotic mycelium forms, growing faster then, and ultimately crowding out, the haploid parental mycelia. 2 3 Environmental cues such as rain or temperature changes induce the dikaryotic mycelium to form compact masses that develop into basidiocarps (mushrooms, in this case). The basidiocarp gills are lined with terminal dikaryotic cells called basidia. 4 Karyogamy in the basidia produces diploid nuclei, which then undergo meiosis. 5 When mature, the basidiospores are ejected, fall from the cap, and are dispersed by the wind. 7 In a suitable environment, the basidiospores germinate and grow into short-lived haploid mycelia. 8 Figure 31.20

66. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 31.5: Fungi have a powerful impact on ecosystems and human welfare

67. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Decomposers Fungi are well adapted as decomposers of organic material – Performing essential recycling of chemical elements between the living and nonliving world

68. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symbionts Fungi form symbiotic relationships with – Plants, algae, and animals

69. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

70. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many species of ants and termites – Take advantage of the digestive power of fungi by raising them in “farms” Figure 31.22

71. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lichens – Are a symbiotic association of millions of photosynthetic microorganisms held in a mass of fungal hyphae (a) A fruticose (shrub-like) lichen (b) A foliose (leaf-like) lichen (c) Crustose (crust-like) lichens Figure 31.23a–c

72. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The fungal component of a lichen – Is most often an ascomycete Algae or cyanobacteria – Occupy an inner layer below the lichen surface Ascocarp of fungus Fungal hyphae Algal layer Soredia Algal cell Fungal hyphae 10  m Figure 31.24

73. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pathogens About 30% of known fungal species – Are parasites, mostly on or in plants (a) Corn smut on corn (b) Tar spot fungus on maple leaves (c) Ergots on rye Figure 31.25a–c

74. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some of the fungi that attack food crops – Are toxic to humans

75. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Practical Uses of Fungi Humans eat many fungi – And use others to make cheeses, alcoholic beverages, and bread

76. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Antibiotics produced by fungi – Treat bacterial infections Staphylococcus Penicillium Zone of inhibited growth Figure 31.26

77. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Genetic research on fungi – Is leading to applications in biotechnology