1. Kingdom Fungi
Chapter 26

2. Learning Objective 1
What are the distinguishing characteristics of kingdom Fungi?

3. Fungi Eukaryotic heterotrophs Secrete digestive enzymes onto food
then absorb predigested food
Cell walls with chitin

4. KEY CONCEPTS
Fungi are eukaryotic heterotrophs that absorb nutrients from their surroundings

5. Learning Objective 2
What is the body plan of a fungus?

6. Fungi Structures Fungi include Most multicellular fungi
unicellular yeast
filamentous, multicellular mold
Most multicellular fungi
have long, threadlike filaments (hyphae)
branch and form a tangled mass (mycelium)

7. Insert “Mycelium”
mycelium.swf

8. Learn more about mycelium by clicking on the figure in ThomsonNOW.

9. Hyphae In most fungi In some fungi
perforated septa (cross walls) divide hyphae into individual cells
In some fungi
zygomycetes and glomeromycetes
hyphae are coenocytic (form elongated, multinuclear cell)

10. Fungus Body Plan

11. Hyphae
Figure 26.1: Fungus body plan.
25 µm
Fig (a-b), p. 557

12. Figure 26.1: Fungus body plan.
Fig (c-e), p. 557

13. KEY CONCEPTS
A fungus may be a unicellular yeast or a filamentous, multicellular mold consisting of long, branched hyphae that form a mycelium

14. Learning Objective 3
What is the life cycle of a typical fungus, including sexual and asexual reproduction?

15. Reproduction Most fungi reproduce sexually and asexually by spores
produced on aerial hyphae
land in suitable spot and germinate

16. Germination of a Spore

17. Spore Hypha Mycelium Fig. 26-2, p. 557
Figure 26.2: Germination of a spore to form a mycelium.
Mycelium
Fig. 26-2, p. 557

18. Asexual Reproduction

19. Bud development Fig. 26-3a, p. 558
Figure 26.3: Yeasts are unicellular fungi.
Bud development
Fig. 26-3a, p. 558

20. Figure 26.3: Yeasts are unicellular fungi.
Fig. 26-3b, p. 558

21. Plasmogamy Fungi of two different mating types meet, hyphae fuse
cytoplasm fuses
nuclei remain separate
Fungi enter dikaryotic (n + n) stage
each new cell has one nucleus of each type

22. Karyogamy Fusion of nuclei takes place in hyphal tip
results in diploid (2n) zygote nucleus

23. Genetic Divisions Meiosis Mitosis
produces 4 different haploid (n) nuclei
each nucleus becomes part of a spore
Mitosis
forms new mycelia when spores germinate

24. Asexual Spores Can be produced by mitosis When these spores germinate
genetically similar
When these spores germinate
they also develop into mycelia

25. Fungal Life Cycles

26. Dikaryotic stage (n + n)7 8
Spore germinates and forms mycelium by mitosis.
Large numbers of haploid (n) spores are produced by mitosis.
Asexual reproduction
Mycelia of two different mating types fuse at their tips, and plasmogamy (fusion of cytoplasm) occurs.
Spores germinate and form mycelia by mitosis. 1 2
Mycelia 6
Sexual reproduction
Spores are released.
Spores
Haploid stage (n)
Plasmogamy
Dikaryotic stage (n + n) 5
Diploid stage (2n)
Meiosis results in four genetically different haploid ( n ) nuclei. Spores develop around nuclei.
Figure 26.4: The basic sequence of events in most fungal life cycles. 3
Dikaryotic (n + n) mycelium develops.
Zygote nucleus (2n)
Dikaryotic mycelium
Meiosis
Karyogamy
Karyogamy (fusion of nuclei) occurs, forming a diploid (2 n ) zygote nucleus. 4
Fig. 26-4, p. 559

27. KEY CONCEPTS
Most fungi reproduce both asexually and sexually by means of spores

28. Learning Objective 4
Support the hypothesis that fungi are opisthokonts, more closely related to animals than to plants

29. Flagellate Cells Animals and fungi have flagellate cells
Example: chytrid gametes and spores
Flagellate cells propel themselves
with single posterior flagellum

30. Platelike Cristae
Like animal cells, fungal cells have platelike cristae in their mitochondria

31. Opisthokonts Fungi are opisthokonts
along with animals and choanoflagellates
based on chemical and structural characters

32. Fungal Evolution

33. Evolution of ascospores
Glomeromycetes
Basidiomycetes
Zygomycetes
Ascomycetes
Chytrids
Evolution of ascospores
Evolution of basidiospores
Evolution of dikaryotic stage
Figure 26.5: Fungal evolution: cladogram of major phyla of fungi.
This cladogram shows phylogenetic relationships among living fungi, based on comparisons of ribosomal and nuclear gene sequence data for many species. The chytrids were the lineage that branched off first during fungal evolution. Note that ascomycetes and basidiomycetes are sister clades. Remember that the phylogeny of fungi is a work in process.
Loss of flagellum
Common flagellate ancestor
Fig. 26-5, p. 560

34. Learning Objective 5
Support the hypothesis that chytrids may have been the earliest fungal group to evolve from the most recent common ancestor of fungi

35. Chytrids (Chytridiomycetes)
Produce flagellate cells during life cycle
no other fungi have flagella
Probably earliest fungi to evolve from flagellate protist
common ancestor of all fungi

36. Chytrid

37. 5 µm Fig. 26-6, p. 561 Figure 26.6: Chytrid.
Nomarski differential interference micrograph of a common chytrid (Chytridium convervae). Many chytrids have a microscopic body form consisting of a rounded, coenocytic thallus and branched rhizoids that superficially resemble roots. The rhizoids may anchor the chytrid thallus and absorb predigested food.
5 µm
Fig. 26-6, p. 561

38. Learning Objective 6
List distinguishing characteristics, describe a typical life cycle, and give examples of each of these fungal groups:
chytridiomycetes
zygomycetes
glomeromycetes
ascomycetes
basidiomycetes

39. Chytrids 1 Reproduce both asexually and sexually
Gametes and zoospores are flagellate
Allomyces
part of life is multicellular haploid thallus
part is multicellular diploid thallus

40. Chytrids 2
Haploid thallus produces 2 types of flagellate gametes that fuse
Both plasmogamy and karyogamy occur
producing flagellate zygote

41. Chytrids 3 Diploid thallus bears zoosporangia
produce diploid zoospores, resting sporangia
in which haploid zoospores form by meiosis
Haploid zoospores form new haploid thalli

42. Chytrid Life Cycle

43. Common flagellate ancestor
Glomeromycetes
Basidiomycetes
Zygomycetes
Ascomycetes
Chytrids
Figure 26.7: Life cycle of Allomyces arbuscula, a chytrid.
Allomyces alternates between haploid and diploid stages, which are similar in appearance.
Common flagellate ancestor
Fig. 26-7a, p. 562

44. HAPLOID (n) GENERATION DIPLOID (2n) GENERATION
Mature haploid thallus
Haploid thallus produces two types of gametes by mitosis.
Sporangium 2 1
Haploid zoospore
Gamete type A
Haploid zoospore grows into haploid thallus.
Gamete type B 6
Haploid zoospores are produced by meiosis.
SEXUAL REPRODUCTION
HAPLOID (n) GENERATION
Gametes fuse and their nuclei fuse, producing flagellate zygote.
Resting sporangium 3
DIPLOID (2n) GENERATION
Plasmogamy and karyogamy
Meiosis 5
Resting sporangium
Motile zygote
Meiosis occurs in resting sporangia.
Figure 26.7: Life cycle of Allomyces arbuscula, a chytrid.
Allomyces alternates between haploid and diploid stages, which are similar in appearance.
Zoosporangium 4
Zygote germinates and develops into diploid thallus.
Zoosporangia produce flagellate diploid zoospores by mitosis. Zoospores give rise to new diploid thalli.
ASEXUAL REPRODUCTION (by mitosis) 7
Diploid zoospore
Fig. 26-7b, p. 562

45. Zygomycetes 1 Rhizopus (black bread mold) Asexual spores germinate
forms haploid thallus
produces asexual spores and sexual spores
Asexual spores germinate
form new thalli

46. Zygomycetes 2 In sexual reproduction Plasmogamy occurs
hyphae of 2 different haploid mating types form gametangia
Plasmogamy occurs
as gametangia fuse

47. Zygomycetes 3 Karyogamy occurs Meiosis diploid zygote forms
from which zygospore develops
Meiosis
produces recombinant haploid zygospores

48. Zygomycetes 4 When zygospores germinate Spores are released
each hypha develops a sporangium at its tip
Spores are released
develop into new hyphae

49. Zygomycete Life Cycle

50. Common flagellate ancestor
Glomeromycetes
Basidiomycetes
Zygomycetes
Ascomycetes
Chytrids
Figure 26.9: Life cycle of the black bread mold (Rhizopus stolonifer), a zygomycete.
Common flagellate ancestor
Fig. 26-9a, p. 564

51. Figure 26.9: Life cycle of the black bread mold (Rhizopus stolonifer), a zygomycete.
Fig. 26-9b, p. 564

52. Insert “Zygomycete life cycle”
rhizopus_life_cycle.swf

53. Microsporidia Microsporidia (now zygomycetes)
are opportunistic pathogens
penetrate and infect animal cells with long, threadlike polar tubes

54. Infection by Microsporidium

55. Spore of microsporidium has coiled
Microsporidian cell
Polar tube
Host cell
Figure 26.10: Infection by microsporidium. 1
Spore of microsporidium has coiled
polar tube. 2
Spore ejects
its polar tube and penetrates host cell. 3
Infective cytoplasm is injected into host cell.
Fig , p. 565

56. 1. Spore of microsporidium has coiled
Microsporidian cell
Polar tube
1. Spore of microsporidium has coiled
polar tube.
2. Spore ejects
its polar tube and penetrates host cell.
3. Infective cytoplasm is injected into host cell.
Host cell
Figure 26.10: Infection by microsporidium.
Stepped Art
Fig , p. 565

57. Glomeromycetes 1 Phylum Glomeromycota Endomycorrhizal fungi
symbionts that form intracellular associations (mycorrhizae) with plant roots
Endomycorrhizal fungi
extend hyphae into root cells

58. Glomeromycetes 2 Arbuscular mycorrhizae Glomeromycetes
most common endomycorrhizae
hyphae inside root cells form branched, tree-shaped structures (arbuscules)
Glomeromycetes
have coenocytic hyphae
reproduce asexually with large, multinucleate spores (blastospores)

59. Arbuscular Mycorrhizae

60. Cells of root cortex Root epidermis Soil Vesicle Root hair Arbuscule
Spore
Figure 26.11: Arbuscular mycorrhizae.
This mycelium has grown into the root. Its hyphae branch between the cells of the root. Hyphae have penetrated through the cell walls of two root cells and have branched extensively to form arbuscules. The tip of one hypha between root cells has enlarged and serves as a vesicle that stores food. The tip of a hypha in the soil has enlarged, forming a spore. The spaces between the root cells have been magnified.
Cortex cell
Hyphae of fungus
Fig , p. 565

61. Ascomycetes 1 Produce asexual spores (conidia)
Produce sexual spores (ascospores) in asci
Asci line a fruiting body (ascocarp)

62. Conidia
Ascocarp
Asci

63. Ascomycetes 2
Haploid mycelia of opposite mating types produce septate hyphae
Plasmogamy occurs, nuclei exchanged
Dikaryotic n + n stage occurs
hyphae form, produce asci and ascocarp

64. Ascomycetes 3 Karyogamy occurs Recombinant nuclei divide by mitosis
followed by meiosis
Recombinant nuclei divide by mitosis
produce 8 haploid nuclei that develop into ascospores
When ascospores germinate
can form new mycelia

65. Ascomycetes 4 Ascomycetes include Some ascomycetes form mycorrhizae
yeasts
cup fungi
morels
truffles
pink, brown, and blue-green molds
Some ascomycetes form mycorrhizae
others form lichens

66. Ascomycete Life Cycle

67. Common flagellate ancestor
Glomeromycetes
Basidiomycetes
Zygomycetes
Ascomycetes
Chytrids
Figure 26.13: Life cycle of a typical ascomycete.
Sexual reproduction requires haploid mycelia of different mating types. Note the dikaryotic stage and the separation of plasmogamy and karyogamy. Steps ●5 – ●8 take place within an ascus in the ascocarp.
Common flagellate ancestor
Fig a, p. 567

68. ASEXUAL REPRODUCTION (by conidia)10
Germinating conidium
In asexual reproduction, hyphae produce haploid conidia that can develop into new mycelia.
ASEXUAL REPRODUCTION (by conidia)
Haploid (n)
Conidiophore
When released, ascospores germinate and form new haploid mycelia. 9
(+) mating type
Haploid mycelia of opposite mating types both produce coenocytic sexual hyphae. 1
(–) mating type 2
Plasmogamy 8
Plasmogamy occurs as hyphae of the two mating types fuse and nuclei are exchanged.
Nuclei migrate
Each nucleus becomes incorporated into an ascospore.
SEXUAL REPRODUCTION 3
HAPLOID ( n ) STAGE
Dikaryotic hyphae form and produce asci.
Mitosis produces eight haploid nuclei.
DIKARYOTIC STAGE
(n + n) 7
Mature ascus has eight haploid ascospores
Hyphae form an ascocarp.
First meiotic division 4
DIPLOID (2n) STAGE
Figure 26.13: Life cycle of a typical ascomycete.
Sexual reproduction requires haploid mycelia of different mating types. Note the dikaryotic stage and the separation of plasmogamy and karyogamy. Steps ●5 – ●8 take place within an ascus in the ascocarp.
Developing ascus
with
n + n
nuclei
Second meiotic division
Nuclei fuse
Zygote
Meiosis
Ascocarp 6
Meiosis occurs, forming four haploid nuclei.
Karyogamy 5
Mycelium
Karyogamy occurs in each ascus. Two haploid nuclei fuse, forming a diploid zygote nucleus.
Fig b, p. 567

69. Insert “Sac fungi”
sac_fungi_m.swf

70. Basidiomycetes 1 Produce sexual spores (basidiospores) Basidia develop
on outside of basidium
Basidia develop
on surface of gills in mushrooms
a type of basidiocarp (fruiting body)
Hyphae in this phylum have septa

71. Basidiomycete Fruiting Bodies

72. Basidiomycetes 2 Plasmogamy occurs Dikaryotic secondary mycelium forms
fusion of 2 hyphae of different mating types
Dikaryotic secondary mycelium forms
Basidiocarp develops
basidia form

73. Basidiomycetes 3 Karyogamy occurs Meiosis produces 4 haploid nuclei
producing diploid zygote nucleus
Meiosis produces 4 haploid nuclei
become basidiospores
When basidiospores germinate
form haploid primary mycelia

74. Basidium with Basidiospores

75. Basidiospore Basidium 5 µm Fig. 26-16, p. 570
Figure 26.16: SEM of a basidium.
Each basidium produces four basidiospores.
5 µm
Fig , p. 570

76. Basidiomycetes 4 Basidiomycetes include mushrooms puffballs
bracket fungi
rusts
smuts

77. Basidiomycete Life Cycle

78. Basidiospore Basidium 5 µm Fig. 26-16, p. 570
Figure 26.16: SEM of a basidium.
Each basidium produces four basidiospores.
5 µm
Fig , p. 570

79. Insert “Club fungus life cycle”
club_fungus_life_v2.swf

80. Explore fungus life cycles by clicking on the figures in ThomsonNOW.

81. KEY CONCEPTS
According to current hypotheses, fungi evolved from a unicellular, flagellate protist and diverged into five main groups

82. Learning Objective 7
What is the ecological significance of fungi as decomposers?

83. Decomposers Most fungi are decomposers break down organic compounds
dead organisms, leaves, garbage, wastes
into simpler nutrients that can be recycled

84. Learning Objective 8
What is the important ecological role of mycorrhizae?

85. Mycorrhizae 1
Mutualistic relationships between fungi and roots of plants
Fungus supplies water and nutrient minerals to plant
Plant secretes organic compounds needed by fungus

86. Mycorrhizae 2
Glomeromycetes form endomycorrhizal associations with roots
Ascomycetes and basidiomycetes form ectomycorrhizae with tree roots
do not penetrate root cells

87. Mycorrhizal Associations

88. Learning Objective 9
What is the unique nature of a lichen?

89. Lichen
Symbiotic combination of fungus and photoautotroph (alga or cyanobacterium)
Photoautotroph provides fungus with organic compounds, shelter, water, minerals
Lichens have 3 main growth forms: crustose, foliose, fruticose

90. Lichens

91. Fungal hyphae interwoven with photoautotroph
Soredia
Surface
layer
(fungal hyphae)
Fungal hyphae interwoven with photoautotroph
Figure 26.20: Lichens.
Loosely
woven hyphae
Bottom layer (fungal hyphae)
Rock or other surface
to which lichen is attached
Fig a, p. 573

92. Fruticose liche (Ramalina)
Crustose lichens (Bacidia, Lecanora)
Figure 26.20: Lichens.
Foliose lichen (Parmelia)
Fig b, p. 573

93. Insert “Lichens”
lichens.swf

94. Learn more about lichens by clicking on the figure in ThomsonNOW.

95. Learning Objective 10
How do fungi impact humans economically?

96. Useful Fungi Fungi are used as foods (mushrooms, morels, truffles)
in production of beer, wine, bread (yeasts)
to produce cheeses and soy sauce
to make citric acid and other industrial chemicals

97. Edible Ascomycetes

98. Learning Objective 11
What is the importance of fungi to biology and medicine?
How do fungi infect plants and humans?
Identify at least three fungal plant diseases and three fungal animal diseases

99. Research Fungi are model organisms for molecular biology and genetics
yeast Saccharomyces cerevisiae
other fungi
Biological control of insects
such as mosquitoes that transmit malaria

100. Medications Fungi are used to make medications
penicillin, other antibiotics

101. Pathogens Fungi are opportunistic pathogens in humans ringworm
athlete’s foot
candidiasis
histoplasmosis

102. Toxins Some fungi produce mycotoxins such as aflatoxins
cause liver damage and cancer

103. Fungal Plant Diseases Fungal hyphae infect plants through stomata
hyphal branches (haustoria) penetrate plant cells
obtain nourishment from cytoplasm
Include
wheat rust
Dutch elm disease
chestnut blight

104. Fungal Infection of Plants

105. Spore Hypha Epidermis Stoma Airspace Leaf Haustoria Fig. 26-23, p. 576
Figure 26.23: How a fungus parasitizes a plant.
In this example, the hypha enters the leaf through a stoma. The hypha grows, branching extensively through the internal air spaces, and penetrates plant cells with specialized hyphal extensions called haustoria.
Haustoria
Fig , p. 576

106. Fungal Plant Diseases

107. KEY CONCEPTS
Fungi are of major ecological, economic, biological, and medical importance