1. Chapter 22 Fungi
(Sections ) 1

2. 22.1 High-Flying Fungi
Fungi produce microscopic spores that winds can disperse long distances
As a result, it is difficult to prevent the spread of a fungal pathogen, such as wheat stem rust
A new strain of wheat stem rust, Ug99, is able to infect most wheat varieties that were previously considered resistant

3. Wheat Stem Rust
An infection begins when a spore lands on a wheat plant and fungal filaments invade the plant through its stomata

4. 22.2 Fungal Traits and Diversity
Like animals, fungi are heterotrophs
Unlike animals, fungi have walled cells and digest food outside their body
fungus
Eukaryotic heterotroph with cell walls of chitin
Obtains nutrients by digesting them outside the body and absorbing them

5. Structure and Function
Most fungi are saprobes that feed on organic remains
They serve as essential decomposers in most ecosystems
Other fungi live in or on organisms
They may be harmless, beneficial, or parasitic
saprobe
Organism that feeds on wastes and remains

6. Structure and Function (cont.)
Fungi include single-celled yeasts and multicelled species
They disperse by releasing spores
In multicelled species, spores germinate and give rise to filaments (hyphae) which typically grow as an extensive mesh called a mycelium

7. Key Terms hypha Component of a fungal mycelium
A filament made up of cells arranged end to end
There may or may not be cross-walls (septa) between cells of a hypha
mycelium
Mass of threadlike filaments (hyphae) that make up the body of a multicelled fungus

8. Examples of Multicelled Fungi
Green mold on grapefruit
Scarlet hood mushroom
Figure 22.1 Examples of multicelled fungi.

9. Mycelium
Close-up of a mycelium, showing threadlike hyphae, each consisting of cells arranged end to end

10. Mycelium one cell of a hypha in the mycelium
Figure 22.2 Close-up of a mycelium, showing the threadlike hyphae, each consisting of cells arranged end to end.
one cell of a hypha
in the mycelium
Fig. 22.2, p. 344

11. Life Cycles In fungi, only the zygote is diploid
Spores may form by mitosis (asexual spores) or by meiosis (sexual spores)
Depending on the group, cells of a hyphae may be haploid (n) or dikaryotic (n+n)
dikaryotic
Having two genetically distinct nuclei

12. Fungal Diversity
In early lineages (chytrids, glomeromycetes, zygote fungi), hyphae have few or no cross-walls (septa)
More recently evolved lineages (sac fungi, club fungi) have hyphae with porous crosswalls at regular intervals
In all groups, water and nutrients move freely between cells of a hypha

13. Key Concepts Traits and Classification
Fungi are single-celled and multicelled heterotrophs that feed by secreting digestive enzymes onto organic matter, then absorbing the released nutrients
Multicelled species form a mesh of absorptive filaments
In the most diverse groups, cross-walls reinforce the filaments

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15. 22.3 Chytrids, Zygote Fungi, and Relatives
Chytrids, zygote fungi, and glomeromycetes are the oldest and least diverse groups of fungi
chytrid
Fungus that makes flagellated spores
zygote fungus
Fungus that forms a zygospore during sexual reproduction
glomeromycete
Fungus with hyphae that grow inside the wall of a plant root cell

16. Chytrids
The oldest fungal lineage, the chytrids are a mostly aquatic group and the only fungi with flagellated spores
Chytrids include aquatic decomposers, some that digest cellulose in herbivore guts, and parasites
Parasitic chytrid infections are pushing some frog species to extinction

17. Zygote Fungi (Zygomycetes)
Zygote fungi include familiar molds that grow on fruits, breads, and other foods
Their hyphae are continuous tubes that have no cross-walls
Sexual reproduction produces a thick-walled zygospore
Zygote fungi also produce asexual spores on specialized hyphae

18. Life Cycle of a Zygote Fungus
1. Black bread mold (Rhizopus) reproduces asexually as it grows through a slice of bread
2. Sexual reproduction begins when hyphae of two different mating strains meet
3. Cytoplasmic fusion of hyphal cells yields an immature zygospore that is dikaryotic
4. Fusion of the zygospore’s haploid nuclei produces the mature diploid zygospore
5. The zygospore undergoes meiosis, germinates, and produces an aerial hypha with haploid spores at its tip; each spore can give rise to a new mycelium

19. Life Cycle of a Zygote Fungus

20. Life Cycle of a Zygote Fungus
mature
zygospore 4
Diploid (2n)
Fusion of nuclei
Meiosis
Dikaryotic
(n+n)
Haploid (n) 5
spores
young zygospore 3
Cytoplasmic fusion
Figure 22.3 Life cycle of a zygote fungus, the black bread mold (Rhizopus).
mycelium 1
asexual
reproduction 2
Fig. 22.3, p. 345

21. Life Cycle of a Zygote Fungus
Diploid (2n)
mature
zygospore 4
Meiosis
Haploid (n)
spores 5
young zygospore
Fusion of nuclei
Dikaryotic
(n+n) 3
asexual
reproduction
mycelium 1
Cytoplasmic fusion 2
Figure 22.3 Life cycle of a zygote fungus, the black bread mold (Rhizopus).
Stepped Art
Fig. 22.3, p. 345

22. ANIMATION: Zygomycete life cycle
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23. Glomeromycetes
Glomeromycetes live in soil and extend their hyphae into plant roots
The hyphae branch inside plant cell walls and deliver nutrients to the cell and take up plant sugars
Figure 22.4 Glomeromycete hypha branching inside a root cell wall.

24. Key Concepts The Oldest Lineages
The oldest fungal lineages have filaments with few or no cross-walls
The mostly aquatic chytrid fungi make flagellated spores
Zygote fungi make thick-walled zygotes that release sexual spores
Glomeromycetes are fungi that branch inside plant cell walls

25. 22.4 Sac Fungi Sac fungi are the most diverse fungal group
They include single-celled yeasts and multicelled species such as cup fungi and morels
sac fungi
Most diverse fungal group; sexual reproduction produces ascospores inside a saclike structure (an ascus)

26. Life Cycle Sac fungi produce sexual spores in asci
In multicelled species, these saclike structures form on an ascocarp, a fruiting body composed of haploid and dikaryotic hyphae that have internal cross-walls at regular intervals

27. Sac Fungus Fruiting Bodies
The cup of the scarlet cup fungus is an ascocarp
Asci, each containing eight ascospores (sexual spores) form on the cup’s inner surface
Figure 22.5 Sac fungus fruiting bodies (ascocarps). A The cup of the scarlet cup fungus is an ascocarp. Asci, each containing eight ascospores (sexual spores) form on the cup’s inner surface. B Morels and C truffles are edible ascocarps. Morels develop aboveground. Truffles form underground.

28. A Sampling of Diversity
Yeasts that are sac fungi help us make wine, breads, and alcoholic beverages
The antibiotic penicillin was originally isolated from a mold (Penicillium) that is a sac fungus
Related molds are used to flavor cheeses

29. Edible Ascocarps Morels and truffles are edible ascocarps
Morels develop aboveground
Truffles form underground
Figure 22.5 Sac fungus fruiting bodies (ascocarps). A The cup of the scarlet cup fungus is an ascocarp. Asci, each containing eight ascospores (sexual spores) form on the cup’s inner surface. B Morels and C truffles are edible ascocarps. Morels develop aboveground. Truffles form underground.

30. A Predatory Sac Fungus
Arthrobotrys captures and feeds on roundworms; rings on the hyphae constrict and entrap the worms, then hyphae grow into the captive and digest it

31. A Predatory Sac Fungus part of one hypha that forms a nooselike ring
roundworm
Figure 22.6 A predatory fungus (Arthrobotrys) that captures and feeds on roundworms. Rings on the hyphae constrict and
entrap the worms, then hyphae grow into the captive and digest it.
Fig. 22.6, p. 346

32. VIDEO: Predatory Fungus32

33. Key Concepts
Sac Fungi
Sac fungi, the most diverse fungal lineage, include single cells such as yeasts used in baking, and multicelled species that have filaments reinforced with cross-walls
When sac fungi reproduce sexually, they produce spores inside a saclike structure

34. 22.5 Club Fungi
Like sac fungi, multicelled club fungi have hyphae with cross- walls; they can produce complex fruiting bodies (basidiocarps) such as mushrooms
Club fungi are the only fungi that can break down lignin in wood, and are important as decomposers in forest habitats
club fungi
Fungi that produce spores in club-shaped cells

35. Club Fungus Fruiting Bodies

36. Club Fungus Fruiting Bodies
Figure 22.7 Club fungus fruiting bodies (basidiocarps).
Puffball
Fig. 22.7a, p. 347

37. Club Fungus Fruiting Bodies
Figure 22.7 Club fungus fruiting bodies (basidiocarps).
Shelf fungus
Fig. 22.7b, p. 347

38. Club Fungus Fruiting Bodies
Figure 22.7 Club fungus fruiting bodies (basidiocarps).
Coral fungus
Fig. 22.7c, p. 347

39. Club Fungus Fruiting Bodies
Figure 22.7 Club fungus fruiting bodies (basidiocarps).
Chanterelles
Fig. 22.7d, p. 347

40. Club Fungus Life Cycle
1. Haploid hyphal cells meet; cytoplasm fuses and forms a dikaryotic (n+n) cell
2. Mitotic cell divisions form a mycelium; produces a mushroom
3. Spore-making cells form at edges of the mushroom’s gills
4. Inside these dikaryotic cells, nuclei fuse, producing diploid (2n) cells
5. Diploid cells undergo meiosis, forming haploid (n) spores
6. Spores are released; give rise to a new haploid mycelium

41. Club Fungus Life Cycle

42. Club Fungus Life Cycle zygote Diploid (2n) Fusion of nuclei Meiosis4
zygote
Diploid (2n)
Fusion of nuclei
Meiosis
Dikaryotic
(n+n)
Haploid (n) 5
spore (n) 3
gill
cap 6
stalk
Figure 22.8 Club fungus life cycle. Different mating strains are indicated here by red or blue nuclei. The photo at lower left shows spores at the edge of gills 1 2
Cytoplasmic
fusion
Fig. 22.8, p. 347

43. Club Fungus Life Cycle zygote Diploid (2n) Fusion of nuclei Meiosis
Haploid (n)
Cytoplasmic fusion
Dikaryotic (n+n)
cap
stalk
gill 1 2
zygote
Fusion of nuclei
Diploid (2n) 4 3 6
Meiosis 5
spore (n)
Figure 22.8 Club fungus life cycle. Different mating strains are indicated here by red or blue nuclei. The photo at lower left shows spores at the edge of gills
Answer: dikaryotic.
Stepped Art
Fig. 22.8, p. 347

44. ANIMATION: Club fungus life cycle
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45. Key Concepts Club Fungi Most club fungi are multicelled
Like the closely related sac fungi, they have filaments reinforced with cross walls
Sexual reproduction involves formation of spores in club- shaped cells
A mushroom is an example of a club fungus fruiting body

46. 22.6 Fungi as Partners
Many fungal species are symbiotic with photosynthetic cells in lichens, while others are symbionts that live in or on plants
lichen
Composite organisms, consisting of a fungus and a single celled alga or a cyanobacterium
mycorrhiza
Mutually beneficial partnership between a fungus and a plant root

47. Lichens
A lichen is a composite organism composed of a fungus and photosynthetic cells of a green alga or cyanobacterium
A lichen may be a mutualism or the fungus may be parasitically exploiting captive photosynthetic cells
mutualism
Mutually beneficial relationship between two species

48. Lichens (cont.)
The fungus makes up the bulk of the lichen body and obtains a supply of nutrients from its photosynthetic partner
Lichens disperse by releasing fragments that include cells of both partners – the fungus also produces spores
Lichens are important as pioneers in new habitats; they facilitate the breakdown of rock to form soil

49. Lichens

50. Lichens dispersal fragment (cells of fungus and of
photosynthetic species)
outer layer
of fungal cells
photosynthetic
species
inner layer of
loosely woven
hyphae
outer layer
of fungal cells A B
Figure 22.9 Lichens. A Leaflike lichen on a birch tree. B Cross-section of a leaflike lichen. C Encrusting lichens on granite. C
Fig. 22.9, p. 348

51. Lichens
Figure 22.9 Lichens. A Leaflike lichen on a birch tree. B Cross-section of a leaflike lichen. C Encrusting lichens on granite.
Fig. 22.9a, p. 348

52. Lichens
Figure 22.9 Lichens. A Leaflike lichen on a birch tree. B Cross-section of a leaflike lichen. C Encrusting lichens on granite.
Fig. 22.9b, p. 348

53. Lichens dispersal fragment (cells of fungus and of
photosynthetic species)
outer layer
of fungal cells
photosynthetic
species
Figure 22.9 Lichens. A Leaflike lichen on a birch tree. B Cross-section of a leaflike lichen. C Encrusting lichens on granite.
inner layer of
loosely woven
hyphae
outer layer
of fungal cells B
Fig. 22.9b, p. 348

54. Lichens
Figure 22.9 Lichens. A Leaflike lichen on a birch tree. B Cross-section of a leaflike lichen. C Encrusting lichens on granite.
Fig. 22.9c, p. 348

55. ANIMATION: Lichens 55

56. Mycorrhizae: Fungus + Roots
Most plants have mycorrhizae (mutualism between a plant root and a fungus) and grow better with them
Fungal hyphae surround or penetrate the roots and supplement the root’s absorptive surface area
The fungus shares absorbed mineral ions with the plant and gets some photosynthetic sugars in return

57. Mycorrhiza

58. Mycorrhiza young root hyphal strands A
Figure A Mycorrhiza formed by a fungus and young hemlock tree root. B Experimental demonstration of the effects of mycorrhizae on plant growth in phosphorus-poor, sterilized soil. Seedlings at left were grown without a fungus. Seedlings at right, the experimental group, were grown with a partner fungus. A
Fig a, p. 348

59. Effects of Mycorrhizae
Seedlings grown without and with a partner fungus

60. Key Concepts Interactions With Other Organisms
Some fungi partner with photosynthetic cells as lichens
Others live in or on plant roots and benefit the plant by sharing nutrients
A minority of fungi are parasites
Some of these cause diseases in plants or in humans

61. 22.7 Fungi as Pathogens
Some fungi are pathogens that attack living plants or animals
Fungi that feed on plants can be ecologically and economically important
In humans, fungal infections usually involve the skin, or are inhaled

62. Plant Pathogens
Fungal pathogens cause wheat stem rust, powdery mildew of roses, and killed American chestnuts
One sac fungus that infects cereal grains makes a toxin that causes ergotism, a type of food poisoning that causes hallucinations, hysteria, and convulsions

63. Ergotism
Grains of rye with spore-bearing structures of Claviceps purpurea
Eating grain infected by this species causes ergotism
Figure Grains of rye with spore-bearing structures of Claviceps purpurea. Eating grain infected bythis species causes a type of food poisoning called ergotism.

64. Human Pathogens
Inhaled fungal spores can cause histoplasmosis or coccidioidomycosis, which can be fatal to people with a weakened immune system
Fungal skin infections include “athletes foot” and “ringworm”
Yeast infections of the vagina are also common

65. “Athlete's Foot”
Fungal skin infections include “athletes foot”

66. High-Flying Fungi (revisited)
In 2006, sac fungus spores (Fusarium) in contact lens solution caused eye infections that resulted in cornea surgery for many patients
Fusarium species have been found in air samples collected using remote-controlled model aircraft