1. Chapter 31
Fungi

2. Mighty Mushrooms 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
Figure 31.1

3. Characteristics of Fungi
Fungi are heterotrophs that feed by absorption
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
Fungi exhibit diverse lifestyles
Decomposers
Parasites
Mutualistic symbionts

4. The morphology of multicellular fungi
Body Structure
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

5. Body Structure
Except for yeasts, ALL fungi are multi-cellular and composed of tiny filaments called hyphae.
The bodies of multicellular fungi are composed of many hyphae tangled together into a thick mass called a mycelium.
The mycelium is well suited to absorb food.
The fruiting body is a reproductive structure that develops from a mycelium that grows below the surface of the ground.
Most fungi have cell walls made of chitin

6. Body Structure Some fungi Coenocytic 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
Septum
Nuclei
Figure 31.3a, b
(a) Septate hypha
(b) Coenocytic hypha

7. (a) Hyphae adapted for trapping and killing prey
Body Structure
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
Fungal hypha
Plant cell wall
Plant cell
Plant cell plasma membrane
(b) Haustoria
Haustorium
Figure 31.4a, b

8. Mycorrhizae Mycorrhizae
Are mutually beneficial relationships between fungi and plant roots
A symbiotic associations of plant roots and fungi.
Fungi increases the surface area of the plants roots.
Its presence is often necessary for the growth of many plants.

9. Fungi produce spores through sexual or asexual life cycles
Life Cycles of Fungi
Fungi produce spores through sexual or asexual life cycles
Fungi propagate themselves
By producing vast numbers of spores, either sexually or asexually

10. The Generalized Life Cycle of Fungi
Key
Haploid (n)
Heterokaryotic
(unfused nuclei from
different parents)
Diploid (2n)
PLASMOGAMY
(fusion of cytoplasm)
stage
KARYOGAMY
(fusion of nuclei)
SEXUAL
REPRODUCTION
Spore-producing
structures
Spores
ASEXUAL
Zygote
Mycelium
GERMINATION
MEIOSIS
Figure 31.5

11. Sexual Reproduction in Fungi
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

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

13. Yeasts
Other asexual fungi are yeasts that inhabit moist environments which produce by simple cell division
Many molds and yeasts have no known sexual stage
Mycologists have traditionally called these deuteromycetes, or imperfect fungi
10 m
Parent cell
Bud
Figure 31.7

14. Evolution 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

15. Fungi were among the earliest colonizers of land
The Move to Land
Fungi were among the earliest colonizers of land
Probably as symbionts with early land plants
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

16. Arbuscular mycorrhizal fungi
The Phylogeny of Fungi
Chytrids
Zygote fungi
Arbuscular mycorrhizal fungi
Sac fungi
Club fungi
Chytridiomycota
Zygomycota
Glomeromycota
Ascomycota
Basidiomycota
Figure 31.9

17. Classification of Fungi
Fungi are classified according to their structure and method of reproduction
The 5 main groups of fungi are:
Chytridiomycota (spore fungi)
Motile spores with flagella
Zygomycota (common molds)
Bread molds
Ascomycota (sac fungi)
Club fungi, yeasts
Basidiomycota (club fungi)
mushrooms
Deuteromycota (imperfect fungi)
“catch all”, penicillium 17

18. Chytrids
Fungi classified in the phylum Chytridiomycota, or chytrids are found in freshwater and terrestrial habitats
Can be saprobic or parasitic
Chytrids are unique among fungi in having flagellated spores, called zoospores
25 m
4 m
Hyphae
Flagellum
Figure 31.10

19. Zygomycota – The Common Molds
Zygomycetes are the familiar molds that grown on meat, cheese, and bread.
Ex: Rhizopus stolonifer (black bread mold).
3 Types of Hyphae:
Stolons: Stem like hyphae - run along top of food source
Rhizoids: Root like hyphae – Penetrate & release digestive enzymes, absorb organic matter
Sporangiophores : hyphae that push up in air…release spores into the air 19

20. 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
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
Mating type (+)
Mating type ()
Gametangia with haploid nuclei
50 m
Sporangia
A heterokaryotic zygosporangium forms, containing multiple haploid nuclei from the two parents. 3
The spores germinate and grow into new mycelia. 8 9
Mycelia can also reproduce asexually by forming sporangia that produce genetically identical haploid spores.
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.
Figure 31.12

21. Some zygomycetes, such as Pilobolus
Can actually “aim” their sporangia toward conditions associated with good food sources
0.5 mm
Figure 31.13

22. Ascomycota – The Sac Fungi
The phylum Ascomycota is named for the ascus, a reproductive structure that contains spores.
Ascomycetes are the largest phyum in the kingdom Fungi
Some are large and some are microscopic.
Examples: cup fungi (large) and yeasts (microscopic). 22

23. Phylum Ascomycota - Sac Fungi
Named for the Ascus (reproductive structure that contains spores)
Visible and microscopic
Sexual and Asexual Reproduction
Conidia – tiny spore; name means “dust”
Formed at tips of specialized Hyphae called Conidiophore.
In suitable conditions form new haploid organisms. 23

24. Life Cycle of Neurospora crassa – an Ascomycete
Ascomycete mycelia can also reproduce asexually by producing haploid conidia. 7
Dispersal
ASEXUAL REPRODUCTION
Germination
Mycelium
Conidiophore
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)
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 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).
The diploid nucleus divides by meiosis, yielding four haploid nuclei. 4
Figure 31.17

25. Phylum Ascomycota - Yeast
Yeasts are Unicellular fungi
Have ascus and produce ascospores
Dry granules are ascospores!
Activate in moist conditions
Can see asexual reproduction
Baking Yeast – called Saccharomyces
Means “sugar fungi”
use alcohol fermentation to obtain energy
Sugar used as food, give off alcohol, CO2
CO2 is why bread rises 25

26. Sac Fungi - Ascomycota CUP FUNGI (visible to the eye) YEASTS
(microscopic) 26

27. Basidiomycota – The Club Fungi
The phylum Basidiomycota gets its name from a specialized reproductive structure (called a basidium) that resembles a club.
Includes:
Mushrooms
Shelf fungi
Puffballs
Earthstars
Jelly fungi
Plant rusts
Bird’s nest fungi 27

28. Diversity of Club Fungi
PUFFBALL
EARTH STAR
MUSHROOM
SHELF FUNGI
BIRD’S NEST FUNGI
JELLY FUNGI 28

29. Phylum Basidiomycota - Club Fungi
Reproductive Structure looks like a club
Fruiting Body
Common Mushrooms
Edible, Medicinal, Poisonous
Very complex life cycle
Mycelium underground grow very large and survive a long time
Largest organism in the world is a club fungi 29

30. Life Cycle Fruiting bodies are the visible mushrooms
Produced by vast underground networks of mycelium (bundles of hyphae) when ready to reproduce
Gills – part on mushroom which contain Basidia
Basidia have 2 nuclei fuse to make 2N zygote cell
Zygote undergoes meiosis making Basidiospores which are scattered
Mating types (+) and (-) can fuse sexually to make secondary mycelium network 30

31. Life Cycle of a Mushroom-Forming Basidiomycete
A dikaryotic mycelium forms, growing faster then, and ultimately crowding out, the haploid parental mycelia. 2
Two haploid mycelia of different mating types undergo plasmogamy. 1
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) 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).
In a suitable environment, the basidiospores germinate and grow into short-lived haploid mycelia. 8
When mature, the basidiospores are ejected, fall from the cap, and are dispersed by the wind. 7
The basidiocarp gills are lined with terminal dikaryotic cells called basidia. 4
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
Karyogamy in the basidia produces diploid nuclei, which then undergo meiosis. 5
Figure 31.20

32. 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

33. Deuteromycota – The Imperfect Fungi
Deuteromycota is an extremely varied phylum composed of those fungi that are not placed in other phyla.
The term imperfect implies that these fungi do not appear to have sexual reproduction.
Ex: Penicillium notatum – the source of antibiotic penicillin. 33

34. Phylum Deuteromycota - Imperfect Fungi
Extremely varied Phylum
Grab Bag – whatever does not fit in others
NEVER have observed Sexual Life Cycle
Reproduce Asexually by Conidia spores
Like Ascomycetes
Ex: Penicillium notatum
Grows on fruit
Source of antibiotic penicillin 34

35. Fungi are heterotrophic decomposers
Ecology of Fungi
Fungi are heterotrophic decomposers
Saprobes – fungi that obtain food by breaking down dead and decaying orgs
Can be decomposers – good for nutrient cycle
Need this to maintain life!
Can be “predators”
Some fungi poison and decompose worms which feed on them 35

36. Ecology of Fungi - Symbiosis
Lichens
A symbiotic associations between a fungus and a photosynthetic organism.
Lichen can grow on dry, bare rock and are often the first organisms to inhabit an area (pioneer species).
The lichen break down the bare rock, allowing other plants to grow.
Mycorrhizae
A symbiotic associations of plant roots and fungi.
Fungi increases the surface area of the plants roots.
Its presence is often necessary for the growth of many plants. 36

37. Symbiotic Fungi
lichen
mycorrhizae 37

38. Lichens
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

39. Mycorrhizae Mycorrhizae
Are enormously important in natural ecosystems and agriculture
Increase plant productivity
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.
EXPERIMENT
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.
Figure 31.21
RESULTS
RESULTS

40. Disease: Some Fungi are Pathogenic
Ecology of Fungi
Some produce antibiotics – Penicillium makes penicillin (discovered by Alexander Fleming)
Disease: Some Fungi are Pathogenic
Plant diseases – “Rusts”, Root Rot
Animal diseases - Ringworm, Yeast infections, Athlete’s Foot 40

41. Fungi as Heterotrophs
ALL FUNGI ARE HETEROTROPHS – BUT THEY OBTAIN NUTRIENTS IN VARIOUS WAYS:
Many are saprobes, organisms that obtain food from decaying organic matter.
Some are parasites which harm other organisms.
Some are symbionts that live in close and mutually beneficial association with other species. 41

42. Fungi as Decomposers
Fungi are found in every ecosystem, where they recycle nutrients by breaking down the bodies and wastes of other organisms.
Without decay, the energy-rich compounds that organisms accumulate during their lifetime would be lost forever. 42

43. Parasitic fungi cause serious plant and animal diseases:
Fungi as Parasites
Parasitic fungi cause serious plant and animal diseases:
wheat rust
mildew on fruit
athlete’s foot 43

44. Fungal Impact on Ecosystems
Fungi have a powerful impact on ecosystems and human welfare
Fungi are well adapted as decomposers of organic material
Performing essential recycling of chemical elements between the living and nonliving world
Fungi form symbiotic relationships with
Plants, algae, and animals
Some fungi share their digestive services with animals
Helping break down plant material in the guts of cows and other grazing mammals

45. (b) Tar spot fungus on maple leaves
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

46. Practical Uses of Fungi
Humans eat many fungi
And use others to make cheeses, alcoholic beverages, and bread

47. Fungi and Antibiotics
Antibiotics produced by fungi can be used to treat bacterial infections
Staphylococcus
Penicillium
Zone of inhibited growth
Figure 31.26

48. A Review of Fungal Phyla
Table 31.1