1. Chapter 31
Fungi

2. YOU MUST KNOW
The characteristics of fungi.
Important ecological roles of fungi in mycorrhizal associations, and as decomposers and parasitic plant pathogens.
The major clades of fungi.

3. 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

4. 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

5. 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

6. 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

7. 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

8. (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

9. 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.

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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 16

17. 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

18. 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 18

19. 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). 19

20. 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 20

21. Sac Fungi - Ascomycota CUP FUNGI (visible to the eye) YEASTS
(microscopic) 21

22. 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 22

23. Diversity of Club Fungi
PUFFBALL
EARTH STAR
MUSHROOM
SHELF FUNGI
BIRD’S NEST FUNGI
JELLY FUNGI 23

24. 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 24

25. 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 25

26. 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. 26

27. 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 27

28. 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 28

29. 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. 29

30. Symbiotic Fungi
lichen
mycorrhizae 30

31. 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

32. 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

33. 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 33

34. 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. 34

35. 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. 35

36. 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 36

37. 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

38. (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

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

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

41. A Review of Fungal Phyla
Table 31.1