1. Biology, 9th ed,Sylvia Mader
Chapter 23
Chapter 23
The Fungi
The Fungi

2. Symbiotic Relationships
Outline
Characteristics
Structure
Reproduction
Evolution
Sac Fungi
Yeasts
Club Fungi
Smuts and Rusts
Imperfect Fungi
Symbiotic Relationships

3. Characteristics of the Fungi
Kingdom Fungi contains 80,000 spp
Mostly multicellular eukaryotes that share a common mode of nutrition
Heterotrophic
Cells release digestive enzymes and then absorb resultant nutrient molecules
Some are parasitic
Several have mutualistic relationship

4. Cell walls of chitin, like insect exoskeleton
Structure of Fungi
Body (thallus) of most fungi is multicellular mycelium (yeasts are unicellular)
Consists of a vast network of thread-like hyphae
Septate fungi have hyphae with cross walls
Nonseptate fungi are multinucleated
Hyphae grow from tip
Give the mycelium a large surface area per unit volume
Cell walls of chitin, like insect exoskeleton
Excess food stored as glycogen as in animals
Possibly evolved from red algae - both lack flagella

5. Mycelia and Hyphae of Fungi

6. Both sexual (in most) and asexual reproduction
Reproduction of Fungi
Both sexual (in most) and asexual reproduction
Sexual reproduction involves three stages:
Haploid Hyphae
Dikaryotic Stage
Diploid Zygote

7. Reproduction of Fungi
During sexual reproduction, hyphae from two different mating types fuse
Hyphae that contain paired haploid nuclei are said to be dikaryotic
Nuclear fusion produces diploid nucleus, which produces haploid windblown spores by meiosis
Spores germinate directly into haploid hyphae without embryological development
Asexual reproduction usually involves the production of windblown spores
Unicellular yeasts reproduce by budding

8. Dispersal of Spores

9. Diversity of Fungi: Zygomycota
Zygospore Fungi
Phylum Zygomycota
Mainly saprotrophs decomposing animal and plant remains
Black bread mold - Rhizopus stolonifer

10. Black Bread Mold, Rhizopus stolonifer

11. Diversity of Fungi: Zygomycota
Life cycle
Hyphae of opposite mating types grow toward each other
Hyphae swell at tips; cross walls develop behind each end; form gametangia
Gametangia merge resulting in a large multi-nucleate cell
Nuclei of the two mating types pair and then fuse
A thick wall develops around the zygospore
The zygospore becomes dormant for period
Sporangiophore(s) then sporangia develop, spores released
Spores dispersed by air currents; germinate into mycelia

12. Diversity of Fungi: Sac Fungi
Phylum Ascomycota - about 60,000 species of sac fungi
Most are saprotrophs that digest resistant materials containing cellulose, lignin, or collagen
Most are composed of septate hyphae
Neurospora, experimental organism for the one-gene-one-enzyme studies
Morels and truffles, famous gourmet delicacies revered throughout the world
Many plant diseases: Powdery mildews; leaf curl fungi; ergot of rye; chestnut blight and Dutch elm disease
Aspergillus and Candida cause serious human infections
Talaromyces (formerly Penicillium) is source of penicillin

13. Sac Fungi: Reproduction - Asexual
Life cycle
Asexual reproduction is the norm
Yeasts usually reproduce by budding
A small bulge forms on side of cell
Receives a nucleus and gets pinched off and becomes full size
The other ascomycetes produce spores called conidia or conidiospores
Vary in size and shape and may be multicellular
Conidia usually develop at the tips of conidiophores
Conidiophores differ in appearance and are diagnostic
Conidia are windblown
Conidia of Cladosporium cause allergies - concentrations of more than 35,000 conidia/m3 over Leiden (Germany)

14. Asexual Reproduction in Sac Fungi

15. Sac Fungi: Reproduction - Sexual
Life cycle, cont.
Sexual reproduction
Ascus refers to the fingerlike sac that develops during sexual reproduction
Asci usually surrounded and protected by sterile hyphae within an ascocarp
In cup fungi, ascocarps are cup-shaped
In morels they are stalked and are pitted like the surface of the moon
Haploid hyphae fuse to make diploid nucleus
Mitosis and then meiosis produces 8 ascospores

16. Sexual Reproduction in Sac Fungi

17. Black Mold

18. Tineas

19. Sac Fungi: Reproduction - Yeasts
Term “yeasts” is loosely applied to unicellular fungi, many of which are ascomycetes
Budding is common form of asexual reproduction
Sexual reproduction results in the formation of asci and ascospores
When some yeasts ferment, they produce ethanol and carbon dioxide

20. Diversity of Fungi: The Club Fungi
Phylum Basidomycota – 22,000 spp
Familiar toadstools, mushrooms, bracket fungi, puffballs, stinkhorns – some deadly poisonous
Also plant diseases such as the smuts and rusts
Mycelium composed of septate hyphae

21. The Club Fungi: Reproduction
Usually reproduce sexually
Haploid hyphae fuse, forming a dikaryotic (n + n) mycelium
Dikaryotic mycelium forms fruiting bodies called basidiocarps
Contain club-shaped structures called basidia
Nuclear fusion followed by meiosis produces basidiospores (up to 40,000,000 per hour)

22. Club Fungi

23. Club Fungi

24. The Club Fungi: Smuts and Rusts
Smuts and rusts are club fungi that parasitize cereal crops
Great economic importance because of annual crop losses
Do not form basidiocarps
Life cycle of rusts often requires two different plant host species
Black stem rust of wheat uses barberry bushes
Blister rust of white pine uses currant and gooseberry bushes
Eliminating these bushes in crop areas keeps rusts in check
Wheat rust
Controlled by breeding new resistant strains of wheat
Requires continuous development, because rust can mutate

25. Smuts & Rusts

26. Symbiotic Relationships: Lichens
Symbiotic association between a fungus and a cyanobacterium or green alga
Specialized fungal hyphae penetrate photosynthetic symbiont
Transfer nutrients directly to the fungus
Possibly mutualistic, but fungal symbiont probably a parasite of photosynthetic symbiont
Photosynthetic symbiont independent
Fungal symbiont usually can’t grow alone

27. Symbiotic Relationships: Lichens
Three morphological types
Compact crustose lichens - seen on bare rocks or on tree bark
Fruticose lichens – shrub-like
Foliose lichens - leaf-like
Can live in areas of extreme conditions and contribute to soil formation
Sensitive indicators of air pollution

28. Lichen Morphology

29. Symbiotic Relationships: Mycorrhizae
Mutualistic relationships between soil fungi and the roots of most familiar plants
Give plant greater absorptive surface
Help plants acquire mineral nutrients in poor soil
Fungal symbiont usually a sac fungus
Hyphae may enter cortex of root, but not cytoplasm
Ectomycorrhizae form a mantle that is exterior to the root, and they grow between cell walls.
Endomycorrhizae penetrate only the cell walls
Earliest fossil plants have mycorrhizae associated with them

30. Plant Growth Experiment

31. Symbiotic Relationships
Review
Characteristics
Structure
Reproduction
Evolution
Sac Fungi
Yeasts
Club Fungi
Smuts and Rusts
Imperfect Fungi
Symbiotic Relationships

32. Biology, 9th ed,Sylvia Mader
Chapter 23
Ending Slide Chapter 23
The Fungi
The Fungi