1. Kingdom Fungi The characteristics of fungi The evolution of the fungi
Fungal classification
Fungal life cycles

2. Introduction Fungi are eukaryotes
Nearly all multicellular (yeasts are unicellular)
Distinguished from other kingdoms by:
Nutrition
Structural organisation
Growth
Reproduction

3. Absorptive nutrition enables fungi to live as decomposers and symbionts
Fungi are heterotrophs that acquire nutrients by absorption
Secrete hydrolytic enzymes and acids to decompose complex molecules into simpler ones that can be absorbed
Specialised into three main types:
Saprobes - absorb nutrients from dead organic material
Parasitic fungi - absorb nutrients from cells of living hosts; some are pathogenic
Mutualistic fungi - absorb nutrients from a host, but reciprocate to benefit the host

4. Fungi as Saprobes and Decomposers

5. Fungi as Parasites & Pathogens

6. Fungi as Symbionts (Mutualism)

7. Extensive surface area and rapid growth adapt fungi for absorptive nutrition
Basic structural unit of fungal vegetative body (mycelium) is the hypha
Except for yeast, hyphae are organised around and within food source:
Composed of tubular walls containing chitin
Provide enormous surface area: 10cm2 of soil may contain 1km of hyphae with 314cm2 surface area

8. Fungal hyphae may be septate or aseptate
Hyphae of septate fungi are divided into cells by crosswalls called septa
Hyphae of aseptate fungi lack cross walls (coenocytic)
Parasitic fungi have modified hyphae called haustoria, which penetrate the host tissue but remain outside cell membrane

9. Fungi reproduce by releasing spores that are produced either sexually or asexually
Usually unicellular, haploid and of various shapes and sizes
Produced either sexually (by meiosis) or asexually (by mitosis)
In favourable conditions, fungi generally clone themselves by producing enormous numbers of spores asexually
For many fungi, sexual reproduction only occurs as a contingency - results in greater genetic diversity
Spores are the agent of dispersal responsible for geographic distribution of fungi:
Carried by wind or water
Germinate in moist places with appropriate substrata

10. Reproduce by spores Spores are reproductive cells Formed:
Sexual (meiotic in origin)
Asexual (mitotic in origin)
Formed:
Directly on hyphae
Inside sporangia
Fruiting bodies
Fungi reproduce by releasing spores that are produced either sexually or asexually.
The output of spores from one reproductive structure is enormous, with the number reaching into the trillions.
Dispersed widely by wind or water, spores germinate to produce mycelia if they land in a moist place where there is food.
Penicillium hyphae with conidia
Pilobolus sporangia
Amanita fruiting body

11. Generalised life cycle of fungi
Sexual
Asexual

12. Classification & Phylogeny
asci
basidia
The phyla of fungi are determined by
1. motility of spores
2. nature of sexual stage
Fungi moved onto land with the plants in the Early Paleozoic
Much of the evolution of fungi was in conjunction with the evolution of plants and plant parts
For example, when roots evolved, fungi were there and helped (mycorrhizas)
When wood evolved, fungi evolved to take advantage of it
Other evolutionary changes related to animals
zygosporangia
Classification & Phylogeny
motile spores

13. Phylum Chytridiomycota: chytrids may provide clues about fungal origins
Originally placed in Kingdom Protista
Share many characteristics with fungi:
Absorptive nutrition
Chitin cell walls
Hyphae
Enzymes / metabolism
Earliest fungi: evolved from protists and retained flagella

14. Phylum Zygomycota Characterised by dikaryotic zygosporangia
Mostly terrestrial - live in soil or decaying material
Some form mycorrhizae, mutualistic associations with plant roots
Hyphae are coenocytic - septa only found in reproductive cells
Some are pathogens

15. Mycorrhizae Specific, mutualistic association of plant roots and fungi
Fungi increase absorptive surface of roots and exchange soil minerals
Found in 95% of vascular plants
Necessary for optimal plant growth

16. Life cycle of the zygomycete Rhizopus stolonifer, a common bread mould

17. Life cycle of the zygomycete Rhizopus stolonifer, a common bread mould
Under favourable conditions, reproduces asexually:
Sporangia develop at tips of hyphae
Mitosis produces hundreds of haploid spores
In unfavourable conditions, sexual reproduction occurs:
Mycelia of opposite mating types (+ and -) for gametangia that contain several haploid nuclei walled off by the septum
Plasmogamy of gametangia occurs  dikaryotic zygosporangium
Under favourable conditions, karyogamy occurs: diploid nuclei immediately undergo meiosis producing haploid spores
Zygosporangium germinates sporangium which releases recombined haploid spores

18. Phylum Ascomycota: sac fungi produce sexual spores in saclike asci
Include unicellular yeasts and complex multicellular cup fungi
Hyphae are septate
In asexual reproduction, tips of specialised hyphae form conidia - chains of haploid asexual spores
In sexual reproduction, haploid mycelia of opposite mating strains fuse

19. Life cycle of an ascomycete
ASEXUAL
SEXUAL
MITOSIS

20. Sac fungi diversity
This begins the first of several photographic reviews of fungal diversity. Enjoy the pictures and try and get a feeling of some of the different forms these fungi take and their roles in the environment.

21. Phylum Basidiomycota: club fungi
Named after transient diploid stage: basidium
Important decomposers of wood / plant material
Include:
Mycorrhiza-forming mutualists
Mushroom-forming fungi
Plant parasites e.g. rusts and smuts
Characterised by dikaryotic mycelium that reproduces sexually via basidiocarps

22. Life cycle of a mushroom-forming basidiomycete

23. Life cycle of a mushroom-forming basidiomycete
Haploid basidiospores grow into short-lived haploid mycelia: under certain conditions, plasmogamy occurs
Resulting dikaryotic mycelium grows forming mycorrhiza or mushrooms (basidiocarps)
Mushroom cap supports and protects gills: karyogamy in the terminal, dikaryotic cells lining the gills produces diploid basidia
Resulting basidium immediately undergoes meiosis producing four haploid basidiospores
Asexual reproduction less common than in ascomycetes

24. Phylum Deuteromycota The “Imperfect Fungi”
Fungi that seldom or never reproduce sexually.
Asexual reproduction by vegetative growth and production of asexual spores common.

25. Moulds Rapidly growing fungus with no sexual stages
May develop into a sexual fungus, producing zygosporangia, ascocarps or basidiocarps
Moulds with no known sexual stage are known as Deuteromycota or imperfect fungi:
Penicillium
Flavour for blue cheeses

26. Yeasts Unicellular: reproduce
Asexually by budding
Sexually by producing asci or basidia
Saccharomyces cerevisiae is most important domesticated fungus:
Baking and brewing
Model organism
Can cause problems:
Rhodotorula: shower curtains
Candida: “thrush”
Adapted to liquids

27. Lichens Symbiosis of algae with fungal hyphae The alga:
Provides fungus with food
May fix nitrogen
Fungus provides good environment for growth:
Hyphal mass absorbs minerals and protects algae
Produces compounds that:
shield algae from sunlight
are toxic - prevents predation

28. Lichen reproduction Occurs as a combined unit or independently
Fungi reproduce sexually (usually ascocarps)
Algae reproduce asexually by cell division
Symbiotic units reproduce asexually by:
Fragmentation of parent
Formation of soredia: small clusters of hyphae with embedded algae

29. HUMAN-FUNGUS INTERACTIONS
Beneficial Effects of Fungi
Decomposition - nutrient and carbon recycling.
Biosynthetic factories. Can be used to produce drugs, antibiotics, alcohol, acids, food (e.g., fermented products, mushrooms).
Model organisms for biochemical and genetic studies.
Harmful Effects of Fungi
Destruction of food, lumber, paper, and cloth.
Animal and human diseases, including allergies.
Toxins produced by poisonous mushrooms and within food (e.g., grain, cheese, etc.).
Plant diseases.