1. Warm up What do you think is the largest living organism on Earth?
Armillaria ostoyae (honey mushroom)
at least 2,400 years old
How large do you think it is?
covers 2,200 acres (3.5 miles across, 3 feet deep)
about 1,665 football fields

2. Kingdom Fungi The characteristics of fungi Fungal life styles
This smaller-sized file version lacks the photographic reviews of fungal diversity and only has the “main” slides
All photographsin this presentation © Pearson Education or Fred M. Rhoades

3. The Characteristics of Fungi
Fungi are NOT plants
Most multicellar, some unicellular (yeast)
Hyphae = tubular units of construction, made of chitin
Heterotrophic by absorption
Reproduce by spores
Ecologically pivotal roles

4. Hyphae Slender tubes Hard wall of chitin
Crosswalls may form compartments (± cells)
Multinucleate
Grow at tips
Chitin is the same material used by Arthropods (Insects, crabs, etc.) in their exoskeletonsa
Nuclei of fungi are hard to see without stains

5. Heterotrophic by Absorption
Fungi get carbon from organic sources
Hyphal tips release enzymes
Enzymatic breakdown of substrate
Products diffuse back into hyphae
Enzymatic breakdown
Most enzyme release (and absorption) at tips
Proteins and other materials synthesized by the entire mycelium are channeled by cytoplasmic streaming to the tips of the extending hyphae.
Nucleus hangs back
and “directs”
Products
Enzymes
Product diffuses back
into hypha and is used

6. Fig 31.1
fruiting bodies
both are composed of hyphae
mycelium

7. Modifications of hyphae
Fig 30.2 (don’t worry about the terms)

8. Hyphal growth Hyphae grow from their tips
Mycelium = extensive, feeding web of hyphae
Mycelia are the ecologically active bodies of fungi
This wall is rigid
Only the tip wall is plastic and stretches

9. Reproduce by spores Spores are reproductive cells Formed: Sexual
Asexual
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
Pilobolus sporangia
Amanita fruiting body

10. Hyphal growth from spore
germinating
spore
Fungal mycelia can be huge, but they usually escape notice because they are subterranean.
One giant individual of Armillaria ostoyae in Oregon is 3.4 miles in diameter and covers 2,200 acres of forest,
It is at least 2,400 years old, and weighs hundreds of tons.
(Actually noone has seen this of this extent – but cultures have been taken from soil over that area and all isolates have been found to be the same individual)
Ten cubic centimeters of rich organic soil may have fungal hyphae with a surface area of over 300 cm2
mycelium
Mycelia have a huge surface area (think honey mushroom)

11. Fungal Ecology Saprobes Parasites Mutualists Decomposers
Mostly of plants, some animals
Parasites
Harm host
Mostly on plants, some animals
Mutualists
Lichens
Mycorrhizas
Others
Saprobic fungi absorb nutrients from nonliving organisms.
Parasitic fungi absorb nutrients from the cells of living hosts.
Some parasitic fungi, including some that infect humans and plants, are pathogenic.
Mutualistic fungi also absorb nutrients from a host organism, but they reciprocate with functions that benefit their partner in some way

12. Yeasts Lichens Molds Mycorrhizas A rust growing on a currant leaf
Rusts are Basidiomycote plant parasites with, often, very complex life cycles that alternate between two different plant hosts. They can produce up to 5 different types of spores and cause considerable damage, particularly to economically important plant hosts that are non-natives.
A rust growing on a currant leaf
0.5 cm

13. Yeasts Single celled fungi Adapted to liquids Plant saps Water films
Moist animal tissues
Bread and wine yeast, the budding yeast, Saccharomyces
Easily cultured. For a time, this was the most important organism for studying the molecular genetics of eukaryotes
Thus, Saccharomyces is arguably the most important organism known to humans
Candida causes diseases of humans, usually experiencing chemical imbalance or immune problems
Candida
Saccharomyces

14. Lichens “Mutualism” between Fungus – structure
Alga or cyanobacterium – provides food
Thallus is a plant-like body that doesn’t have roots, stems or leaves
Thallus doesn’t look like either partner
Dual nature of thalli was not fully understood until early 1900’s
Fungus gives the name to the lichen (by agreement)
Fungus usually, but not always, an Ascomycote (in 8+ independent orders)
Algae green. If bluegreen bacteria present, lichens fix nitrogen (turn atmospheric nitrogen into amino acid nitrogen in proteins)
Fig 31.16

15. Lichen internal structure
Fig 31.17
The nature of lichen symbiosis is may also be described as mutual exploitation instead of mutual benefit.
Lichens live in environments where neither fungi nor algae could live alone.
While the fungi do not not grow alone in the wild, some (but not all) lichen algae occur as free-living organisms.
If cultured separately, the fungi do not produce lichen compounds and the algae do not “leak” carbohydrate from their cells.
In some lichens, the fungus invades algal cells with haustoria and kills some of them, but not as fast as the algae replenish its numbers by reproduction.
Lobaria oregana prefers old-growth conifer canopies in forests with clean air.
Lobaria

16. Schizosaccharomyces octospora – fermenter of Palm Wine
This yeast is isolated from palm wine (fermented sap of the oil palm in West Africa)
Note that it is forming 8-spored asci (“octospora”) – an indication that it is an Ascomycote
10 μm

17. Molds Rapid growth Asexual spores Many human importances Food spoilage
Food products
Antibiotics, etc.
A mold is a rapidly growing, asexually reproducing fungus.
The mycelia of these fungi grow as saprobes or parasites on a variety of substrates.
Also used in foods (Blue cheese, Tempeh) and in industrial production of drugs
Early in life, a mold, a term that applies properly only to the asexual stage, produces asexual spores.
Later, the same fungus may reproduce sexually, producing zygosporangia, ascocarps, or basidiocarps
Some molds go through a “fake sex” process
Noble Rot - Botrytis
Fig Antibiotic activity

18. Mycorrhizas “Fungus roots” Mutualism between: Several kinds
Fungus (nutrient & water uptake for plant)
Plant (carbohydrate for fungus)
Several kinds
Zygomycota – hyphae invade root cells
Ascomycota & Basidiomycota – hyphae invade root but don’t penetrate cells
Extremely important ecological role of fungi!
Half of the mushroom-forming fungi (basidiomycota) form mycorrhizas with trees
Some people think that the spongy tissue in roots evolved as a place where fungi could invade to form early links with plants that helped them survive the harsh life on early earth

19. “Ecto”mycorrhizas Russula mushroom mycorrhizas on Western Hemlock root
Mycorrhiza cross sections
4 of the regions where mycorrhizas are found are circled.
These are “ecto” because the hyphae remain outside the root cells (though they extend inside the root)
Fungal hyphae around root and between cells

20. Mushroom Life Cycle Hyphal fusion of haploid mycelia
mycelium and fruiting body are dikaryotic
haploid mycelium
Mushroom Life Cycle
N N N+N
Meiosis
Nuclear fusion in basidium
young basidia - the only diploid cells
Fig 31.12