Biological Science 2/e

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Transcript Biological Science 2/e

A fungus is not a plant.
Multicellular fungi consist of mycelium,
which are made up of strands called hyphae.
Hyphae have enormous surface areas.
Absorbs food from environment.
Prone to drying out.
Most of “body” of fungus is feeding structure.
Only reproductive body typically exposed to air.
Thick, fleshy structure of “shroom” prevents drying out.
Reproductive structure produces spores
Ascomycetes have
spores in sacs.
Basidiomycetes have
spores on clubs.
In fungi, cytoplasm of two individuals fuses, but
their nuclei may remain separate for a long time.
Fungal phylogeny is a work in progress!
No point in learning this now, will change.
Importance of Fungi:
1. Decomposers
2. Mycorrhizae
3. Lichens
4. Economic Impacts
Fungi as decomposers
Basidiomycete fungi are the only organisms
that can completely digest the lignin in wood.
Fungi serve an essential role in the carbon cycle.
Adaptations helping with decomposition:
1. Extracellular digestion
Only small molecules can cross plasma membranes.
Secreted enzymes break down large molecules.
Adaptations helping with decomposition:
2. Lignin peroxidase
Enzyme catalyzes removal
of a single electron; creating a
highly reactive atom.
“Enzymatic combustion”
Uncontrolled oxidation reaction
breaks up polymer.
(Most enzymatic reactions very
specific, but lignin itself highly
Randomness of reaction means
that E from oxidation can’t be
Adaptations helping with decomposition:
3. Cellulose digestion
By cutting up lignin, fungi
gain access to cellulose.
The cellulase enzymes
digest cellulose into
glucose, which can be
used for food.
Importance of Fungi:
1. Decomposers
2. Mycorrhizae
3. Lichens
4. Economic Impacts
Fungi as partners with plants: Mycorrhizae
Importance of mycorrhizae discovered in ‘70’s.
Failure of pine plantations key observation.
Fungi as partners with plants: Mycorrhizae
EM fungi on most trees in temperate & boreal forests.
Hyphae penetrate dead leaves, twigs.
Release enzymes that cleave peptide bonds.
Provide N to plant in exchange for C.
Fungi as partners with plants: Mycorrhizae
AMF important in tropics and grasslands, on 80% of plants.
Ancient; fossil from 400 mya.
Provide phosphorus to plant in exchange for C.
Importance of Fungi:
1. Decomposers
2. Mycorrhizae
3. Lichens
4. Economic Impacts
Fungi as colonizers: lichens
Lichens are composed of fungal
hyphae and a layer of autotrophic
green algae or cyanobacteria
Colonize bare rock following
First stage in soil building.
Importance of Fungi:
1. Decomposers
2. Mycorrhizae
3. Lichens
4. Economic Impacts
Of course, the most important economic
impacts are those already mentioned.
Fungi rot crops.
A fungus called ergot is associated with
accusations of witchcraft.
Ergot poisoning causes convulsions, shaking, or spasms
and sometimes hallucinations or gangrene.
Ergot is the original source from which LSD first isolated.
Fungi are thought to contribute to the worldwide
decline of amphibian populations.
A fungus has caused the
virtual extinction of
the American chestnut.
Note the man, to show
The first antibiotic was derived from Penicillium.
This is also the genus used to make blue cheeses.
Penicillium roquefortii is used in the manufacture of blue cheeses e.g. Roquefort, Gorgonzola, Stilton, etc.
During the fermentation process the fungus spores are injected into the curd.
By the way, the blue in the blue-cheese is caused by the pigment in the spores of the fungus.
So, when you eat blue cheese you are consuming spores by the million.
Yeast is the
of eukaryote
Yeasts are also essential
to the production
of wine, beer and bread.
Some fungi are just really cool.