Download fungi are heterotrophs mycelia can be huge!!

Summer Bio153S: lecture 9
biology of fungi (I)
• fungi used to be considered primitive
plants
• now thought to be phylogenetically
closer to animals
• monophyletic group > 600 my old
• ~ 100,000 described spp.
• may be 1.5 million spp.
fungi are heterotrophs
• “osmotrophs”: digest, then ingest
• hydrolytic exoenzymes
• can break down lignin, cellulose
(also petroleum, waxes,
photographic film…)
• saprobes, parasites, predators,
mutualistic symbionts…
• some exist as single cells (yeasts)
• most multicellular
• body = mass of hyphae
• cell walls contain chitin (N–rich
polysaccharide)
mycelia can be huge!!
• a honey fungus in
Oregon:
• 860 ha
• 2,600 years old!
Armillaria ostoyae
• 1 cm3 of soil : 1 km of hyphae;
surface area > 300 cm2
• mycelia are nonmotile; grow rapidly
• ↑ hyphal length rather girth;
maximize SA : Vol
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structure of hyphae:
modified hyphae:
• haustorium: modified hypha for
penetration
predaceous fungi:
origins:
• evolved from unicellular,
aquatic, flagellated
ancestor
• member of clade
Opisthokonta (includes
animals & some protists)
• adaptive radiation:
colonized land
~ 460 m.y. old fossil
• flagella may
have been
lost more
than once
paraphyletic?
2
Chytridiomycota:
• ancestral form
• mostly freshwater; some are
commensals in guts of mammals
(anaerobic)
• saprobes and parasites
Zygomycota:
• 1,000 species
• molds etc.
• some single cells
• unique: motile spores (zoospores)
other Zygomycota:
• Microsporidia: unicellular parasites
• affect people with HIV
recently classified in
Zygomycota
Rhizopus
(bread mold)
Glomeromycetes:
• formerly in Zygomycota
• all form mycorrhizae (symbiotic
associations with roots of plants
• 90% of plant species
Ascomycota
• some secondarily unicellular (derived)
e.g. Saccharomyces
• reproductive structure = ascus
Geopora
cup fungus
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Ascomycota
powdery mildew
black spot
~40% of Ascomycota:
symbiosis with algae, cyanobacteria
- LICHENS
• diverse, probably evolved from
parasitism
• extremely resistant, except to SO2
• prominent in Arctic; soil formation
Basidiomycota
• most “mushrooms” and bracket fungi
• important decomposers
• some pathogens (rusts & smuts)
lichens:
Geastrum
Lycoperdon
Basidiomycota
Basidiomycota
Auricularia
Phlogiotis
Amanita
Phallus
Tremella
Ganoderma
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Saprobes
• dead organic material - scavengers
• decomposers, cycling C, N etc.
(as do bacteria)
• “fairy ring”: outward growth of
mycelium; appearance of fruiting
bodies
Saprobes
in direct competition with bacteria;
some bacteria prey on fungi
fungi respond: secreted metabolites ⇒
kill or inhibit bacterial growth
• antibiotics & bacteriostats
• suppress immune system e.g. cyclosporin
Parasites
• parasite affects host behaviour
and physiology
• direct impact of
secreted chemicals
on
nervous system
• ergot of rye;
Salem witches
• abundant in soils
• intimate association with roots
Parasites
• virtually all animals & plants
are susceptible
• plant pathogens;
blights, mildews, rusts
• plants can evolve resistance;
fungi respond by castrating hosts
FungusFungus-garden ants:
• ants feed and tend
fungus
in special chambers
• fungal hyphae are
sole food of larvae
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FUNGI & HUMANS
HARM
rot, decay of foods and goods;
direct poisons
disease of humans; domestic organisms
HELP
edible fungi;
cheese manufacture
Saccharomyces cerevisiae
yeast -> bread, wine, beer, whiskey
Aspergillus - soy sauce
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