Download fungi are heterotrophs mycelia can be huge!!

Bio153S: lecture 12
biology of fungi (I)
Ch. 31 in text
(* phylogeny in text is not the same as
presented here)
today’s lecture = end of material for
midterm
fungi are heterotrophs
• “osmotrophs”: digest, then ingest
• hydrolytic exoenzymes
• can break down lignin, cellulose
(also petroleum, waxes,
photographic film…)
• saprobes, parasites, predators,
mutualistic symbionts…
fungi used to be considered
plants
• thought to be primitive plants
lacking chlorophyll
• now thought to be phylogenetically
closer to animals
• monophyletic group > 600 my old
• ~ 100,000 described spp.
• may be 1.5 million spp.
• 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:
• 860ha
• 2,600 years old!
Armillaria ostoyae
1
• 1 cm3 of soil : 1 km of hyphae;
surface area > 300 cm2
structure of hyphae:
• mycelia are nonmotile; grow rapidly
• ↑ hyphal length rather girth;
maximize SA : vol
modified hyphae:
predacious fungi:
• haustorium: modified hypha for
penetration
origins:
• evolved from unicellular,
aquatic, flagellated
ancestor
• member of clade
Opisthokonta (includes
animals & some protists)
• adaptive radiation:
colonized land
~ 460 m.y. old fossil
paraphyletic?
2
Chytridiomycota:
• flagella may
have been
lost more
than once
• 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
3
Ascomycota
Ascomycota
• some secondarily unicellular (derived)
e.g. Saccharomyces
powdery mildew
black spot
• reproductive structure = ascus
Geopora
cup fungus
~40% of Ascomycota:
symbiosis with algae, cyanobacteria
- LICHENS
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)
Geastrum
Lycoperdon
Basidiomycota
Auricularia
Phallus
Tremella
4
Basidiomycota
Phlogiotis
Amanita
• “fairy ring”: outward growth of
mycelium; appearance of fruiting
bodies
Ganoderma
Saprobes
Saprobes
• dead organic material - scavengers
• decomposers, cycling C, N etc.
(as do bacteria)
• abundant in soils
• intimate association with roots
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
• virtually all animals & plants
are susceptible
• plant pathogens;
blights, mildews, rusts
• plants can evolve resistance;
fungi respond by castrating hosts
Parasites
• parasite affects host behaviour
and physiology
• direct impact of
secreted chemicals
on
nervous system
• ergot of rye;
Salem witches
5
FungusFungus-garden ants:
• ants feed and tend
fungus
in special chambers
• fungal hyphae are
sole food of larvae
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
next: life-cycles of fungi
6