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Fungi
Ch 14.
General Characteristics
• Eukaryotic
• Nuclear envelope does not break down during mitosis &
meiosis.
• Heterotrophic absorbers
• Primary storage carb is glycogen.
• Chitin in cell walls
walls.
• Grow in filaments called hyphae.
– Large clusters of hyphae = mycelium
• Distinctive fruiting bodies
– Used for identification
• Make spores asexually.
• Zygotic life cycle.
• Symbiotic relationships with plants.
Great diversity
• 70,000 species.
• 1,700 new species
discovered each
year.
• Fungi
F
i 2ndd only
l tto
insects in diversity.
• Armillaria ostoyae
encompasses nearly
900 ha. in Oregon.
– Largest living
organism on Earth?
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Importance of Fungi
• Ecologically important
– Function as decomposers
• Medical & economical importance as:
– Pests,
P t pathogens,
th
& producers
d
off certain
t i
chemicals.
• Form symbiotic relationships
– Mainly in plant roots.
Fungi as decomposers
• Principle decomposers in the biosphere.
• Releases CO2, returns N to soil.
• Top 20cm of fertile soil – 5 metric tons of
f
fungi
i&b
bacteria.
t i
• Attack foodstuffs, decreasing palatability
– Toxic substances known as mycotoxins.
Fungi as pathogens
• Most important causal agent of plant
diseases.
• Most common in tropical regions.
• 40% off hospital
h
it l deaths
d th iin 80’
80’s d
due tto
fungi.
Chytrid
Red Fungus
Rhizopus
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Beneficial fungi
Saccharomyces cerevisiae
Penicillium roquefortii
Conidia of the fungus
(spores)
Fungi as symbionts
• 80% of plants form mutualisms
– Mycorrhizae (between roots & fungi)
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Types of mycorrhizae
• Ectomycorrhizal
– Usually a gymnosperm (pines)
• Endomycorrhizal
E d
hi l
– Usually orchids & ericoids
(rhododendrons)
– Also, citrus, coffee, & rubber
Fungi Phyla
A closer look!!!!!
Four major phyla of fungi
• Chytridiomycota
– Chytrids
• Zygomycota
– Zygomycetes
• Ascomycota
– Ascomycetes
• Basidiomycota
– Classes Basidiomycetes, Teliomycetes, &
Ustomycetes
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Major Characteristics of Fungal Phyla
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Hyphae
• Hyphae – fungal filaments
• Mycelium – mass of hyphae
– Individual fungus may produce > 1 km of new
hyphae within 24 hrs.
hrs
• Septa – divide hyphae (crosswalls)
• Such hyphae are called ‘septate’.
• Hyphae lacking septa are called ‘aseptate
or coenocytic’.
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Heterotrophic absorbers
• Absorb b/c cell walls are rigid.
• Occurs near growing tips of hyphae.
• Function as:
– Saprophytes (living on organic materials)
have rhizoids.
– Parasites - haustoria
– Mutualists
Mitosis & Meiosis
• Nuclear envelope does not disintegrate &
re-form.
• Form spindle pole bodies
– SPB’s
SPB’ and
d centrioles
t i l ffunction
ti as microtubule
i t b l
organizing centers during mitosis & meiosis.
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Reproduction
• Both sexual & asexual
• Asexual
– Spores
• Spo
Sporangia
a ga o
or co
conidiogenous
d oge ous ce
cells
s
• Sexual
– 3 phases
• Plasmogamy (fusion of protoplasts)
• Karyogamy (fusion of nuclei)
• Meiosis
The Chytrids: Chytridiomycota
• Predominantly aquatic
(790 spp.)
• Chitin
• Store glycogen
• Coenocytic
• Motile cells (zoospores &
gametes)
• Infect a number of hosts
Batrachochytrium dendrobatidis
(Bd)
© Forrest Brem
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Allomyces arbusculus –Alteration of isomorphic generations
Bd life cycle
Zygomycetes: Zygomycota
• Mostly parasites & mutualist (~ 1060 spp.)
• Coenocytic hyphae
• Usually have profuse, rapidly growing
h h
hyphae:
– Hyphae called ‘stolons’ form rhizoids
• Named for sexually produced
‘zygospores’.
• Form endomycorrhizal associations
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Rhizopus stolonifer
Gametangia – fusing to
produce zygospore
Zygospore developing
within zygosporangium
Ascomycetes: Ascomycota
• Blue-green, red, and brown molds (~32,00
spp.)
• Unicellular or filamentous growth
p of modified hyphae
yp
• Conidia borne at tips
called “conidiophores”.
• Asexual spores are produced externally as
conidia.
• Sexual reproduction involves the formation of
an ascus which ascospores are produced.
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Two asci
Ascoma
Ascoma
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• Asci develop on inner surface of ascoma
called hymenium.
• Antheridia “male gametangia”
• Ascogonia “female gametangia”
Basidiomycetes, Teliomycetes, &
Ustomycetes: Basidiomycota
• Most familiar fungi (~ 22,000 spp.)
• Mushrooms, toadstools, puffballs, shelf
fungi.
• Produce
P d
b idi
basidiospores
b
borne
outside
t id clubl b
shaped basidium.
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Class Basidiomycetes
• Includes Hymenomycetes & Gasteromycetes.
• Edible & poisonous mushrooms, coral fungi,
tooth fungi, and shelf & bracket fungi.
• Referred
R f
d as hymenomycetes
h
t because
b
basidiospores are produced on the hymenium.
• Gasteromycetes have no distinct hymenium is
visible.
– False puffballs, bird’s nest fungi, and puffballs.
Hymenomycetes
• Toadstools usually
recognized
– Pileus (cap)
– Stipe (stalk)
– Gills
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Mycelium spreads and dies in center
Gasteromycetes
• Form peridium (outer covering)
– Opens naturally, spores not expelled
• Some cases spores need to be liberated by
g etc…))
external source ((i.e., animal or tree falling
Puffballs
Netted Stinkhorn
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Teliomycetes
• Referred to as rusts
– Billions of dollars in
crop damage
• Heteroecious
– Two hosts to
complete life cycle
• Autoecious
– One host
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Ustomycetes
• Parasites to
flowering plants
– a.k.a smuts
• Autoecious
Yeasts
• Unicellular fungus
• Saccharomyces
cerevisiae
Conidial Fungi
• a.k.a Anamorphs
• Medically important
– Penicillium (penicillin-producing fungi)
– Aspergillus
A
ill (respiratory
(
i t
di
diseases))
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Symbiotic relationships
• Mutualisms or parasitisms
• Lichens
– Mycobiont + Photobiont
• 98% b
belong
l
tto A
Ascomycota
t
• Remaining belong to Basidiomycota
Mycorrhizae
• “Fungus roots”
• Endomycorrhizae
– Penetrate root cells
– Often
Oft called
ll d “V
“Vesicular-arbuscular”
i l
b
l ”
mycorrhizae
• Ectomycorrhizae
– Surround root cells
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Endomycorrhizae
Ectomycorrhizae
Summary
•
•
•
•
•
•
•
•
•
•
•
•
•
Ecologically & Economically important
Most composed of hyphae
Absorb & produce spores
4 distinct phyla
Chytrids form flagellated, motile cells.
Zygomycota form zygospores in zygosporangia.
zygosporangia
Ascomycota form ascospores internally in asci.
Basidiomycota form basidiospores externally on basidia.
Mushrooms, rusts, & smuts represent 3 classes of Basidiomycota.
Yeasts are unicellular.
Fungi with no sexual state are Conidial Fungi.
Lichens = Mycobionts + Photobionts
Mycorrhizae = mutualistic associations between Fungi & Roots.
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