FUNGI
Chapter 31
The Little Known Fungi
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100,000 species known, 1.5 million unknown (estimate)
Some are single-celled (yeast), but most multicelled
(mushrooms)
Found in every habitat
Diverse, widespread, and essential for well-being
Formerly classified as plants
 Molecular
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data says more closely related to animals
Mycologists are the scientists that study fungi
Nutrition
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Heterotrophs, but absorb food instead of digest
 Secrete
enzymes into environment to break complex
molecules into something more manageable
 Enzymes also disrupt walls of plant cells for nourishment
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Live as decomposers, parasites, or mutualisms'
 Fit
into multiple niches
 Can digest wide range of food sources
Body Structure
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Most grow as filaments and
yeasts
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Yeast only growth is rare
Bodies form filamentous
networks called hyphae
Form a mycelium to increase
SA/volume ratio
 Proteins synthesized to
rapidly extend (not grow)
hyphae
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Concentratie of energy and
resources to accomplish
Not motile, but can move
hyphae
Specialized Hyphae
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Some allow predation of
living animals
Haustoria allow nutrient
extraction or exchange
Mycorrhizae are mutually
beneficial relationships
between fungi and plants
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Improve mineral delivery to
plants in exchange for carbs
Ectomycorrhizal fungi: form a
sheath of hyphae over plant
roots and between plant cells
Arbuscular mycorrhizal
fungi: extend hyphae through
root cell walls and into plant
Sexual Reproduction
Hyphae release
pheromones
Different mating types
attract
Heterokaryon, nuclei
don’t fuse right away
Dikaryotic, nuclei pair off
and divide without fusing
Time to karyogamy varies
Usually only 2n stage
Final steps generate
genetic variation
Asexual Reproduction
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Varies widely among fungi
(like sexual)
Produce haploid spores by
mitosis
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Informally known as molds if
mycelia is visible
Grow rapidly and
reproduce sexually if
contacted by species of
different mating type
Yeasts produce budding
cells or spores via mitosis
Deuteromycetes reproduce
asexually only
5 phyla recognized
currently, but chytrids
are likely paraphyletic
Study cycle diagrams
for reproductive
differences
Fungi Functional Groups
Chytridium globular fruiting bodies,
one of the earliest to diverge
Mucor, grow into fruits and breads;
may act as decomposers, parasites,
or symbionts
Ecologically important; form
mycorrhizal associations with
plants
Sac fungi, common to
water and land Aleuria
aurantia
Decomposers and
ectomycorrhizal fungi;
fruiting bodies commonly
called mushrooms
Phylum Chytridiomycota
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Called chytrids and found in
lakes and soil
Decomposers and pararsites of
protists, other fungi, plants, or
animals
 Live
in sheep GI tracts to help
process plants
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Some form colonies with
hyphae, others as single cells
Only phyla with flagellated
spores called zoospores
Phylum Zygomycetes
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Reproduce by zygospores
Sexually, formed in
zygosporagium
 Asexually, formed atop
sporangiophores
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Rhizopus stolonifer is black
bread mold
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Know the life cycle
Philobolus ‘aim’ and shoot
sporangium
Resistant to freezing and
drying
Phylum Glomeromycetes
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Form arbuscular
mycorrhizae
 Tips
of hyphae push
into plant root cells
and branch into
treelike structures
 Minerals to plant and
organic compounds to
fungi
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Mutualistic partnership
with 90% of all plant
species
Phylum Ascomycetes
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Reproduce sexually by spores in asci (sacs) and
bear stages in ascocarps (fruiting bodies)
Reproduce asexually by conidiospores, spores
formed at tips of hyphae called conidiophores
Include: morels and truffles
Yeasts used in beer industry
Phylum Basidiomycetes
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Includes mutualists that form
mycorrhizae and plant
parasites
Reproduce sexually by
producing fruiting bodies
called basidiocarps
 Produces
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4 haploid nuclei
Asexual reproduction is
rare
Fungal Phylum Review
Decomposers
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Any carbon containing substance can be consumed
by some fungi
Important use in bioremediation
Maintain essential inorganic nutrients for plant
growth
Return nutrients to the soil
Mutualists
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Fungus-Plant
 Ascomycetes
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benefit by producing toxins to deter prey
Fungus-Animal
 Decomposers
convert otherwise indigestible plant
material
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Lichens: symbiotic association with algae
 Algae
contribute carbon compounds and fix nitrogen
 Fungi contribute suitable environments for growth
 Reproduce separately
 Lichen:
asexually via soredia, clusters of hyphae with algae
Pathogens
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Mostly on or in plants
 Ascomycete
Cryphonectria parasitica attacks chestnuts
 Basidiomycete Puccinia graminis causes black stem rust
on wheat
 Ascomycete Aspergillus contaminates improperly stored
grains and peanuts by secreting carcinogenic aflatoxins
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Mycosis are those that parasitize humans
 Ascomycetes
cause ringworm and athlete’s foot
 Coccidioidomycosis produces tuberculosis like symptoms
in lungs
 Candida albicans normal on moist epithelia, grow to
rapidly causes vaginal infections, diaper rash, and thrush
Practical Uses
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Food
Flavors of cheese
 Aspergillus used for citric acid
in cola
 Yeasts for breads, beer, and
wine
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Medicine
Antibiotic treatments
 Penicillium used to produce
penicillin
 Saccharomyces used to study
Parkinson’s and Huntington’s
disease
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