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Fungi
Learning Objectives
• By the end of this unit, a student should be able to…
• List distinguishing characteristics, describe a typical life cycle,
and give examples of each of the following fungal groups:
chytridiomycetes, zygomycetes, glomeromycetes, ascomycetes,
and basidiomycetes
• Describe the body plan of a fungus
• Summarize the ecological significance of fungi as decomposers
• Describe the important ecological role of mycorrhizae
• Characterize the unique nature of a lichen
• Summarize some specific ways that fungi affect humans
economically
• Summarize the importance of fungal diseases to agriculture and
medicine; giving specific examples
Distinguishing characteristics of Fungi
• Eukaryotic heterotrophs
• Secrete digestive enzymes externally, absorb nutrients
• Cell walls contain chitin
• fibrous polysaccharide
• polymer of a N-acetylglucosamine (derivative of glucose)
• also found in exoskeleton of arthropods
Fungal Structure
• Threadlike filaments (hyphae)
• Branch and form a tangled mass (mycelium)
Fungal Structure
• Threadlike filaments (hyphae)
• Branch and form a tangled mass (mycelium)
Fungal Structure
• Hyphae
• Perforated septa
(cross walls) divide
hyphae into individual
cells
• Some are coenocytic
• form elongated,
multinuclear cell
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Fungal Reproduction
• reproduce with Spores
• sexual
• asexual
• produced on aerial hyphae
• produced in a “fruiting
body”
Fungal Reproduction
Giant Puffball (Calvatia gigantea)
• A single ten-inch giant puffball has as many as
7 trillion (7,000,000,000,000) spores.
• If each of those spores grew and yielded a ten-inch
puffball, the combined mass would be 800 times that
of the earth.
• From the Cornell Mushroom Blog, David Landers
Yeast
• Yeasts are a type of single celled fungus
• highly reduced mycelium
• reproduce asexually by budding
Life cycles
• Mitosis
• Meiosis
• Fertilization
Ex: Homo sapiens
Fungal Life cycles
Fungal Life Cycle
n
haploid mycelium
dikaryotic
mycelium
Spores n
n
mitosis
meiosis
n
plasmogamy
n + n
karyogamy
2n
diploid
mycelium
n n
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haploid mycelium
dikaryotic
mycelium
Spores
mitosis
meiosis
plasmogamy
karyogamy
diploid
mycelium
(n)
Fungal Life cycles
asexual cycle of
haploid mycelium
Spores (n)
Fungal Evolution
• Chytridiomycetes
• Zygomycetes
• Glomeromycetes
• Ascomycetes
• Basidiomycetes
Chytrids (Chytridiomycetes)
• Produce flagellate cells
• no other fungi have flagella
• a shared characteristic of the
opisthokonts
• Probably earliest fungi to
evolve from flagellate protist
Chytridium convervae
Chytrids (Chytridiomycetes)
• “Chytrid” and Chytridiomycosis disease
• Massive amphibian die-off
• mainly in tropics
• Caused by fungus Batrachochytrium dendrobatidis
Chytrids (Chytridiomycetes)
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Fungal Evolution
• Chytridiomycetes
• Zygomycetes
• Glomeromycetes
• Ascomycetes
• Basidiomycetes
Zygomycota
• Hyphae are coenocytic
• septa form to separate the hyphae from
reproductive structures
Zygomycota
• Sexual reproduction
• hyphae of 2 different mating types form gametangia
• Plasmogamy occurs as gametangia fuse
• Karyogamy produces zygote (2n)
• zygote develops into zygosporangium
Zygomycota
• Sexual reproduction
• zygosporangium produces zygospores (n)
• zygospores germinate and produce sporangia
• sporangia produce spores (n) which germinate into new
hyphae
Zygomycota Life Cycle
Example:
Rhizopus stolionifer
(black bread mold)
Zygomycota
• Microsporidia
• Small, unicellular opportunistic pathogens that infect
eukaryotic cells
• May be the smallest and simplest eukaryotes
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Zygomycota
• Microsporidia
• Previously classified with yeasts, bacteria, and protista
• Genome studies suggest that microsporidia descended
from a zygomycete ancestor
Fungal Evolution
• Chytridiomycetes
• Zygomycetes
• Glomeromycetes
• Ascomycetes
• Basidiomycetes
Glomeromycetes (Phylum Glomeromycota)
• Coenocytic hyphae
• reproduce asexually with large, multinucleate
blastospores
• form mycorrhizae
• mutualistic symbiosis with plant roots
Glomeromycetes (Phylum Glomeromycota)
• Mycorrhizae*
• form associations with roots of
trees and herbaceous plants
• specifically, endomycorrhizal
• grow into plant root cells
• called arbuscular
mycorrhizae
• form tree-shaped
structures
* a description of ecology, not phylogeny
–Johnny Appleseed
“Type a quote here.”
Cells of root
cortex Root epidermis
Soil Vesicle
Root hair
Arbuscule Spore
Cortex cell
Hypha of fungus
Mycorrhizal Associations
• Roots supply organic nutrients
• Fungus provides mineral nutrients
Pine w/o mycorrhizae Pine with mycorrhizae
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Fungal Evolution
• Chytridiomycetes
• Zygomycetes
• Glomeromycetes
• Ascomycetes
• Basidiomycetes
Ascomycetes (Phylum Ascomycota)
• Ascomycetes include
• yeasts
• cup fungi
• morels
• truffles
• pink, brown, and blue-
green molds
Ascomycetes
• Have septate hyphae
• Produce coenocytic sexual hyphae
• Following plasmogamy, dikaryotic (n + n) hyphae
form in an ascocarp* (fruiting body)
Ascocarp -
“fruiting body”
*made of monokaryotic hyphae
Ascomycetes
• Karyogamy occurs at tips of hyphae (asci)
• followed by meiosis and mitosis
• produces 8 haploid nuclei that develop into ascospores
Asci - form
sexual spores in
groups of 8
Ascomycetes (Phylum Ascomycota)
• Asexual reproduction
• involves formation of
colored spores (conidia)
at the tips of specialized
hyphae (conidiophores)
Penicillium conidiophores
–Johnny Appleseed
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Fungal Evolution
• Chytridiomycetes
• Zygomycetes
• Glomeromycetes
• Ascomycetes
• Basidiomycetes
Basidiomycetes
• Phylum Basidiomycota
• include the largest and
most familiar of the fungi
• mushrooms
• bracket fungi
• puffballs
• rusts
• smuts
Basidiomycetes
• Septate hyphae
• a secondary mycelium
forms after plasmogamy
• dikaryotic hyphae
• compact buttons grow into
mushrooms (fruiting bodies)
called basidiocarps
Basidiomycetes (Phylum Basidiomycota)
• Karyogamy takes place within
young basidia on the gills of the
mushroom
• each basidium produces 4
basidiospores
–Johnny Appleseed
“Type a quote here.”
Basidiospores
released
Plasmogamy
HAPLOID (n)
STAGE
Second meiotic
division DIKARYOTIC
STAGE
(n + n) First meiotic
division DIPLOID (2n)
STAGE
Meiosis Zygote
Karyogamy Gills Basidiocarp
Secondary mycelium
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2
3
4
5
6
7 • Many basidiomycetes produce “fairy rings” in lawns
and forests
• The circle widens as the fungi grow outward
Basidiomycetes