Kingdom Fungi
Chapter 26
Learning Objective 1
•
What are the distinguishing characteristics
of kingdom Fungi?
Fungi
•
Eukaryotic heterotrophs
•
Secrete digestive enzymes onto food
•
•
then absorb predigested food
Cell walls with chitin
KEY CONCEPTS
•
Fungi are eukaryotic heterotrophs that
absorb nutrients from their surroundings
Learning Objective 2
•
What is the body plan of a fungus?
Fungi Structures
•
Fungi include
•
•
•
unicellular yeast
filamentous, multicellular mold
Most multicellular fungi
•
•
have long, threadlike filaments (hyphae)
branch and form a tangled mass (mycelium)
Insert “Mycelium”
mycelium.swf
Learn more about mycelium by
clicking on the figure in
ThomsonNOW.
Hyphae
•
In most fungi
•
•
perforated septa (cross walls) divide hyphae
into individual cells
In some fungi
•
•
zygomycetes and glomeromycetes
hyphae are coenocytic (form elongated,
multinuclear cell)
Fungus Body Plan
Hyphae
25 µm
Fig. 26-1 (a-b), p. 557
Fig. 26-1 (c-e), p. 557
KEY CONCEPTS
•
A fungus may be a unicellular yeast or a
filamentous, multicellular mold consisting
of long, branched hyphae that form a
mycelium
Learning Objective 3
•
What is the life cycle of a typical fungus,
including sexual and asexual
reproduction?
Reproduction
•
Most fungi reproduce sexually and
asexually by spores
•
Spores
•
•
produced on aerial hyphae
land in suitable spot and germinate
Germination of a Spore
Spore
Hypha
Mycelium
Fig. 26-2, p. 557
Asexual Reproduction
Bud development
Fig. 26-3a, p. 558
Fig. 26-3b, p. 558
Plasmogamy
•
Fungi of two different mating types meet,
hyphae fuse
•
•
•
cytoplasm fuses
nuclei remain separate
Fungi enter dikaryotic (n + n) stage
•
each new cell has one nucleus of each type
Karyogamy
•
Fusion of nuclei
•
•
takes place in hyphal tip
results in diploid (2n) zygote nucleus
Genetic Divisions
•
Meiosis
•
•
•
produces 4 different haploid (n) nuclei
each nucleus becomes part of a spore
Mitosis
•
forms new mycelia when spores germinate
Asexual Spores
•
Can be produced by mitosis
•
•
genetically similar
When these spores germinate
•
they also develop into mycelia
Fungal Life Cycles
7
Large numbers of
haploid (n) spores are
produced by mitosis.
Spores germinate 1
and form mycelia
by mitosis.
6
Spores are
released.
5
Meiosis results in
four genetically
different haploid ( n )
nuclei. Spores
develop around
nuclei.
Spores
Asexual
reproduction
Mycelia
8 Spore germinates
and forms mycelium
by mitosis.
Mycelia of two different
mating types fuse at their
2 tips, and plasmogamy
(fusion of cytoplasm)
occurs.
Sexual
reproduction
Haploid stage
(n)
Dikaryotic stage
(n + n)
Diploid
stage (2n)
Zygote nucleus
(2n)
Plasmogamy
3 Dikaryotic (n + n)
mycelium develops.
Dikaryotic mycelium
Meiosis
Karyogamy
4 Karyogamy (fusion of nuclei)
occurs, forming a diploid (2 n )
zygote nucleus.
Fig. 26-4, p. 559
KEY CONCEPTS
•
Most fungi reproduce both asexually and
sexually by means of spores
Learning Objective 4
•
Support the hypothesis that fungi are
opisthokonts, more closely related to
animals than to plants
Flagellate Cells
•
Animals and fungi have flagellate cells
•
•
Example: chytrid gametes and spores
Flagellate cells propel themselves
•
with single posterior flagellum
Platelike Cristae
•
Like animal cells, fungal cells have
platelike cristae in their mitochondria
Opisthokonts
•
Fungi are opisthokonts
•
•
along with animals and choanoflagellates
based on chemical and structural characters
Fungal Evolution
Basidiomycetes
Ascomycetes
Zygomycetes
Chytrids
Glomeromycetes
Evolution of
ascospores
Evolution of
basidiospores
Evolution of
dikaryotic stage
Loss of flagellum
Common
flagellate
ancestor
Fig. 26-5, p. 560
Learning Objective 5
•
Support the hypothesis that chytrids may
have been the earliest fungal group to
evolve from the most recent common
ancestor of fungi
Chytrids (Chytridiomycetes)
•
Produce flagellate cells during life cycle
•
•
no other fungi have flagella
Probably earliest fungi to evolve from
flagellate protist
•
common ancestor of all fungi
Chytrid
5 µm
Fig. 26-6, p. 561
Learning Objective 6
•
List distinguishing characteristics, describe
a typical life cycle, and give examples of
each of these fungal groups:
•
•
•
•
•
chytridiomycetes
zygomycetes
glomeromycetes
ascomycetes
basidiomycetes
Chytrids 1
•
Reproduce both asexually and sexually
•
Gametes and zoospores are flagellate
•
Allomyces
•
•
part of life is multicellular haploid thallus
part is multicellular diploid thallus
Chytrids 2
•
Haploid thallus produces 2 types of
flagellate gametes that fuse
•
Both plasmogamy and karyogamy occur
•
producing flagellate zygote
Chytrids 3
•
Diploid thallus bears zoosporangia
•
•
•
produce diploid zoospores, resting sporangia
in which haploid zoospores form by meiosis
Haploid zoospores form new haploid thalli
Chytrid
Life Cycle
Common
flagellate
ancestor
Fig. 26-7a, p. 562
Basidiomycetes
Ascomycetes
Glomeromycetes
Zygomycetes
Chytrids
Mature haploid thallus
Sporangium
1
Haploid
Haploid zoospore zoospore
grows into haploid
thallus.
Haploid thallus
produces two
2 types of gametes
by mitosis.
Gamete
type A
Gamete
type B
SEXUAL REPRODUCTION
6
Haploid
zoospores are
produced by
meiosis.
HAPLOID (n)
Resting
sporangium GENERATION
Meiosis
5
Meiosis occurs in
resting sporangia.
DIPLOID (2n)
GENERATION
Resting
sporangium
Gametes fuse and their
nuclei fuse, producing
3 flagellate zygote.
Plasmogamy
and karyogamy
Motile zygote
Zoosporangium
4 Zygote germinates
and develops into
diploid thallus.
ASEXUAL
REPRODUCTION
(by mitosis)
Diploid zoospore
Zoosporangia produce
7 flagellate diploid
zoospores by mitosis.
Zoospores give rise to
new diploid thalli.
Fig. 26-7b, p. 562
Zygomycetes 1
•
Rhizopus (black bread mold)
•
•
•
forms haploid thallus
produces asexual spores and sexual spores
Asexual spores germinate
•
form new thalli
Zygomycetes 2
•
In sexual reproduction
•
•
hyphae of 2 different haploid mating types
form gametangia
Plasmogamy occurs
•
as gametangia fuse
Zygomycetes 3
•
Karyogamy occurs
•
•
•
diploid zygote forms
from which zygospore develops
Meiosis
•
produces recombinant haploid zygospores
Zygomycetes 4
•
When zygospores germinate
•
•
each hypha develops a sporangium at its tip
Spores are released
•
develop into new hyphae
Zygomycete
Life Cycle
Common
flagellate
ancestor
Fig. 26-9a, p. 564
Basidiomycetes
Ascomycetes
Glomeromycetes
Zygomycetes
Chytrids
Fig. 26-9b, p. 564
Insert “Zygomycete life
cycle”
rhizopus_life_cycle.swf
Microsporidia
•
Microsporidia (now zygomycetes)
•
•
are opportunistic pathogens
penetrate and infect animal cells with long,
threadlike polar tubes
Infection by Microsporidium
Microsporidian cell
Polar tube
Host cell
1
Spore of
microsporidium
has coiled
polar tube.
2
Spore ejects
its polar tube
and penetrates
host cell.
3
Infective
cytoplasm is
injected into
host cell.
Fig. 26-10, p. 565
Microsporidian cell
Polar tube
Host cell
1. Spore of
microsporidium
has coiled
polar tube.
2. Spore ejects
its polar tube
and penetrates
host cell.
3. Infective
cytoplasm is
injected into
host cell.
Stepped Art
Fig. 26-10, p. 565
Glomeromycetes 1
•
Phylum Glomeromycota
•
•
symbionts that form intracellular associations
(mycorrhizae) with plant roots
Endomycorrhizal fungi
•
extend hyphae into root cells
Glomeromycetes 2
•
Arbuscular mycorrhizae
•
•
•
most common endomycorrhizae
hyphae inside root cells form branched, treeshaped structures (arbuscules)
Glomeromycetes
•
•
have coenocytic hyphae
reproduce asexually with large, multinucleate
spores (blastospores)
Arbuscular Mycorrhizae
Cells of
root cortex
Root epidermis
Soil
Vesicle
Root hair
Arbuscule
Spore
Cortex
cell
Hyphae of fungus
Fig. 26-11, p. 565
Ascomycetes 1
•
Produce asexual spores (conidia)
•
Produce sexual spores (ascospores) in
asci
•
Asci line a fruiting body (ascocarp)
•
Conidia
•
Ascocarp
•
Asci
Ascomycetes 2
•
Haploid mycelia of opposite mating types
produce septate hyphae
•
Plasmogamy occurs, nuclei exchanged
•
Dikaryotic n + n stage occurs
•
hyphae form, produce asci and ascocarp
Ascomycetes 3
•
Karyogamy occurs
•
•
Recombinant nuclei divide by mitosis
•
•
followed by meiosis
produce 8 haploid nuclei that develop into
ascospores
When ascospores germinate
•
can form new mycelia
Ascomycetes 4
•
Ascomycetes include
•
•
•
•
•
•
yeasts
cup fungi
morels
truffles
pink, brown, and blue-green molds
Some ascomycetes form mycorrhizae
•
others form lichens
Ascomycete
Life Cycle
Common
flagellate
ancestor
Fig. 26-13a, p. 567
Basidiomycetes
Ascomycetes
Glomeromycetes
Zygomycetes
Chytrids
Conidia
In asexual reproduction,10
hyphae produce haploid
conidia that can develop
into new mycelia.
Haploid
(n)
Conidiophore
When released, 9
ascospores
germinate and
form new
haploid mycelia.
8
Each nucleus
becomes
incorporated
into an
ascospore.
Mature ascus has
eight haploid
ascospores
Second meiotic
division
Germinating
conidium
ASEXUAL
REPRODUCTION
(by conidia)
Haploid mycelia of
1 opposite mating types
both produce coenocytic
sexual hyphae.
(+) mating
type
(–) mating
type
2
Plasmogamy occurs as
hyphae of the two mating
SEXUAL
types fuse and nuclei are
REPRODUCTION exchanged. 3
HAPLOID ( n )
STAGE
Mitosis
DIKARYOTIC
produces
eight
STAGE Hyphae
7
haploid nuclei.
(n + n) form an
First
meiotic
division
DIPLOID
(2n)
STAGE
Nuclei
Zygote
fuse
Meiosis
6
Meiosis occurs, forming
four haploid nuclei.
Plasmogamy
Nuclei migrate
Dikaryotic
hyphae form
and produce
asci.
4 ascocarp.
Developing
ascus
with
n+n
nuclei
Ascocarp
Karyogamy
5
Mycelium
Karyogamy occurs in each ascus.
Two haploid nuclei fuse, forming a
diploid zygote nucleus.
Fig. 26-13b, p. 567
Insert “Sac fungi”
sac_fungi_m.swf
Basidiomycetes 1
•
Produce sexual spores (basidiospores)
•
•
Basidia develop
•
•
•
on outside of basidium
on surface of gills in mushrooms
a type of basidiocarp (fruiting body)
Hyphae in this phylum have septa
Basidiomycete Fruiting Bodies
Basidiomycetes 2
•
Plasmogamy occurs
•
fusion of 2 hyphae of different mating types
•
Dikaryotic secondary mycelium forms
•
Basidiocarp develops
•
basidia form
Basidiomycetes 3
•
Karyogamy occurs
•
•
Meiosis produces 4 haploid nuclei
•
•
producing diploid zygote nucleus
become basidiospores
When basidiospores germinate
•
form haploid primary mycelia
Basidium with Basidiospores
Basidiospore
Basidium
5 µm
Fig. 26-16, p. 570
Basidiomycetes 4
•
Basidiomycetes include
•
•
•
•
•
mushrooms
puffballs
bracket fungi
rusts
smuts
Basidiomycete Life Cycle
Basidiospore
Basidium
5 µm
Fig. 26-16, p. 570
Insert “Club fungus life
cycle”
club_fungus_life_v2.swf
Explore fungus life cycles by
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KEY CONCEPTS
•
According to current hypotheses, fungi
evolved from a unicellular, flagellate protist
and diverged into five main groups
Learning Objective 7
•
What is the ecological significance of fungi
as decomposers?
Decomposers
•
Most fungi are decomposers
•
•
•
break down organic compounds
dead organisms, leaves, garbage, wastes
into simpler nutrients that can be recycled
Learning Objective 8
•
What is the important ecological role of
mycorrhizae?
Mycorrhizae 1
•
Mutualistic relationships between fungi
and roots of plants
•
Fungus supplies water and nutrient
minerals to plant
•
Plant secretes organic compounds needed
by fungus
Mycorrhizae 2
•
Glomeromycetes form endomycorrhizal
associations with roots
•
Ascomycetes and basidiomycetes form
ectomycorrhizae with tree roots
•
do not penetrate root cells
Mycorrhizal Associations
Learning Objective 9
•
What is the unique nature of a lichen?
Lichen
•
Symbiotic combination of fungus and
photoautotroph (alga or cyanobacterium)
•
Photoautotroph provides fungus with
organic compounds, shelter, water,
minerals
•
Lichens have 3 main growth forms:
crustose, foliose, fruticose
Lichens
Soredia
Surface
layer
(fungal hyphae)
Fungal hyphae
interwoven with
photoautotroph
Loosely
woven hyphae
Rock or other surface
to which lichen is attached
Bottom layer
(fungal hyphae)
Fig. 26-20a, p. 573
Fruticose liche (Ramalina)
Crustose lichens
(Bacidia, Lecanora)
Foliose lichen
(Parmelia)
Fig. 26-20b, p. 573
Insert “Lichens”
lichens.swf
Learn more about lichens by
clicking on the figure in
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Learning Objective 10
•
How do fungi impact humans economically?
Useful Fungi
•
Fungi are used
•
•
•
•
as foods (mushrooms, morels, truffles)
in production of beer, wine, bread (yeasts)
to produce cheeses and soy sauce
to make citric acid and other industrial
chemicals
Edible Ascomycetes
Learning Objective 11
•
What is the importance of fungi to biology
and medicine?
•
How do fungi infect plants and humans?
•
Identify at least three fungal plant diseases
and three fungal animal diseases
Research
•
Fungi are model organisms for molecular
biology and genetics
•
•
•
yeast Saccharomyces cerevisiae
other fungi
Biological control of insects
•
such as mosquitoes that transmit malaria
Medications
•
Fungi are used to make medications
•
penicillin, other antibiotics
Pathogens
•
Fungi are opportunistic pathogens in
humans
•
•
•
•
ringworm
athlete’s foot
candidiasis
histoplasmosis
Toxins
•
Some fungi produce mycotoxins
•
•
such as aflatoxins
cause liver damage and cancer
Fungal Plant Diseases
•
Fungal hyphae infect plants through stomata
•
•
•
hyphal branches (haustoria) penetrate plant cells
obtain nourishment from cytoplasm
Include
•
•
•
wheat rust
Dutch elm disease
chestnut blight
Fungal Infection of Plants
Spore
Hypha
Epidermis
Stoma
Airspace
Leaf
Haustoria
Fig. 26-23, p. 576
Fungal Plant Diseases
KEY CONCEPTS
•
Fungi are of major ecological, economic,
biological, and medical importance