There are three distinct domains of life
BioV 400
Mycology
Handout 2
Woese (1994) Microbiological Reviews, 58, 1-9. Woese (2002) P.N.A.S. USA, 99, 8742-7.
What is a fungus?
Fungi in Evolutionary Context
• Fungi are probably evolved from a
unicellular protist with a flagellum
• The common ancestor of fungi and animals
may have been similar to today’s
choanoflagellates
• Choanoflagellates, fungi, and animals form
a clade  the opisthokonts
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Choanoflagellates
Bacteria transform the closest living relatives
of animals from single cells into colonies
• Microscopic, heterotrophic singlecelled and colony-forming eukaryotes
• Occupying diverse freshwater and
marine ecosystems
• Closest unicellular relatives of animals
 insights into the origin and
diversity of animal phyla
• The marine choanoflagellate
Monosiga brevicollis  genome
project  easily grown in the
laboratory
Phylogeny of the Fungi
Three main groups
• Slime moulds (myxomycetes or mycetozoa)
Wall-less protoplasm, engulf bacteria, produce
spores, etc.
• Oomycota
Plant-like features, cellulose in their walls, typical
fungal lifestyle, plant pathogens, etc.
• True fungi
Chitin in their walls
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Growth forms of fungi
True fungi
eukaryotic, mycelial heterotrophs
with reproduction by spores
• Eukaryotic with membrane bound nuclei
and cytoplasmic organelles
• Typically filame ntous: hyphae and mycelia
• Heterotrophs (chemo-organotrophs), no
phagocytosis, absorption of nutrients
• Reproduce sexually and asexually, the
spores being the end-product
Charateristics of chitin-walled true fungi
Character
True fungi
Animals
Oomycota
Growth habit
Hyphal, tip
growth
Not hyphal
Hyphal, tip
growth
Nutrition
Heterotrophic
absorpti ve
Heterotrophic
ingestive
Heterotrophic
absorpti ve
Cell wall
Chitinous
Chitin in insect
exoskeleton
cellulose
Haploid
Diploid
Diploid
Nuclei
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Charateristics of chitin-walled true fungi
Character
True fungi
Animals
Oomycota
Histones
Histone-2B like
animals
Histone -2B
Like plants
Microtubules
Sensitive to
griseofulvin
Sensitive to
colchicine
Sensitive to
colchicine
S torage
compounds
Glycogen,
Glycogen,
Glucose
lipids, trehalose lipids,trehalose
Mt codon
usage
UGA trp
UGA trp
UGA stop
Slime molds
Major groups
• True fungi
Chytridiomycota, Zygomycota, Glomeromycetes,
Ascomycota, Deuteromycota, and Basidiomycota
• Fungus-like organis ms (behaviour and
lifestyle)
Oomycota
• Fungus-like organis ms (some features)
Wall-less Slime moulds
Cellular Slime Mold
• Life cycle of cellular slime molds
– Amoeba stage  Germinate from a spore
– Slug stage  Many amoebas aggregate and
sheath forms  Migration
– Fruiting body  Releases spores which
germinate into amoebas
• Plas modial (acellular) slime molds
– Mass of protoplasm with many nuclei
(plasmodium)
– Capable of sexual reproduction
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Acellular slime molds
Slime Mold plasmodium (Physarum)
Sporangia
Oomycota
• Resemble fungi in behaviour and lifestyle
• Cellulose based walls and cellular features
resembling those of plants
• Hyphae aseptate
• Asexual reproduction by formation of
biflagellate zoospores in a sporangium
• Sexual reproduction by fusion of
antheridium and oogonium  oospores
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Phytophtora infestans
(gametangium)
Saprolegnia
Pythium
Life cycle of Oomycota
Oomycota the cellulose-walled
fungi
• Phytophtora, Pythium, Saprolegnia, etc.
• P. infestans life cycle: opposite mating types
 sex organs (antheridium and oogonium)
 fertilization  thick-walled oospores 
germination  hyphal outgrowth 
sporangia (wind dispersed landing on
leaves)  direct germination or production
of zoos pores (which initiate infection) 
production of sporangia
Things to Know about Oomycete
Fungi
• Wate r molds or mildews
• Cause diseases such as potato blight
• Cell walls made of cellulose (like plant)
• Hyphae have multiple nuclei! Because the
cell walls do not fully close off
• Spore swims away like a flagellate, which is
why it is protist like (think of Euglena)
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Fungi
•
•
•
•
•
Chytridiomycetes or chytrids
Aquatic, flagellated fungi
Closely related to ancestral fungi
Have motile zoospores
Batrachochytrium dendrobatidis has been
implicated in amphibian die-offs
Discoloration caused by late blight
infection in a potato tuber
Ascomycota
Basidiomycota
Chytridiomycota
Glomeromycota
Neocallimastigomycota
Zygomycota
Microsporidia
Chytridiomycota
Blastocladiomycota
Potato late blight mycelium on the leaves
of an infected potato plant
True fungi: Chrytridiomycota
• Typically unicellular
• Primitive chains of cells attached to a food
base by rhizoids
• Sexual reproduction by motile gametes
• Asexual reproduction by cytoplasmic
cleavage in a sporangium  motile
uniflagellate zoospores
• Aquatic, flagellated fungi
• Most closely related to ancestral fungi
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Chytridyomycota
Allo myces
Olpidiu m brassicae
Rhizophlyctis rosea
• Allomyces, Olpidium, Rhizophlyctis, etc.
• Allomyces life cycle: haploid thalli produce
motile gametes  fusion in pairs (diploids)
 encyst (zygotes)  germinate  diploid
thalli  sporangia  germinate to repeat
the diploid phase  thick-walled resting
sporangia (adverse conditions)  meiosis 
haploid zoospores  haploid thalli
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True fungi: Zygomycota
• Zygomycota (Conjugation Fungi)
• Includes common bread molds
• Saprophytic molds with coenocytic hyphae 
aseptate hyphae
• Asexual reproduction  used most of the time
– Asexual reproduction by cytoplasmic cleavage in a
sporangium  non-motile spores
– S porangiospore  asexual spore enclosed within a
sporangium or sac at the end on an aerial hypha
True fungi: Zygomycota
• Sexual reproduction by fusion of gametangia 
zygospores
– Sexual Reproduction  occurs through conjugation,
the joining of hypha of two different strains (+ and -)
– Zygospores  sexual spores which are enclosed in a
thick, resistant wall  dormant zygosporangia
• Generally not pathogens
• Rhizopus nigricans
– Common black bread mold
– May cause opportunistic infections in diabetes patients
Mucor
Entomorphtora
Piptocephalis
Pilobolus
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Zygomycota
• Mucor, Pilobolus, Erynia, Pitocephalis, etc.
• Life cycle of Mucor: somatic hyphae 
sporangiophores and sporangia  spores
are released and germinate into somatic
hyphae  opposite mating types produce
zygophores (aerial branches) 
progametangia  terminal gametangia 
fusion  thick-walled resting spores
(zygos pore)  meiosis  germination into
sporangiophore or hypha
Life cycle of the zygomycete Rhizopus
Asexual Reproduction
Sexual Reproduction
Zygosporangium
matures.
Spore germinates
to produce aseptate
mycelium (1n).
Vegetative
mycelium
grows.
Sporangium
bursts to
release spores.
The life cycle of Rhizopus
Nuclear meioses occurs
(not shown).
Zygosporangium
forms. (2n)
Zygospore
(2N)
Zygosporangium
produces an
asexual sporangium
(1n).
FERTILIZATION
Sporan gium
Gametangi a
Mating hyphae
join and fuse.
Dikaryon
(n n)
Haploid nuclei (1n)
Sporangium
(1n)
MEIOSIS
Sporan gium
Spores (N)
Gamete
forms at
tip of
hypha.
Spores
(N)
Zygospore (2 N)
Sporangiospores
Sporangiophore
Aerial hypha
produces a
sporangium.
Spores (1n)
are released
from
sporangium.
Stolons
+ Mating type (N)
- Mating type (N)
Sporan gio phore
Spore germinates.
Asexual
Reproduction
Rhizo ids
Sexual Reproduction
Dipl oid
Hapl oid
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True fungi: Ascomycota
• Ascomycota (Sac Fungi)
• Septate hyphae or yeasts
• Sexual reproduction by fusion of modified
hyphae or yeasts (haploids)
Fusion of a spermatium (♂ spore) and trichogyne
(♀ receptive hypha)  ascus with ascospores
• Asexual reproduction by non-motile spores
or conidia
Severe nail infection with Trichophyton rubrum in
a 37-year-old male AIDS patient
True fungi: Ascomycota
• Asexual Reproduction  conidiospores
– Not enclosed in a sac
– Become airborne easily
– Form chains (broom-like structures )
• Include common antibiotic producing fungi and yeasts,
and several human pathogens
–
–
–
–
–
–
Penicillium notatum (Produces penicillin)
Saccharomyces (Brewer’s yeast)
Trychophyton (Athlete’s foot)
Aspergillus (Carcinogenic aflatoxin in peanuts)
Blastomyces (Respiratory infections)
Histoplasma capsulatum (Respiratory and systemic infections)
Neurospora crassa
Eurotium
Ascobolus
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Ascomycota
• Neurospora, Eurotium, Ascobolus,
Saccharomyces, etc.
• Life cycle of Neurospora: somatic hyphae 
conidiophores and conidia  germination
into somatic hyphae  spermatium (♂
spore) or normal conidium + trichogyne 
ascus (enclosed in ascocarp)  nuclear
fusion and meiosis (+ one mitosis)  8
haploid spores
Life cycle of the yeast
S. cerevisiae
Life cycle of the haploid, mycelial-form fungus Neurospora crassa
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Ascomycota  “sac fungi” or “cup fungi”
Scarlet cup
Morels
Truffles
Truffles
 Are round, warty, fungi
that are irregular in shape
 Vary from the size of a
walnut to that of a man's fist
 Most expensive of the
world's natural foods, often
commanding as much as
$250 to $450 per pound
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