Phylum Zygomycota Classes Sexual Reproduction Asexual

Phylum Zygomycota Classes Sexual Reproduction Asexual

Classes
Zygomycetes
870 species in 124 genera, 32 families and
10 orders
Phylum Zygomycota
Trichomycetes
218 species in 55 genera, 6 families and 3
orders
4032604 Lecture 16
Sexual Reproduction
Mycelium
plasmogamy
Progametangia
Suspensors
karyogamy
Sexual reproduction by production of
zygospores (=thick-walled resting
spores) within zygosporangia that are
formed by fusion of gametangia
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Gametangia
Zygospore
Zygote
Asexual Reproduction
Sporangia
Sporangiospores delimited from cytoplasm
by cleavage vesicle fusion
Conidia
Formed by same mechanism as
blastoconidia
http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Mo
ulds/Zygospores_of_Mucorales.html
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Class Zygomycetes
Orders to be covered:
Mucorales
Kickxellales
Dimargaris
Zoopagales
Entomophthorales
Glomales
Order Mucorales
Well developed, typically coenocytic
mycelium
Wall composition of chitosan, chitin and
polyglucoronic acid
Asexual reproduction by formation of
sporangiospores cleaved out from the
cytoplasm of sporangia
Chlamydospores may be formed
Called mucoralean or mucoraceous fungi
Mucor
Sporangia
Most taxa produce globose sporangia
Sporangial wall can be persistant or
fragile, of various colors, and is usually
smooth
sporangiospores
columella
sporangium
sporangiophore
http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds.html
Sporangia
Apophysate
Subsporangial
swelling
Nonapophysate
Lacking
subsporangial
swelling
Sporangiospores
One-celled
1- to multinucleate
Smooth-walled, or ornamented with
spines, warts or striations
Most taxa produce hyaline spores
Some taxa produce spores with hyaline
appendages
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Sporangiolum
Sporangium
containing 1-50
spores
Merosporangium
is a sporangiolum
with spores in
linear series
Rhizopus
stolons
rhizoids
http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds.html
No columella
Mortierella
Rhizopus
From Bioimages
http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds.html
Pilobolus
Common fungus sporulating on
dung
Sporangia with dark, thick,
persistant wall
Characterized by forcibly
discharged sporangia (> 2 meters!)
Sporangiophores are phototropic (bend
towards light)
sporangium
sporangiophore
substrate
trophocyst
Pilaira—similar morphology and
ecology, lacks discharge mechanism
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Photo by Marco Hernandez-Bello
Photo by Marco Hernandez-Bello
Sexual Compatibility
Regulated by trisporic acid, a sex pheromone
(Blakeslee, 1904):
Enhances secretion of specific precursors of
trisporic acid and beta-carotene
Positively regulates its own synthesis by
stimulating rate of precursor formation in paired
cultures
Induces zygophore formation
Represses sporangiophore formation
Zygospores
Thick-walled, usually hyaline, but
zygosporangium wall often pigmented
and ornamented
One zygospore per zygosporangium
Germination by formation of hyphae or
sporangium
Ecology
Saprotrophs
Soil, dung, humus
Plant pathogens
Choanephora cucurbitarium
• on flowers & fruits of cucurbits
Rhizopus stolonifer
• Post-harvest pathogen of strawberries, sweet potatoes
Animal pathogens
Species of Absidia, Mucor, Rhizopus, Saksanea
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Industrial applications
Industrial production of amylases,
rennins, secondary metabolites and
organic acids
Production of Asian Foods
Tofu or sufu (Chinese cheese)
A soft cheese-type product made from cubes
of soybean curd using fermentation by
Actinomucor elegans
citric, fumaric, lactic and succinic acids
Tempeh
A solid cakelike product from soybeans
fermented with Rhizopus oligosporus
Order Kickxellales
One family and eight genera
Characterized by one-spored
sporangiola formed on pseudophialides
borne on sporocladia
Extensively branched, septate mycelium
Saprotrophs, common in soil and dung
pseudophialides
merosporangia
sporocladia
From O’Donnell 1979
Order Dimargaritales
One family and four genera
Characterized by 2-spored
merosporangia formed on terminal
inflated ampullae
Produce branched, septate hyphae with
unusual, dumbbell-shaped septal plugs
Obligate mycoparasites of mucoraceous
fungi
From O’Donnell 1979
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Order Zoopagales
Dimargaris
Five families, 21 genera, 163 species
Coenocytic or septate hyphae
Conidia or multispored merosporangia
All members are obligate parasites of other
fungi or microscopic animals (amoebae,
rotifers, nematodes)
Ectoparasitic, endoparasitic or predaceous
Haustoria formed in host in ectoparasitic and
predaceous species
From O’Donnell 1979
Syncephalis (11) and Piptocephalis (12)
From O’Donnell 1979
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