Zygomycota
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| Zygomycota Zygomycota About 1%, ~ 1000 species of the named species of true fungi
Mucor, Rhizopus Many are common on dung of various animals Pilobolus, Phycomyces, Coemansia Others have highly specialized symbioses Endogone, ectomycorrhizal Zoopagales, parasites of rotifers, tardigrades Entomophthorales, parasites of insects Harpellales & Asellariales ( Trichomycetes ),
specialized gut commensals of arthropods Some Mucorales are mycoparasites
Relationship of the Zygomycota to the other phyla of Fungi is not completely clear and relationships of taxa within the Zygomycota are now being revised Four subphyla currently recognized in the Zygomycota: Mucormycotina Entomophthoromycotina Kickxellomycotina Zoopagomycotina (formerly orders Mucorales, Entomophthorales, Zoopagales) Two main groups but do not correspond to the two classes Zygomycetes and Trichomycetes Zygomycota Formerly two Classes based on morphology and ecology: Zygomycetes Wide diversity of forms Various ecological modes Saprobes, soil and dung Parasites of small animals, insects Parasites of other fungi Opportunistic human/animal pathogens Fruit/grain rots Ectomycorrhizal (Endogonales) Trichomycetes (Harpellales, Asellariales) Specialized parasites of arthropods
Zygomycota orders Mucorales Rhizopus Pilobolus Phycomyces Mortierellales Mortierella Dimargaritales Piptocephalis Kickxellales Coemansia, Spirodactylon Endogonales Endogone Entomophthorales Entomophthora Zoopagales Amoebophilus Euryncale Harpellales e. g. Furcuolmyces boomerangus General characteristics of Zygomycota • Primitive early diverging fungal lineage • <1% of all known species of fungi, ~1000 species • primary colonizers of most substrates sugar fungi • most species have thallus of coenocytic hyphae • haploid nuclei in vegetative stage • chitin cell walls • no flagellated cell • no centrioles; possess spindle pole bodies (SPBs)
Ecological diversity of Zygomycetes Saprobes in soil and dung Mucorales, Mortierellales, Kickxellales Parasites of invertebrates, insects, rotifers, amoebae Entomophthorales, Zoopagales Mycoparasites Mucorales, Dimargaritales, Zoopagales Ectomycorrhizal Endogonales Human pathogens Mucorales, Entomophthorales Obligate gut parasites of arthropods Trichomycetes (Hapellales) Importance of Zygomycetes Used in soy fermentations Rhizopus oligosporus tempeh Actinomucor elegans tofu Human and animal pathogens Basidiobolus and others, mucormycoses Storage rots of fruits Rhizopus stolonifer Plant pathogens Gilbertella, Rhizopus (endosymbiotic Burkholderia) Bioinsecticides, biocontrol Entomophaga maimaga Sexual reproduction by production of zygospores (=thick-walled resting spores) within zygosporangia that are formed by fusion of gametangia, hyphal branches • zygos (Gr.) - yoke, joining • refers to the fusion of gametangia to form a unique
www.botany.hawaii.edu/faculty/wong/Bot201/Zygomycota/Zygomycota.htm zygosporangium suspensors Zygosporangia mating in Zygomycetes by isogamous hyphal fusion Sexual reproduction • gametangial copulation, somatogamy • conjugation by two morphologically similiar gametangia • gametangia are differentiated hyphal branches • differentiation in Mucorales controlled by pheromones • produce a zygosporangium • homo- & heterothallic species (unifactorial) botit.botany.wisc.edu/images/332/Zygomycota/ zygosporangium gametangia • formation of specialized hyphae: zygophores • compatible zygophores are attracted to each other by pheromones of the opposite mating type, trisporic acids • fuse in pairs at their tips; form fusion septum • tips of zygophores swell to form progametangia
• gametangial septum forms near tips of progametangia • terminal cell is gametangium • subterminal cell is suspensor cell
• fusion septum dissolves • plasmogamy results in prozygosporangium • followed by karyogamy, enlargement, development of thick
Zygospore germination • zygospore doesn't equal zygosporangium produced within zygosporangium • typically long resting period prior to germination • zygosporangium cracks open zygospore germinates a sporangiophore that develops a germ sporangium • meiosis occurs before or during zygospore germination followed by numerous rounds of mitosis • germ sporangium produces sporangiospores that are dispersed, germinate, & produce a mycelium Rhizopus life cycle germ sporangium asexual reproduction asexual reproduction sexual reproduction mating type + mating type - Progametangia Mycelium + -
Suspensors Zygote
Zygosporangium plasmogamy Zygomycete pheromones, trisporic acids + and – mating types produce phermones that are converted to trisporic acid by the opposite mating type Sexual compatibility in Rhizopus A.F. Blakeslee 1904 first example of sexual incompatibility in fungi somes species could only produce zygospores when paired with certain isolates designated +/- Burgeff 1924 First demonstration of pheromones in fungi hormonal substance responsible for incompatibility trisporic acid each strain produces precursor molecules that the compatible strain converts to trisporic acid (TSA) TSA triggers positive feedback & production of more precursor results in maturation of gametangia and gametangial fusion Induces zygophore formation Represses sporangiophore formation
Zygomycete pheromones B-carotene, trisporic acid Asexual Reproduction • Sporangia – Sporangiospores delimited from cytoplasm by cleavage vesicle fusion, similar to free cell formation • Sporangiola – Reduced sporangia having one or a few sporangiospores. Single sporangiola resemble conidia. • sporangioles reduced sporangia with or w/o columella produce one to few spores • sporangia and sporangioles can be formed on the same sporangiophore sporangiospores asexual reproduction some sporangiospores look like conidia, but have an outer sporangial wall--derived from larger multi-spored sporangia Phylum Zygomycota
• 10 Orders, ~168 genera, ~1000 species – Mucorales – Mortierellales – Endogonales – Kickxellales – Dimargaritales – Basidiobolales (Basidiobolaceae) – Zoopagales – Entomophthorales – Harpellales – Asellariales
MUCORALES largest order, 47 genera, 130 species most common species used in industry and food production Rhizopus spp. used in industry fumaric, lactic, citric, succinic & oxalic acids food production tempeh Structures • coenocytic hyphae • septa associated only with reproductive structures • rhizoids: root-like hyphae that adhere reproductive structures to substrate • stolon: connect two groups of rhizoids rhizoids stolon Sporangia of Phycomyces Phototropic sporangia have been used as model systems for study of photorecptors • sporangiophores simple to branched • sporangium: +/- columella with outer sporiferous region • sporangium produces thousands of sporangiospores
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www.uoguelph.ca/~gbarron/MISCELLANEOUS/rhizopus.htm
Mucor sporangium columella sporangiospores sporangiophore Sporangiolum • A reduced sporangium containing 1-50 sporangiospores • Merosporangium is a sporangiolum with spores in linear series
Ecology • Saprotrophs – Soil, dung, humus • Plant pathogens – Choanephora cucurbitarium • on flowers & fruits of cucurbits – Rhizopus stolonifer • Post-harvest pathogen of strawberries, sweet potatoes • Animal/human pathogens – Species of Absidia, Mucor, Rhizopus,
mucormycoses • Mycoparasites on various other fungi
Pilobolaceae Pilobolus (hat thrower) • sporangiophore extending from substrate • end of sporangiophore is a swollen
• sporangium sits on top of the ssv • ssv is directed towards light by carotenoid ring • ssv acts as lens concentrating light rays • pressure builds up in the ssv, propelling the sporangium
• sporangium sticks vegetation • sporangia are ingested by animal, pass through GI
Thamnidium
Sporangia and sporangiola on the same sporangiophore Syncephalastrum
Merosporangia - sporangiospores in linear series Syncephalis (11) and Piptocephalis (12) merosporangia Choanephora and Cunninghamella Sporangiola formed on separate sporangiophores
Entomophthorales • parasites on insects • Entomophthora muscae on common house fly • conidia actively dispersed • some have septate mycelium; break into hyphal bodies (hb)
• hb germinate to produce asexual spores • two hb may act as gametangia, copulate, lateral outgrowth develop into zygosporangium containing a zygospore www.uoguelph.ca/~gbarron/MISCELLANEOUS/ento2.htm conidia hyphal body www.mycolog.com/CHAP3b.htm Entomophthora maimaga Being used as a biopesticide to control gypsy moth Etienne Leopold Trouvelot Settled in Medford Mass. in 1853. He was an amateur entomologist and wanted to start a silk industry in the USA. He introduced the European Gypsy Moth after a visit to France in the 1860s. Larvae escaped from the population he was tending on trees in his back yard, after which he apparently lost interest in entomology and took up astronomy. Trouvelot later worked at Harvard University and the Naval Observatory (now where the vice president lives) Family Basidiobolaceae 1 Genus, 4 species
Basidiobolus, saprobic, also cause of subcutaneous zygomycosis in humans Order Kickxellales • One family, 8 genera, 22 species • Characterized by one-spored sporangiola formed on pseudophialides borne on sporocladia • Extensively branched, septate mycelium • Saprotrophs, common in soil and dung
From O Donnell 1979 merosporangia pseudophialides sporocladia Order Zoopagales Mycoparasites and parasites of small animals Predaceous fungi Amoebophilus simplex Zoophagus insidians Conidia of Euryancale are adapted to lodge in the buccal cavity of the nematode, have adhesive frill for attachment once it is ingested Piptocephalis and Syncephalis
Biotrophic, haustorial mycoparasites, mainly of Mucoraceae Order Dimargaritales • One family, 4 genera, 14 species • 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 – Biotrophic, haustorial Order Endogonales Endogonaceae Endogone a zygomycetous truffle, pea truffle ectomycorrhizal sporocarps contain zygospores Order Zoopagales • 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 Class Trichomycetes Molecular studies show not really a separate class under revision 2 Orders, 55 Genera, 220 species • obligately associated with living arthropods often aquatic arthropods insects, millipedes, crustaceans • attach to the hindgut via a holdfast • grow within the hindgut of their hosts
• mostly commensals, some beneficial or antagonists • many species produce septate hyphae Trichomycetes Harpellales Smittium Zygomycota Attach to hindgut of various aquatic arthropods Sexual spores - zygospores Asexual spores - trichospores Harpellales attach to hindgut of various arthropods, mainly aquatic insect larvae, also, millipedes, terrestrial beetles, fiddler crabs Yüklə 79,83 Kb. Dostları ilə paylaş:
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