“Zygomycota” Kingdom Fungi. “Zygomycota” Vegetative stage – well developed aseptate hyphae Asexual reproduction by nonmotile sporangiospores Sexual reproduction

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  • ZygomycotaKingdom Fungi

  • ZygomycotaVegetative stage well developed aseptate hyphaeAsexual reproduction by nonmotile sporangiosporesSexual reproduction Zygospore produced in a zygosporangium from fusion of two similar gametangiaCa. 800 spp.

  • ZygomycotaIs polyphyletic has been divided into four subphyla Will discuss major ordersMucorales saprobic (420 spp)Entomophthorales parasites of arthropods (240 spp)Harpellales & Asellariales (Trichomycetes) smaller (135 spp), less well understood, are commensals on surface and in guts of arthropods

  • MucoralesZygospore production is generally similar among species, therefore classification is based on characteristics of asexual reproductive structuresAsexual reproduction is typically by production of sporangiospores, but we will see lines of evolution in which the number of spores/sporangium is reduced until there is only 1 spore/sporangium - conidium

  • MucoralesGrow saprotrophically on decaying plant and animal remains in soils, dung, etc.Produce large numbers of asexual spores that are dispersed in the airCommon contaminants in laboratorySome are important in spoiling food common bread mold, storage diseases of fruits and vegetablesSome infect humans and animals opportunistic pathogens

  • MucoralesTypically form aseptate hyphae, septa formed to delimit reproductive structuresSome species form rhizoids

  • Multispored sporangiumMorphology of sporangia varies, basis for classificationTypical multispored sporangium containsSporangium wallColumellasporangiophore

  • Development of sporangiumTip of sporangiophore swells Swelling increases, contains multinucleate cytoplasmCytoplasm is cleaved to form all spores at one time cell membrane and cell walls laid down around nuclei

  • Development of sporangiaAfter formation, sporangial wall may break and release spores into the air orA drop of fluid may envelop the sporangium with spores being dispersed by small animals that touch the sporangium

  • Reduction of sporangium Several lines of evolution in the reduction of number of spores/sporangiumExamples of modifications of sporangiaThamnidium both multispored sporangium and smaller sporangia = sporangiola

  • Reduction of sporangiaBlakeslea sporangiola with 3 spores/sporangiolumCunninghamella one spore/sporangiolum, spore wall and sporangiolum wall indisdistinguishable except with EM

  • Reduction of sporangiaOne group in the Mucorales produce cylindrical sporangia = merosporangiaAlso see a reduction in the number of spores/sporangium in this lineSyncephalastrum

  • Other sporangial modificationsPilobolus fungal shotgunGrows on herbivore dungSporangiophore contains carotenoids, acts as a lens to focus light and direct the growth of the sporangiophore to point the sporangium at light source

  • PilobolusAs the sporangium and sporangiophore mature, the sporangiophore builds up a very high turgor pressureSporangium as a whole is shot off suddenly, directly at the light up to 3 mA drop of fluid on the sporangium causes it to stick to whatever it hitsPhototrophic ability allows sporangium to be shot out of a pile of dung, land on grass, be eaten by herbivores

  • PilobolusPassage through gut of herbivore activates spore germinationSporangium is dark in color to prevent damage from UV when attached to grass

  • Sexual reproductionInvolves fusion of two multinucleate gametangia that are similar in structure, may differ in sizeGametangia are produced as terminal swellings of hyphal branchesAfter plasmogamy a thick walled zygospore is produced with a zygosporangiumBoth homothallic and heterothallic species

  • Life cycleVegetative mycelium is haploid, reproduces asexually by producing sporangiospores in sporangiaIn a heterothallic species, when two compatible strains come together, hyphal branches form, enlarge to form progametangia

  • Life cycleSepta form, producing multinucleate gametangia and suspensors

  • Life cyclePlasmogamy occurs, end walls of gametangia dissolve and cytoplasm of gametangia mixes

  • Formation of zygospore

  • Life cycleZygospore forms inside zygosporangiumZygospore develops thick wall, warty appearance, dark in colorKaryogamy occurs at different times in zygospore formation in different species, so zygospore is diploid at some point

  • Life cycleWhen zygospore germinates, meiosis occurs to start the haploid portion of the life cycle over again

  • Life cycle

  • Variation in zygosporesSome variation is seen in zygospore formation

  • EntomophthoralesArthropod parasites, 240 spp.Asexual reproduction by one spored sporangiola (conidia)Mycelium exhibits limited growth in the body of the host, forms septa and fragmentsEntomophthora is a parasite of flies seen when fly is stuck to window, white halo around it

  • EntomophthoraMycelium fills up body of fly, forms sporangiophores that extend out of segments of abdomen

  • EntomophthoraSporangiophore builds up pressure, shoots off sporangiolum when there is air movement (another fly)If misses, can form another structure that shoots it off, up to 3 timesSexual reproduction not well understood, form resting spores that are similar to zygospores

  • Entomophthorales

  • GlomeromycotaObligate biotrophsBiotrophic in the roots of higher plants, form arbuscular mycorrhizaeCa. 169 spp.

  • GlomeralesForm tree-like structures = arbuscules in cells of plant exchange of nutrients between fungus and plantForm large spores in soil azygospores, and chlamydospores depending on species

  • GlomalesAzygosporesChlamydospores

  • Phylogenetic relationships

  • TrichomycetesAll but a few species are obligate commensals in guts or on exoskeleton of arthropodsFound in freshwater (mayfly, stonefly, midges) and terrestrial (millipedes)

  • TrichomycetesThallus is relatively simple produce a holdfast that anchors them to lining of gut

  • TrichomycetesThallus may be unbranched and aseptate or branched and septateVariety of asexual spores produced (generally 1 spore/sporangium)

  • TrichomycetesSexual reproduction involves formation of zygospores (in one order)Fusion of cells in thallusFormation of zygosporophore and then zygospore

  • Lower fungiMajor groups of lower fungi Chytridiomycota, Blastocladiomycota, Neocallimastigomycota, Zygomycota, Glomeromycota (Oomycota)Exhibit diversity in vegetative thallus, asexual and sexual reproductionMycelium when present is typically aseptateUsed to be placed in one class = Phycomycetes now clear that they do not share a common phylogeny

  • Lower fungiAsexual reproduction spores produced inside a sporangium sporangiosporesIn Chytridiomycota, Blastocladiomycota, Neocallimastigomycota, and Oomycota, zoospores producedTransition from multispored sporangia to conidia in both the Oomycota and Zygomycota

  • ReproductionAsexual - Sporangia produce sporangiospores, in some zoosporesSexual Life cyclesHaploid life cycles Zygomycota produce zygospore, isogametangiaDiploid life cycles Oomycota produce oospore, oogonia and antheridiaHaploid Diploid life cycles Allomyces,