Filamentous fungi - a background
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Transcript of Filamentous fungi - a background
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Filamentous fungi -a backgroundLecture 1 and 2 What are they?What are they doing?
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Fungi are important in nature
As decomposersAs pathogens of plants, animals and humans, and in food spoilageAs producers of secondary metabolites, e. g. penicillinIn cheese, bread and wine making
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Fly agaric(flugsvamp)
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Ergot of ryeCaused by Claviceps purpurea.Cause of ergotism: Holy Fire or St. Anthonys Fire.Sclerotia are dangerous.Witch hunts.Caused low fertility and death in 14th-18th century Europe.
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Other toxins made by fungiEndophytic fungi (Acremonium) in grasses can be toxic to cattle (fescue toxicosis)Other mycotoxins:OchratoxinsAflatoxins - carcinogenicFumonosins - blind stagger of horsesPatulin - bleeding in lungs and brain, kidney damage, cancer
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Medicines that come from fungiPenicillin. Penicillium chrysogenum. Alexander Fleming, 1928.CephalosporinCyclosporin
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Fungal diseases of humans - mycosesTrichophyton rubrum. Causal agent of athletes foot. Came from tropics.Candida albicans. Causes candidiasis = yeast infections. Around genitalia. Disease of mouth and throat.Blastomycosis, Cryptococcosis, Histoplasmosis, Aspergillosis are other diseases.
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Smut infection of a wheat field inEastern Washington (1956)
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Ustilago maydis - the corn smut fungus
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Ustilago maydisis a popular fooddelicacy in Mexico
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Examples of symptoms caused by fungi:CankersStorage rots of fruits and vegetablesRust, mildewsLeaf spots
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Pathogen life stylesNecrotrophs - kill host cells with toxins and hydrolytic enzymes.Ex: Botrytis cinerea.Biotrophs - specialize on a living host.Ex. Powdery mildews and rusts.Hemibiotrophs - start out biotrophic. Then, they kill the host cells. Ex. Phytophthora infestans.
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Botrytis cinerea - a fungus -causes grey mold
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Grey mould of strawberries
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Characteristics of grey moldB. cinerea is a necrotroph, entering the plant through dead or dying tissue.It is a pathogen that attacks almost any known plant species. It invades healthy tissue through dead petals or leaves or dying wood.
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Botrytis cinerea causes rots on fruits and vegetables, blossom blights, damping off, stem cankers, leaf spots and bulb rots.scleriotia
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In the field, blossom blight often precede the fruit rotsThe fungus enters the fruit through the dead flower petals.
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The fungus Botrytis cinereaDevelops grey mycelium with long, branched conidiophores with clusters of one-celled, ovoid conidia.The conidiophores and conidia resemble a grapelike cluster.
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Botrytis cinerea of tomato
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Botrytis cinerea of tomatoSpots on fruits are from spores that have landedAttack on fruit originated in the flower
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Grey mould - continuedB. cinerea overwinters as mycelium in decaying plant debris or as sclerotia - black, hard resting structures.It also attacks fruit and vegetables during storage. The fruits rot internally (often from the flower end) and a soft mycelial mat develops on the surface. The fungus does most damage when it is very humid and damp.
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Life cycle of Botrytis cinerea
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Powdery mildew on roseSphaerotheca pannosa is the causal agent of powdery mildew on roses. It is an example of a biotroph: It grows only in living plant tissue.The white, powdery appearance is due to conidiophores/conidia
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Powdery mildew on Poinsettia
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Powdery mildew on squash
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Powdery mildew on cucumber
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Life cycle of powdery mildew
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Rust of roen (rnn)
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Rust of raspberry
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Rust of rose
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Four phyla of fungiChytridiomycota - no sexual sporeZygomycota - zygosporeAscomycota - ascosporeBasidiomycota - basidiospore
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Characteristics of fungiFungi have hyphae. A mass of hyphae is a mycelium. The hyphae may be septate or aseptate.Specialized hyphae, haustoria are feeding structures.
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Fungal reproductionAsexually, by forming conidiaSexually (three steps):Plasmogami (dikaryon)Karyogami (zygote forms)Meiosis (sexual spore forms):ZygosporeAscosporeBasidiospore
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Incompatibility systemsFungi (ascomycetes) have mating types. They are designated MATa and MATa (yeast), MATA and MATa (Neurospora) or MAT1-1 and MAT1-2. Sexual reproduction in a heterothallic ascomycete requires the participation of different mating types. In a homothallic strain the fusing individuals are of the same mating type. The inability of two individuals of the same mating type to fuse is called vegetative incompatibility.
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Chytridiomycota
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Zygomycota
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Gametangia fuse to produce a zygospore (Rhizopus stolonifer)
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Ascomycota
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Penicillium and Aspergillus
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Examples of conidiophores of other imperfect fungi or Deuteromycetes