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Filamentous fungi - a background

Filamentous fungi - a background. Lecture 1 and 2 What are they? What are they doing?. Fungi are important in nature As decomposers As pathogens of plants, animals and humans, and in food spoilage As producers of secondary metabolites, e. g. penicillin In cheese, bread and wine making.

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Filamentous fungi - a background

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  1. Filamentous fungi -a background Lecture 1 and 2 What are they? What are they doing?

  2. Fungi are important in nature • As decomposers • As pathogens of plants, animals and humans, and in food spoilage • As producers of secondary metabolites, e. g. penicillin • In cheese, bread and wine making

  3. Fly agaric(flugsvamp)

  4. Ergot of rye • Caused by Claviceps purpurea. • Cause of ergotism: “Holy Fire” or “St. Anthony’s Fire”. • Sclerotia are dangerous. • Witch hunts. • Caused low fertility and death in 14th-18th century Europe.

  5. Other toxins made by fungi • Endophytic fungi (Acremonium) in grasses can be toxic to cattle (fescue toxicosis) • Other mycotoxins: • Ochratoxins • Aflatoxins - carcinogenic • Fumonosins - blind stagger of horses • Patulin - bleeding in lungs and brain, kidney damage, cancer

  6. Medicines that come from fungi • Penicillin. Penicillium chrysogenum. Alexander Fleming, 1928. • Cephalosporin • Cyclosporin

  7. Fungal diseases of humans - mycoses • Trichophyton rubrum. Causal agent of athlete’s foot. Came from tropics. • Candida albicans. Causes candidiasis = yeast infections. • Around genitalia. • Disease of mouth and throat. • Blastomycosis, Cryptococcosis, Histoplasmosis, Aspergillosis are other diseases.

  8. Smut infection of a wheat field in Eastern Washington (1956)

  9. Ustilago maydis - the corn smut fungus

  10. Ustilago maydis is a popular food delicacy in Mexico

  11. Examples of symptoms caused by fungi: • Cankers • Storage rots of fruits and vegetables • Rust, mildews • Leaf spots

  12. Pathogen life styles Necrotrophs - 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.

  13. Botrytis cinerea - a fungus -causes grey mold

  14. Grey mould of strawberries

  15. Characteristics of grey mold • B. 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.

  16. Botrytis cinerea causes rots on fruits and vegetables, blossom blights, damping off, stem cankers, leaf spots and bulb rots. scleriotia

  17. In the field, blossom blight often precede the fruit rots The fungus enters the fruit through the dead flower petals.

  18. The fungus Botrytis cinerea Develops grey mycelium with long, branched conidiophores with clusters of one-celled, ovoid conidia. The conidiophores and conidia resemble a grapelike cluster.

  19. Botrytis cinerea of tomato

  20. Botrytis cinerea of tomato Spots on fruits are from spores that have landed Attack on fruit originated in the flower

  21. Grey mould - continued • B. 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.

  22. Life cycle of Botrytis cinerea

  23. Powdery mildew on rose • Sphaerotheca 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

  24. Powdery mildew on Poinsettia

  25. Powdery mildew on squash

  26. Powdery mildew on cucumber

  27. Life cycle of powdery mildew

  28. Rust of roen (rönn)

  29. Rust of raspberry

  30. Rust of rose

  31. Four phyla of fungi • Chytridiomycota - no sexual spore • Zygomycota - zygospore • Ascomycota - ascospore • Basidiomycota - basidiospore

  32. Characteristics of fungi Fungi have hyphae. A mass of hyphae is a mycelium. The hyphae may be septate or aseptate. Specialized hyphae, haustoria are feeding structures.

  33. Fungal reproduction • Asexually, by forming conidia • Sexually (three steps): • Plasmogami (dikaryon) • Karyogami (zygote forms) • Meiosis (sexual spore forms): • Zygospore • Ascospore • Basidiospore

  34. Incompatibility systems Fungi (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.

  35. Chytridiomycota

  36. Zygomycota

  37. Gametangia fuse to produce a zygospore (Rhizopus stolonifer)

  38. Ascomycota

  39. Penicillium and Aspergillus

  40. Examples of conidiophores of other imperfect fungi or Deuteromycetes

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