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Filamentous fungi - a background

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Presentation on theme: "Filamentous fungi - a background"— Presentation transcript:

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


4 Fly agaric (flugsvamp)

5 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.

6 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

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

8 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.

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

10 Ustilago maydis - the corn smut fungus

11 Ustilago maydis is a popular food delicacy in Mexico


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

14 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.

15 Botrytis cinerea - a fungus -causes grey mold

16 Grey mould of strawberries

17 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.

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

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

20 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.

21 Botrytis cinerea of tomato

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

23 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.

24 Life cycle of Botrytis cinerea

25 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

26 Powdery mildew on Poinsettia

27 Powdery mildew on squash

28 Powdery mildew on cucumber

29 Life cycle of powdery mildew

30 Rust of roen (rönn)

31 Rust of raspberry

32 Rust of rose

33 Four phyla of fungi Chytridiomycota - no sexual spore
Zygomycota - zygospore Ascomycota - ascospore Basidiomycota - basidiospore

34 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.

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

36 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.

37 Chytridiomycota

38 Zygomycota

39 Gametangia fuse to produce a zygospore (Rhizopus stolonifer)

40 Ascomycota


42 Penicillium and Aspergillus

43 Examples of conidiophores of other imperfect fungi or Deuteromycetes

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