Presentation on theme: "Filamentous fungi - a background Lecture 1 and 2 What are they? What are they doing?"— Presentation transcript:
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
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.
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
Medicines that come from fungi Penicillin. Penicillium chrysogenum. Alexander Fleming, 1928. Cephalosporin Cyclosporin
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.
Smut infection of a wheat field in Eastern Washington (1956)
Examples of symptoms caused by fungi: Cankers Storage rots of fruits and vegetables Rust, mildews Leaf spots
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.
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.
Botrytis cinerea causes rots on fruits and vegetables, blossom blights, damping off, stem cankers, leaf spots and bulb rots. scleriotia
In the field, blossom blight often precede the fruit rots The fungus enters the fruit through the dead flower petals.
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.
Spots on fruits are from spores that have landed Attack on fruit originated in the flower
Grey mould - continued B. cinerea overwinters as mycelium in decaying plant debris or as sclerotia - black, hard resting structures.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.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.
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
Incompatibility systems Fungi (ascomycetes) have mating types. They are designated MATa and MAT (yeast), MATA and MAT (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.