Micro - fungal diversity

What are chytrids?

• Made up of three separate phyla of fungi - Chyridiomycotina, Blastocladiomycota and Neocallimastigomycota

• Found in aquatic, marine and moist soil environments

• Mainly saprotrophs, some are obligate biotrophs (pathogens)

• Utilise anaerobic metabolism

What are the key features of a chytrid?

• Contain a main thallus (2-10um in diameter) - zoosporangium

• Filamentous rhizoids extend from the back of the fungus

• Zoosporangia contain zoospores

• Zoospores have a single posterior flagellum - moves via whiplash

• Zoospores are motile and show chemotaxis - encyst and form resting spores when connected to a cell

How is there diversity within the chytrid group?

• Some sporangia have a lid (operculum)

• Chytrids may be monocentric (one sporangium) or polycentric (multiple sporangia)

What is the importance of chytrids?

• Decompose particulate organic matter

• Major degraders of cellulose in the rumen of cattle

• Convert inorganic compounds into organic compounds

• Pathogens of aquatic plants and animals

• Vectors of viral diseases

• Zoospores are a food source of zooplankton

How do the zygomycota reproduce?

• Produce asexual spores in the sporangium

• Sexual spores are known as zygospores

• Contain melanin and sporopollenin and are very long-lived

How do the zygomycota act as pathogens?

• Alter host behaviour by taking over the brain

• Parasites of small animals

• Complex life cycles ensure good spore dispersal

• Numerous species can cause disease in plants and animals - zygomycosis

What are the glomerulomycota?

• Obligate mutualistic biotrophs

• Ecologically/economically the most interesting group of fungi

• Known as arbuscular mycorrhizae or vesicular-arbuscular mycorrhizae

• Multinucleate spores have a 40-800um diameter

• Spores have a layered wall

• Does not undergo a sexual cycle

What are the Ascomycota?

• Largest, most diverse group of fungi

• Majority of lichenised fungi belong to the ascomycota

• Yeasts are polyphyletic with representatives in each subphylum

• Ascomycetes produce septate hyphae

How do the ascomycota store their spores?

• Hymenium-supporting sexual spores (ascospores)

• Spores can be naked or produced in fruitbodies (ascoma, ascomata or ascocarps)

• Typical ascus contains eight ascospores

How do the ascomycetes reproduce asexually?

• Spores are produced by conidiation

• Spores are known as conidia

What are the basidiomycota?

• Phylum containing most of the macrofungi (mushrooms) and some basidiomycetous yeasts

How do the basidiomycota produce and distribute their spores?

• Basidiospores are produced on basidia

• Basidia are simple structures in the homobasidiomycetes

• Spore discharge is passive or mediated by Buller’s drop

• Basidia in the heterobasidiomycetes are complex