Bms1026 Fungi

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General

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- eukaryotes, hyphal cell wall made of chitin, have ergosterol in plasma membrane, can contain vacuoles/lipid droplets etc
- SAPROTROPHS: digest dead material /organic material
- can be parasitic or mutalistic
- classified by type of reproduction

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Lifecycle

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- Asexual: mycellum can form spore producing structures (h), which form spores (h) which can then germinate
- Sexual: mycellum fuse in plasmogany (h+h), nuclei then fuse (2h) and produce spore producing structures and spores (h) which then germinate

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Vegetative structures - Filamentous fungi

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- made of long filaments called hyphae, grow to form filamentous mass (mycellium) which can contain cross walls (septa)
- vegetative hyphae obtain nutrients
- arial hyphae have/make reproductive spores
- CYTOPLASMIC STREAMING: unrestricted, bi-directional flow of protoplasm between cells through filaments, spores in septa wall can have plugs to block incase of mechanical damage

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Vegetative structures - Non-filamentous fungi

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- single, round cell (eg yeast)
- can exhibit dismorphism (both filamentous and non filamentous growth)

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Asexual reproduction

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1) hyphal fragmentation: hyphae break into pieces, and each piece can grow into individual hyphae
2) production of spores: formed by mitosis at tips of hyphae, can come in many forms eg conida, dust spores, sporangiospores inside sporangium which burst
3) budding: uneven cell division, a protrusion on cell surface causes nucleus to split and move into bud, cell wall material laid down between developing cell and bud breaks off.

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How fungi get nutrients

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- heterotrophs: they do not make their own food but use preformed sources of organic carbon
- decomposes: saprotrophs can digest most organic compounds to store glycogen (release enzymes from tip which break down subunits which can then be absorbed)

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Adaptions

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- can survive at low pH
- under osmotic pressure (salt/sugar environment)
- in low water activity
- use less nitrogen and can metabolise substrate bacteria ant break down

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Phyla - Chytridiomycota

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- live in water and soil
- zoospores (have flagella)
- mostly plant parasites/saphprocyte (can cause death in frogs by thickening the skin and preventing absorption)

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Phyla - Zygomycota

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- live in terrestrial habitats as saprotrophs
- are coenocytic (septa only found in reproductive structures)
- sexual reproduction = zygospores
- asexual reproduction = sporangiospores

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Phyla - Ascomycota

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- plant pathogen
- morphologically diverse
- sexual reproduction = ascospores
- asexual reproduction = conidia

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Phyla - Basidiomycota

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- mainly saprotrophs (decomposers)
- some plant pathogens
- long lived fruity body (mushroom)
- rare asexual reproduction

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Fungal infections - Plants

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- can cause significant crop loss eg the potato famine in ireland

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Fungal infections - Animals

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1) superficial infections: infection of outer skin layers, nails etc
2) subcutaneous fungal infections: common in tropical/subtropical regions, occur in deep layers of skin, need local surgery/antibiotic treatment
3) systemic mycoses: occurs via inhalation of spores by those with weakened immune systems (OPPORTUNISTIC INFECTIONS) common in immunosuppressed individuals

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Symbiotic actions - Lichens

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- made of fungi and cyanobacteria, act as air quality control

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Symbiotic actions - Mycorrihizae

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- fungi coat roots of plant and act as extension of root for gaining nutrients
- ectomycorrhiza: between root cells
- arbuscular mycorrhiza: invades root cells