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36 Cards in this Set
- Front
- Back
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Define mycology, mycologist, mycotoxicology and mycoses |
Mycology - study of fungi Mycologists - scientists who study fungi Mycotoxicology - the study of fungal toxins Mycoses - diseases caused by fungi |
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Classification of fungi |
Eukaryotes Closely related to animals Unique organisms that differ from animals and plants in nutritional mode, growth and reproduction |
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The distribution of fungi |
Polar to tropics, mainly terrestrial (can be freshwater or marine) Fungal lichen can colonise bare rock faces and allow for ecosytem development. Lichens are associations of fungi with photosynthetic partner e.g. algae (partner supplies food and fungus provides protection e.g. hyphae) Strong and resilient |
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Define heterotroph and osmotroph |
Heterotroph - organism that requires organic substrates to get its carbon for growth and development Osmotroph -absorb their nutrients through cell wall |
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Nutrition of fungi |
They are osmotrophs Digest food outside body by secreting hydrolytic enzymes e.g. cellulases into food so are important biodegraders of ligning and cellulose Saprophytes (live on dead or decaying matter) parasites of mutalists (lichen) Usually aerobes but some yeasts are facultative anaerobes/ obligate anaerobes |
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Structure of fungi |
Fungal body: thallus Range of sizes but larger than bacteria Yeasts are 40microns but mushrooms are visible with naked eye |
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Structure of the fungal cell wall |
Composed mainly of chitin (nitrogen containing acetyl glucosamine polysaccharide), but also glucans, manno proteins and lipids Chitin is strong so makes fungi resilient |
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Function of fungal cell wall |
Structural barrier Protects against osmotic lysis Protects against UV damage Molecular sieve Contains associated enzymes |
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Yeasts |
Unicellular fungus with single nucleus, nuclear envelope, mitochondria and Golgi apparatus Reproduction by budding (asexual) or spore formation (sexual) Egg shaped - not bacteria so can't say if gram positive or negative 3um across so larger than bacteria No flagella |
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Define budding and Binary fission |
Budding - new daughter cell forms off of parent cell, when it becomes same size as parent sell the septum forms and cytokinesis means cells divide Binary fission - where cell divides equally in two |
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Structure of moulds |
Long branched filaments called hyphae 2-30um in diameter Growth occurs at tips Lots of the hyphae intertwine to form mycellium that extend from tip |
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Function of moulds |
Septa (hyphal fragments divide by cross walls) act as structural support, they limit damage when part of hyphae damaged Septa have pores to aid in cytoplasmic streaming (flow of cytosol to deliver nutrients and and organelles) Aseptate - not portioned by septa Coenocytic - multinucleate cell with multiple nuclear divisions |
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Vesicles in hyphae |
Lots of vesicles in hyphal tip - released to form new cell wall structure Some vesicles contain chitin synthase Spitzenkorper - organising centre for hyphal growth and shape formation. Found in tip and consists of lots of small vesicles. |
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Structures present in fungi |
Nucleus - haploid genome Plasma membrane - chitin, glucan synthase proteins Golgi, ER and vesicles - protein modification and secretion Vacuoles - pH regulation, cellular expansion and contraction |
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Structures present in fungi |
Cytoskeleton - microtubules (transport for membrane bound organelles), microfilaments (cytoplasmic contraction) and intermediate filaments (cellular tensile strength) Secretory system - modification of proteins in Golgi before packing into vesicles |
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Define dimorphic |
Ability to change their form Fungi are dimorphic |
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Dimorphism in fungi |
In response to changes in environment e.g. nutrient or CO2 levels Some change form depending on when they are causing disease or growing saprophytically |
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The fungal reproduction cycle |
Vegetative haploid stage - components can become dikaryotic by cytoplasmic fusion Nuclei fuse to produce diploid zygote - reproduction and growth Meiosis from diploid stage - becomes haploid |
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Asexual reproduction of fungi (mitosis) |
Normal vegetative growth occurs by mitosis Asexual reproduction by hyphal fragmentaton, end parts broken off and dispersed or sporulation (spores released into environment and produce new organism) |
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Sexual reproduction Define plasmogamy, dikaryon and karyogamy |
For variation in genome (recombination and genetic exchange) Plasmogamy - fusion of cytoplasm of two haploid compatible fungi (nuclei of two strains present in same cell) Dikaryon - fused hyphae as a result of plasmogamy but no nuclear fusion Karyogamy - fusion of haploid nuclei to produce diploid zygote, meiosis to yield spores |
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The 8 subdivisions of fungi |
Chytridiomycetes Zygomycota Ascomycota Basidiomycota Urediniomycetes Ustilaginomycetes Glomeromycota Microsporidia |
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Chytridiomycetes |
Simplest of fungi - unicellular, produce zoospores (asexual and disperse in environment) with single flagella Symbiotic (mutalistic as provide benefits to host), saprophytic and parasitic Degrade cellulose and keratin Parasites of aquatic plants and animals Asexual and sexual reproduction |
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Asexual reproduction in chytridiomycete |
Mitosis to produce multinucleate cell - zoospore can be produced inside zoosporangian which can lyse and release spores. Fusion of compatible zoospores produces diploid zygote Haploid form restored by meiosis which undergoes vegetative asexual reproduction |
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Zygomycota |
Form coenocytic hyphae (without septa) with many haploid nuclei Saprophytic or animal/plant parasites Used to produce fermentative soy products, antiseptics, food colouring Hyphae from different strains fuse to produce progametangi and form zygot. Zygospores undergoes meiosis to release spore |
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Ascomycota |
Degrade stable organic compounds e.g. lignin, cellulose and collagen e.g. Baker's and Brewer's yeast, truffles, Candida (thrus), Dutch elm disease Sexual reproduction - ascomycetes produce ascus containing haploid ascospores which are released in environment for dispersal |
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Yeast replication |
Asexual reproduction - BUDDING. Daughter cells undergoes septation and cytokinesis to produce two daughter cells. Diploid undergoes meiosis to produce ascus (sac which spores develop in). Meiosis occurs in nutrient poor conditions Haploid ascospores undergo asexual reproduction through vegetative life cycle. |
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Filamentous ascomycete replication |
Ascogoneium forms giving rise to dikaryotic ascogenous hyphae. Karyogamy occurs and zygote formed - undergoes meisosis and mitosis to give rise to 8 ascospores in ascus which are released into environment |
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Basidiomycota |
Sexual reproduction - form basidia e.g. mushroom. Dikaryotic mycellium develops in mushroom, nuclei fuse to form diploid nucleus. Undergo meiosis to produce 4 haploid nuclei and eventually basidospores. Basidospores released from basidium into environment |
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Urediniomycetes and Ustilaginomycetes |
Considered Basidomycetes but can be separated genetically Plant pathogens that cause rusts (uredinomycetes) and smuts (ustaliagomycetes) Rusts are obligate biotrophic parasites, have to cause disease to survive Ustilago maydis - tumour development in corn kernels, give nutrients to infective fungus |
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Glomeromycota |
Asexual reproduction only Form intracellular associations within roots of herb plants and tropical trees Colonise plants roots, increase absorption capacity and protect roots (by wrapping hyphae around to increase SA for absorbing nutrients from soil). Fungus gets carbon source, fungi help with nutrient absorption |
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Mycorrhizal fungi |
Arbuscular myorrhizae - 85% plant families e.g. Glomeromycota Ectomycorrhizae - 10% plant families e.g. hyphal sheath, ascomycetes, basidomycetes and zygomycetes |
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Microsporidia |
Considered protists Obligate intracellular parasites that infect insects, fish and humans (diarrhoea, pneumonia and encephalitis) Lack important cellular organelles e.g. no mitochondria have unique morphology Puncture infection - cannot get in without puncture wound |
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Uses of fungi |
Food and beverages - mushrooms, soy products, bread, beer, alcohol, blue cheese Environmental - biodegraders of organic molecules, nutrient cycling Medical - antibiotics, statins, cyclosporin (immune supression) Agricultural - biopesticides, certain plants Industrial - bioremdiation, biofuels Research |
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Detrimental impact of fungi |
Major cause of plant disease in agriculture e.g. rusts and smuts. Produce hydrolytic enzymes that damage plant cell wall e.g. cellulase and pectinases Only about 200-300 fungi that cause disease in humans, but increasing incidence due to immuno compromised population |
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4 divisions of fungal disease |
Superficial mycoses - don't penetrate skin Cutaneous and subcatenous mycoses - infection of skin and hair Systemic mycoses - penetrate deeper so cause more problem Opportunistic mycoses - infect all organs as fungus spreads throughout body |
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Fungal diseases in mammals |
Ringworm Athletes foot |
