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Fungi Overview of fungi Biology of fungi
True multicellularity with differentiation Strict heterotrophs Release enzymes into environment- digestion is extracellular Most are saprophytic Along with bacteria, fungi are important as decomposers Biology of fungi Body - mass of filaments called a mycelium Each filament is a hypha- increase surface area for absorption Some have crosswalls between cells-septa Nonseptate fungi lack crosswalls between cells-multinucleate
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Fungal mycelia and hyphae
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Fungi cont’d. Fungal cell structure Cell walls contain chitin
Polymer of glucose Each glucose has an amino group attached Found in exoskeletons of animals Energy reserve is glycogen like animal cells Move toward food source by growing toward it Hyphae can grow as much as a meter per day!
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Fungi cont’d. Fungal reproduction
Adapted to dry land - produce wind-blown spores Haploid reproductive cell - germinates and develops into new mycelium-asexual Sexual reproduction - conjugation of two different mating types Designated as + and – Dikaryonic state - in some, the + and – nuclei do not fuse for long periods of time After fusion of nuclei, a zygote forms - undergoes meiosis Produces haploid spores and cycle begins again
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Dispersal of spores Fig
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Bird’s Nest Mushroom
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Fungi cont’d. Diversity of Fungi
- classified by mode of sexual reproduction 1. Zygospore fungi - Phylum Zygomycota Saprotrophs and parasites Rhizopus stolonifer – black bread mold is a familiar zygospore fungus life cycle is illustrated on following slide Note formation of a zygospore from fusion of + and - hyphae
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Black bread mold Rhizopus stolonifer
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Fungi cont’d. 2. Sac fungi - Phylum Ascomycota
Sexual reproductive structure called an ascus Asci are enclosed within an ascocarp Ascocarp develops after fusion of + and – hyphae Union of + and – nuclei produces and ascus Ascus produces spores by meiosis In asexual reproduction, the asexual spores are called conidia Unicellular ascomycetes are often called yeasts Unequal binary fission- called budding Fermentation by some yeasts produces CO2 and ethanol Used to make beer, wine, and bread
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Sexual reproduction in sac fungi
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Asexual reproduction in sac fungi
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Fungi cont’d. 3. Club fungi- Phylum Basidiomycota
Characteristic sexual reproductive structure is called a basidium Contained within a basidiocarp Edible part of a mushroom is the basidiocarp Forms after fusion of + and – hyphae Sexual reproduction is most prominent in this group Asexual reproduction can occur by asexual spores called conidia
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Sexual reproduction in club fungi
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Fungi cont’d. 4. Imperfect fungi - Phylum Deuteromycota
Includes many familiar fungi Aspergillis- used to make soy sauce from fermenting soy beans Penicillium- original source of penicillin Penicillium roquefortii and camemberti- used in making blue cheeses Deuteromycetes always reproduce asexually Produce conidia on aerial hyphae Sexual stage has not been identified and may not exist
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Blue cheese Fig
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Fungi cont’d. Environmental importance of fungi
Fungi and photosynthesizers Lichens- associations between fungi and cyanobacteria or green algae Efficient at acquiring nutrients and moisture-can colonize poor soil, rocky surfaces Produce organic matter and create new soil 3 characteristic forms- crustose, foliose, fruticose Body of lichen has 3 layers-fungi form top and bottom layers and protect middle layer of photosynthetic cells Protects photosynthesizer and delivers water Photosynthesized gives the fungus nutrients
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Lichen morphology Fig
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Fungi cont’d. Environmental aspects, cont’d. Mycorrhizal fungi
Mutualistic relationships with plant roots Helps plants to grow more successfully in poor soils Fungi can live on the outside surface of roots, or it can penetrate the root tissues Plant provides organic nutrients to the fungus Fungus brings water and minerals to the plant Hyphae provide lots of surface area for water absorption
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Fungi cont’d. Medical aspects of fungi Fungal diseases of plants
Many enter through the stomata of the leaves or through a wound Smuts and rusts- sac fungi that parasitize cereal crops Fungal diseases of humans Mycoses Cutaneous- affect only the skin Subcutaneous-deeper skin layers Systemic-spread throughout the body Many fungal diseases are acquired from the environment Ringworm from soil fungi for example
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Smuts and rusts Fig
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Fungi cont’d. Human fungal diseases Tineas Histoplasmosis Candidiasis
Skin infections-can occur anywhere on the skin Athlete’s foot- scaling, peeling, and itching between toes Ringworm- redness and inflammation due to enzymes released by the fungus; extends outward in a ring-shape Histoplasmosis Caused by Histoplasmosis capsulatum; common in the Midwest Carried in bird droppings Mild flu-like symptoms, fungus lives in cells of the immune system Healed lesions in the lungs calcify Candidiasis Yeast infections resulting from imbalance of normal flora
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Human diseases caused by fungi
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Fungi cont’d. Control of fungi
Fungi more closely resemble animal cells than bacteria Makes it harder to develop antibiotics that will kill fungi and not the host Fungi synthesize steroids differently-fungicides are directed at steroid biosynthesis
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