fungi
DESCRIPTION
Fungi. Overview 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 - PowerPoint PPT PresentationTRANSCRIPT
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Fungi
• Overview 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
• Fig. 28.23
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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!
https://www.youtube.com/watch?v=EDkR2HIlEbc
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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. 28.24
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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
• Fig. 28.25
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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
• Fig. 28.26
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Asexual reproduction in sac fungi
• Fig. 28.27
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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
• Fig. 28.28
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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. 28.29
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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. 28.30
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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. 28.31
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Fungi cont’d.
• Human fungal diseases– Tineas
• 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
• Fig. 28.32
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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