1 / 14

Fungi 1 Importance; Structure & Growth

Fungi 1 Importance; Structure & Growth. Fungi. Definition Eucaryotic, spore-gearing organisms with absorptive nutrition, no chlorophyll, and that reproduce sexually and asexually. Includes Kingdom Fungi Lower fungi Higher fungi. Kingdom Protista Slime molds (cellular and acellular).

orsin
Download Presentation

Fungi 1 Importance; Structure & Growth

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Fungi 1 Importance; Structure & Growth

  2. Fungi Definition Eucaryotic, spore-gearing organisms with absorptive nutrition, no chlorophyll, and that reproduce sexually and asexually. • Includes • Kingdom Fungi • Lower fungi • Higher fungi • Kingdom Protista • Slime molds (cellular and acellular) Species 90,000 sp. described; 1.5 million spp. estimated to exist (Prescott et al., 1999).

  3. Fungi • Chemoorganotrophs • Organic compounds as sources of carbon, electrons and energy. • Most use carbohydrates and nitrogenous compounds to synthesize their own amino acids and proteins. • Aerobes • Usually aerobic; • Some facultative anaerobes e.g. yeasts in alcoholic fermentation. • Obligate anaerobes found in ruminants. • Most are saprophytes • Extracellular hydrolytic enzymes; hydrolysis; absorption of hydrolyzed products.

  4. Importance in the biosphere Saprophytism • Primary colonizers of plant litterMost fungal species can feed on complex polymers • PolymersLong chain, branched and aromatic organic molecules such as cellulose, pectin, lignin by basidiomycetes and ascomycetes. • Small organic moleculesSugars; fats; peptides by lower fungi and slime molds.

  5. Importance in the biosphere Symbiosis • Mycorrhiza (fungus/root) e.g. wheat/Glomus sp.; pine/Leucopaxillus sp.May/may not be obligateMay (endo-)/may not (ecto-) enter the hostFungus receives plant photosynthatePlant receives mineral nutrients and protection from pathogens • Lichens (alga/fungus)Sugars; fats; peptides by lower fungi and slime molds.

  6. Importance in the biosphere Parasitism and predation • Plants 8,000 spp. of fungi cause diseasee.g. rusts and take all in wheat; potato blight • Animals 50 spp. of mostly opportunistic yeasts. • Systemic mycoses of internal organs e.g.Candida albicans candiasis of the intestinal thrush. • Superficial mycoses e.g.Trichophyton spp. which cause ringworm and athelete’s foot. Nematode-trapping fungi.

  7. Importance in the biosphere Mycotoxins Secondary metabolites highly toxic to animals (ppm concentrations) Examples • Aflatoxin from Aspergillus flavusA. flavus grows in maize and cereals under warm, moist storage; and in peanut pods underground before harvest. Causes aflatoxicosis. • Amanitin from Amanita muscariaToadstools (hallucinations; liver damage; death). • Ergot alkaloids from Claviceps purpureaErgotism from ingestion of infected seedheads of rye and grasses.

  8. Importance in the biosphere Industrial, food and agricultural uses • Chemicals e.g. antibiotics; organic acids. • Biomass e.g. mushroom; mycoprotein. • Food fermentations e.g. tempe; cheese; alcohol production; bread; soy sauce. • Biocontrol agentse.g. mycoherbicides; mycoinsecticides. Also see lectures on Agricultural Microbiology and Industrial Microbiology

  9. Importance in the biosphere Biodegradation Damage by saprophytes results in economic losses. • Fungi are ubiquitous. • Nutrients for saprophytic growth found in: • Foodstuffs • Building materials • Textiles • Packaging • Control measures based on imposition of unfavorable environment on the fungus e.g. gas/vacuum packaging; chemical inhibitors; asepsis; water activity; temperature control.

  10. Importance in the biosphere Bioremediation Reduction of waste materials by exploiting the biochemical capability of the fungi e.g. • Cellulosic materials e.g. composting • Effluent treatment e.g. biobleaching

  11. Structure • Filamentous • Hyphae • Mycelium (pl. mycelia) • Pseudomycelium (single-cells; no cytoplasmic streaming) • Dimorphism • Yeast form ↔ Mycelial form • YM shift • Septa • Non-septate (coenocytic) • Septate (acoenocytic) • Uni- or multiperforate septa permits cytoplasmic streaming

  12. Growth Filamentous fungi grow by hyphal extension • PropaguleHyphal tips; hyphal fragments; spores • Hypha/hyphaeDaughter cells by central constriction and formation of septa • Mycelium (pl. mycelia) • Colony (thallus) Yeasts grow by budding

  13. Secondary metabolite Primary metabolite Biomass Metabolite Growth • Growth measured in • Colony mass • Colony diameter • To produce growth curves similar to that of the bacteria Metabolic products typically occur at different stages of the growth curve

  14. Growth Fungi can propagate via • Hyphal fragmentaionLysis of aged parts of hyphae; other living sections to grow into new colonies.Mechanical breakage e.g. soil disturbance; break-up of substratum. • Sclerotia Specialized hyphal propagules.Storage and survival structure; resistant to extreme environmental conditions.Germinate to form new hyphae or sexual spores. • RhizomorphsHyphal aggregations growing in parallel into rope-like structures a few cm long and 1 – 2 mm thick.Transports fungus to another part of the substratum e.g. rotting wood, from where hyphae disperse and spread out.

More Related