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Soil ORGANISMS

Soil ORGANISMS. Global Soil Biodiversity Initiative. website. KINGDOMS OF LIFE. Eukaryotes have cell membranes and nuclei All species of large complex organisms are eukaryotes, including animals , plants and fungi , although most species of eukaryotic protists are microorganisms .

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Soil ORGANISMS

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  1. Soil ORGANISMS

  2. Global Soil Biodiversity Initiative • website

  3. KINGDOMS OF LIFE

  4. Eukaryotes have cell membranes and nuclei • All species of large complex organisms are eukaryotes, including animals, plants and fungi, although most species of eukaryotic protists are microorganisms. • Prokaryotes lack nucleus • bacteria

  5. Organic portion composed of: 5% 10% 85% Humus & decomposing organic litter

  6. Living organisms <5% Fresh residue <10% Stabilized organic matter (humus) 33% - 50% Decomposing organic matter (active fraction) 33% - 50%

  7. The divisions of the 5%: 40% bacteria and actinomycetes

  8. BACTERIA

  9. Bacterial biomass dominates : • grassland and agricultural landscapes Fungal biomass dominates: Forests

  10. bacteria

  11. Bacteria • Tiny (1 μm width), one-celled • Single cell division • In lab: 1 can produce 5 billion in 12 hours • (In real world limited by predators, water & food availability) • Abundant in rhizosphere • Four FUNCTIONAL GROUPS: • Decomposers • Mutualists : partner with plants • Pathogens • Chemoautotrophs

  12. Some terms: • Autotrophs: can make organic compounds from inorganic compounds • Heterotrophs: feed on others to make organic compounds • Chemosynthetic: get energy from inorganic chemical reactions • Photosynthetic: get energy from sun • Aerobes: use aerobic respiration (need oxygen as electron acceptor) • Anaerobes: use inorganic or organic compounds for electron acceptor

  13. Decomposers • Organic chemicals in big complex chains and rings • Bacteria break bonds using enzymes they produce • Create simpler, smaller chains

  14. Mutualistse.g., Nitrogen-fixing Bacteria • Nodules formed where Rhizobium bacteria infected soybean roots.

  15. Root nodules

  16. Chemoautotrophs • Get energy from OTHER THAN CARBON compounds • From N, S, Fe, H

  17. Actinomycetes • Are bacteria but grow like fungi • Filamentous but morphology varies • Adaptable to drought • Important at high pH • Usually aerobic heterotrophs • Break down wide range of organic compounds • Produce geosmin (smell of “fresh soil”)

  18. 40% other Microflora Protozoa Algae Fungi

  19. PROTOZOA

  20. Protozoa Flagellates Amoeba Ciliates Eat bacteria & protozoa

  21. protozoa • Unicellular • Heterotrophic • Eat bacteria, fungi Form symbiotic relationships e.g., flagellates in termite guts; digest fibers • Require water • Go dormant within cyst in dry conditions

  22. Function of protozoa • Make nutrients plant-available • Release excess N from the bacteria they eat • Regulate bacteria populations • Compete with pathogens

  23. PROTOZOA bacteria Sand protozoa

  24. Flagellate

  25. Ciliate

  26. Amoeba bacteria amoeba

  27. Soil-Dwelling “Vampires” • Group of amoebe that drill holes in fungus and consume liquid Vampyrellids

  28. Archaea ( ar-KEY-ah) • A recent discovery: 1970s • Woese and Fox: • Divided bacteria into “normal” and “extremophiles” (archaeabacteria) • Changed classic “tree of life” Eukaryotes Archaea Bacteria

  29. Very similar to bacteria in shapes and size and reproduction • Differences: • Cell membranes contain lipids • Not chitin (like fungi) • Not cellulose (like plants) • Genes of archaea are more similar to eukaryotes than to bacteria • Can use a lot of various substances for energy

  30. Importance • Role in carbon cycle • Photoautotrophs, chemoautotrophs, photoheterotrophs, chemoheterotrophs • Many can survive in extreme environments (enzymes); heat, cold, salt, low pH • Many are methane-producers: • Swamp gas, cow farts • Sheer numbers: • Combined marine and soil archaea make them the most abundant organism on earth

  31. Importance in Soil • Role in N cycle • Ammonia oxidizers • Decomposition • Important anaerobic decomposers • Important in extreme environments where bacteria do not fluorish

  32. algae • Filamentous, colonial, unicellular • Photosynthetic • Most in blue-green group, but also yellow-green, diatoms, green algae • Need diffuse light in surface horizons; important in early stages of succession • Form carbonic acid (weathering) • Add OM to soil; bind particles • Aeration • Some fix nitrogen

  33. Fungi • Break down OM, esp important where bacteria are less active • attack any organic residue • Most are aerobic heterotrophs • chemosynthetic: adsorb dissolved nutrients for energy

  34. Grow from spores into branched hyphae • Hyphal strand divided into cells by septa that allow flow of liquids between cells Masses of hyphae grow together in visible threads called mycelia

  35. Advantages over bacteria: • They can grow in length • Rate: 40 μm / min (bacterium travels 6 μm in its life) • Don’t need a film of water to move • Can find new food sources • Transport nutrients great distances • Produce enzymes that break down complex compounds • Can break down lignin (woody compound that binds cellulose), shells of insects, bones • Can break down hard surfaces

  36. Clever, clever adaptations! • Infecting a nematode • Hypha twists back on itself and catches a nematode, hyphal cells swell and kill nematode then enter body and suck out nutrients • Oyster mushroom • Emits toxic drops from hyphal tips which touch nematode, immobilize it and hyphae enter body and remove nutrients • Trap arthropods or protozoa and digest them

  37. Mycorrhizae: symbiotic absorbing organisms infecting plant roots, formed by some fungi • normal feature of root systems, esp. trees • increase nutrient availability in return for energy supply • plants native to an area have well-developed relationship with mycorrhizal fungi • Can extend the effective surface area of tree’s roots by 700-1000 x

  38. Mycorrhizae Tree root Fungal hyphae Mycorrhizal structure

  39. Ectomycorrhizal Endomycorrhizal • Grow close to root surfaces • Hardwoods and conifers • Penetrate and grow inside roots • Vegetables, annuals, grasses, shrubs, perennials, softwoods

  40. Ectomycorrhizae

  41. Arbuscular Mycorrhizae (AM)

  42. Higher fungi have basidium : club-shaped structure , bearing fruiting body • toadstools, mushrooms, puffballs, bracket fungi

  43. Fungi and Soil Quality • Decompose carbon compounds • Improve OM accumulation • Retain nutrients in the soil • Bind soil particles • Food for the rest of the food web • Mycorrhizal fungi • Compete with plant pathogens

  44. 12% Earthworms (Macrofauna: > 1 cm long) ANNELIDS

  45. earthworms • Some 7000 species • 3 categories: • Epigeic (leaf litter/compost dwelling ) • Endogeic (topsoil or subsoil dwelling ) • Anecic (deep burrow drillers)

  46. Giant • Benefits to soil • Move air in and out of soil • Castings are rich in available nutrients • Produce 10 lbs / yr

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