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Soil ORGANISMS

Discover the kingdoms of life in soil and the vital role of eukaryotes, bacteria, fungi, protozoa, and archaea. Learn about their functions, importance in soil health, and unique adaptations.

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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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