Eukaryotes have cell membranes and nuclei



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tarix25.05.2018
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Eukaryotes have cell membranes and nuclei

  • 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


  • bacteria

  • actinomycetes



Tiny (1 μm width), one-celled

    • 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

    • zone surrounding root
      • dead root cells and exudate stimulate microbial growth








1. Decomposers

  • 1. Decomposers

  • Organic chemicals in big complex chains and rings

    • Bacteria break bonds using enzymes they produce
      • Create simpler, smaller chains
  • Immobilize nutrients in their cells; prevents loss of nutrients from rooting zone

  • 2. Mutualists

  • form partnerships with plants (e.g. Rhizobium and legumes)

  • 3. Pathogens

  • cause plant galls

  • 4. Chemoautotrophs get energy from compounds other than compounds







Make “earthy” smell

  • Make “earthy” smell

    • by producing geosmin
  • adaptable to drought

  • Can act in high pH

  • usually aerobic heterotrophs

  • break down “recalcitrant” compounds

    • Hard-to-decompose (chitin, cellulose)
  • Produce antibiotics, like Streptomycin





  • Protozoa

  • Algae

  • Fungi





Unicellular; larger than bacteria

  • Unicellular; larger than bacteria

  • Amoeba, ciliates, flagellates

  • Heterotrophic

    • Eat bacteria
    • Bacteria have more nitrogen than protozoa need, so protozoa release the excess
    • mineralize
  • Form symbiotic relationships

  • e.g., flagellates in termite guts; digest fibers

  • Require water

    • Go dormant within cyst in dry conditions




Filamentous, colonial, unicellular

  • 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




Grow as long threads (hyphae)

  • Grow as long threads (hyphae)

    • Push through soil particles, roots, rocks
  • Often group into masses called mycelium (look like roots)

  • Higher fungi have basidium :

  • club-shaped structure ,

  • bearing fruiting body







Break down OM, esp important where bacteria are less active; low pH

  • Break down OM, esp important where bacteria are less active; low pH

  • attack any organic residue

      • feed by absorbing nutrients from organic material ; no stomachs;d igest food before it can pass through the cell wall into the hyphae.
        • Hyphae secrete acids and enzymes that break the surrounding organic material down into simple molecules they can easily absorb.
  • Most are aerobic heterotrophs

  • chemosynthetic: adsorb dissolved nutrients for energy







Like bacteria: immobilize nutrients in soil

  • Like bacteria: immobilize nutrients in soil

  • Produce organic acids; increases humic-acid-rich OM that is resistant to degradation

    • Lasts in soil for 100s of years




Mycorrhizae: symbiotic absorbing organisms infecting plant roots, formed by some fungi

  • Mycorrhizae: symbiotic absorbing organisms infecting plant roots, formed by some fungi

      • Mutualists
        • Get carbon from plant
        • Give to plant:
          • Solubilize P; bring soil nutrients to plant
    • 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




Grow on surface layers of roots

  • Grow on surface layers of roots

    • trees




Grow within root cells

  • Grow within root cells

    • Grasses, crops, vegetables, shrubs




(Macrofauna: > 1 cm long)

  • (Macrofauna: > 1 cm long)

  • ANNELIDS

  • several types:

  • epigeic (litter)

  • anecic (burrow)

  • endogeic (in soil)





  • CHORDATES (vertebrates)

  • mammals, amphibians, reptiles

  • PLATYHELMINTHES (flatworms)

  • ASCHELMINTHES (roundworms, nematodes)

  • MOLLUSKS (snails, slugs)

  • ARTHROPODS : (insects, crustaceans, arachnids, myriapoda)



Squirrels, mice, groundhogs, rabbits, chipmunks, voles, moles, prairie dogs, gophers, snakes, lizards, etc.

  • Squirrels, mice, groundhogs, rabbits, chipmunks, voles, moles, prairie dogs, gophers, snakes, lizards, etc.

  • Contribute dung and carcasses

  • Taxicabs for microbes





Nonsegmented, blind roundworms

  • Nonsegmented, blind roundworms

  • > 20,000 species

  • Eat bacteria or fungi or plants (stylet)

    • And protozoa, other nematodes, algae
  • Specialized mouthparts

    • Can sense temperature and chemical changes


nematode

  • nematode





¾ of all living organisms

  • ¾ of all living organisms

  • Exoskeleton, jointed legs, segmented body

  • Insects

  • Crustaceans

  • Arachnids

  • Myriapoda



Shredders

  • Shredders

  • Microbial taxis



  • Mini-movie



  • Mini-movie



Feeding Habits

  • Feeding Habits

  • Carnivores : parasites and predators

  • Phytophages: eat above ground green plant parts, roots, woody parts

  • Saprophages: eat dead and decaying OM

  • Microphytic feeders: eat spores, hyphae, lichens, algae, bacteria



Distribution with depth

  • Distribution with depth

  • most active biotic horizons correspond with amount of OM:

  • Roots:

    • Rhizosphere: zone surrounding root
      • dead root cells and exudate stimulates microbial growth
        • Most microbiotic population in A and rhizosphere


ACTIVE fraction:

  • ACTIVE fraction:

    • Organic compounds that can be used as food by microorganisms
  • LABILE:

    • OM that’s easily decomposed


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