Micro 15

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  1. What is an ecosystem?
    The sum of all organisms and abiotic factors in a particular environment. An ecysystem is a dynamic complex of plant, animal and microbial communities and the nonliving surroundings, which interact as a functional unit
  2. What is a habitat?
    Portion of an ecosystem where a commjnity could reside. Many habitats are unsuitable for plants and animals and some habitats are almost exclusively
  3. What is a population?
    Group of microorganism of the same sepcies residing in the same pace at the same time
  4. What is a community?
    A group of a population
  5. What are the two different ways in which diversity of a microbial species in an ecosystem can be expressed?
    • Species richness
    • Species abundance
  6. What does species richness refer to?
    The total number of different species present
  7. What does species abundance refer to?
    The propertion of each species in an ecosystem
  8. What are microbial species richness and abundance a function of?
    Microbial species richness and abundance is a function of the kinds and amounts of nutrients available in a give habitat
  9. What are guilds?
    Metabolically related microbial populations. Sets of guilds form microbial communities that interact with macroorganisms and abiotic factors in the ecosystem
  10. What is a niche?
    Habitat share by a guild. Supplies nutrients as well as conditions for growth
  11. What does the growth of microbes depend on?
    The growth of microbes depends on resources and growth conditions
  12. What is a microenvironment?
    • The immediate environmental surroundings of a microbial cell or group of cells
    • Soil particles contain many microenvironments
  13. Describe the physiochemical conditions in microenvironments
    Physiochemical conditions in a microenvironment are sunject to rapid change, both spatially and temporally
  14. What is parasitism?
    One member in the relationship is harmed and the other benefits
  15. What is mutualism?
    Both species benefit (symbiosis)
  16. What is commensalism?
    One species benefits and the other is neither harmed nor helped
  17. What is biogeochemistry?
    The study of biological mediatd chemical transformations
  18. What is a biogeochemical cycle?
    A biogeochemical cycle defines the transformations of a key element by biological and chemical agents
  19. What are the major end products of the carbon cycle?
    CH4 and CO2
  20. What organisms are the foundation of the carbon cycle?
    Phototrophic organisms
  21. What is the most stable form of nitrogen?
  22. What is denitrification?
    The reduction of nitrate into gaseous nitrogen products and is the primary mechanism by whith H2 is produced biologically
  23. What is the most abundant organic slfur compound in nature?
    • Dimethyl sulfide
    • Produced primarily in marine environments as a degradation product of dimethylsulfoniopropionate
    • DMS can be transformed via a number of microbial processes
  24. What is soil?
    The loose outer material of Earth's surface, distinct from bedrock
  25. What are the two broad groups soil can be divided into?
    • Mineral soils
    • Organic soils
  26. What are mineral soils?
    Derived from rock weathering and otther inorganic materials
  27. What is organic soils?
    Deried from sedimentation in bogs and marshes
  28. What are soils composed of?
    • Inorganic mineral matter (~40% of soil volume)
    • Organic matter (~5%)
    • Air and Water (~50%)
    • Living organisms
  29. What is the O horizon of soil?
    Layer of undecomposed plant materials
  30. What is the A horizon of soil?
    Surface soil (high in organic matter, dark in color, is tilled for agriculture; plants and large numbers of microorganisms grow here; microbial activity high)
  31. What is the B horizon of soil?
    Subsoil (minerals, humus and so on, leached from soil surface accumulate here; little organic matter; microbial activity detectable but lower than at A horizon)
  32. What is the C horizon of soil?
    Soil base (develops directly from underlying bedrock; microbial activity generally very low)
  33. What is the most important factor in subsurface environments?
    Nutrient availability
  34. Where does most microbial growth take place in soil?
    On the surface of soil particles
  35. What is the most important factor influencing microbial activity in soil?
    Water availability
  36. What happens to water in sand?
    It drains quickly
  37. What happens to water in silt?
    Retains water to the right extent
  38. What happens to water in clay?
    Water retained too well, soil becomes anoxic
  39. What are prokaryotes largely responsible for in soil?
    • The production of humus
    • Release of minerals from soil particle (Production of acids from organic compounds solubilize the minerals)
    • Cycling of nutrients
    • Nitrogen fixation
  40. What is the rhizosphere?
    Soil that surrounds plant roots and recieve plant secretions
  41. What is a mycorrhizae?
    Association of fungi with plant roots?
  42. What is nitrogen fixation catalyzed by?
    nitrogenase complex (metal cofactors)
  43. What is the final product of nitrogen fixation?
    Ammonia, ued to produce amino acids
  44. What are some examples of free-living nitrogen fixers?
    Azotobacter, Beijerinckia, Clostridium
  45. Where are free-living nitrogen fixers found?
    Widespread in soil, require a soil rich in organic matter to provide energy for nitrogen fixation
  46. What is Clostridium?
    Strict anaerobe
  47. What is Azotobacter?
    Strict anaerobes. The enzyme is protected by very high rate of O2 consumption, which keeps the intracellular environment anaerobic
  48. What is cyanobacteria?
    Only some species are capable of N2 fization. MAJOR nitrogen-fixing organism in nature. Cyanobacteria produce energy by oxygenic photosynthesis, oxygen is produced in the cell
  49. Where does nitrogen fixation occur within cyanobacteria?
    Nitrogen fixation occurs in specialized anaerobic cells (heterocysts), which lact PTSII, and produce ATP by cyclic photophosphorylation
  50. What is special about hetercysts?
    They have thick cell walls that slow the diffusion of O2
  51. What is symbiotic nitrogen fixers?
    The mutulastic relationship between legumious pabts and nitrogen-fixing bacteria is one of the most important symbioses known
  52. What are the steps of nodule formation?
    • Step 1: recognition and attachment of bacterium to root hairs
    • Step 2: excretion of nod factors by the bacterium
    • Step 3: bacterial invasion of the root hair
    • Step 4: Travel to the main root via the infection thread (tube composed of cellulose)
    • Step 5: Formation of bacteroid state within plant cells (swollen and misshapen bacteria-fix N2)
    • Step 6: Continued plant and bacterial division, forming the mature root nodule
  53. How are O2 levels in nodules controlled?
    O2 levels are controlled by the O2-binding protein leghemoglobin, produce by the plant cells
  54. What happens if soil is poorly drained?
    • If the soil is poorly drained and becomes waterlogged conditions becomes anaerobic, which promotes denitrification
    • Anaerobic conditions also promotes sulfur and sulfate reduction which produce H2S (toxic for plants)
Card Set:
Micro 15
2012-03-21 01:57:37
Micro 15M

Micro 15
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