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LSCI 230: Microbiology > Soil Microbiology > Flashcards

Soil Microbiology Flashcards

1
Q

Ecosystem

A

The sum of all organisms & abiotic factors in a particular environment

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2
Q

Habitat

A

Portion of an ecosystem where a community could reside

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3
Q

Population

A

Group of microorganisms of same species residing in same place at same time

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4
Q

Community

A

A group of populations

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5
Q

Species richness

A

The total number of different species present

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6
Q

Species abundance

A

The proportion of each species in an ecosystem

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7
Q

Guild

A

Metabolically related microbial populations

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8
Q

Niche

A

Habitat shared by a guild

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9
Q

Prime niche

A

Niche in which the organism is most successful

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10
Q

Microenvironment

A

The immediate environmental surroundings of a microbial cell or group of cells
* Physiochemical conditions are subject to rapid change
* Resources in natural environments are highly variable

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11
Q

Parasitism

A

one member in the relationship is harmed and the other benefits

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12
Q

Mutualism

A

both species benefit

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13
Q

Commensalism

A

one species benefits and the other is neither harmed nor helped

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14
Q

Biogeochemical cycle

A

Transformation of key elements by biological and chemical agents

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15
Q

Soil

A

Loose outer material of Earth’s surface

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16
Q

Types of Soil

A
  • Mineral soil
  • Organic soil
17
Q

Mineral soil

A

Derived from rock weathering and other inorganic materials

18
Q

Organic soil

A

Derived from sedimentation in bogs and marshes

19
Q

Soil composition

A
  • Inorganic material (40%)
  • Organic material (5%)
  • Air and water (50%)
  • Living organisms (5%)
20
Q

Soil structure

A
  • O Horizon:
  • A Horizon:
  • B Horizon:
  • C Horizon:
21
Q

O Horizon

A

Layer of undecomposed plant materials – top layer

22
Q

A Horizon

A

Surface soil rich in organic material, full of life

23
Q

B Horizon

A

Subsoil made of decomposed organic material and humus

24
Q

C Horizon

A

Soil base which develops directly from underlying bedrock

25
Q

Water availability of different soils

A
  • Sand: Water drains quickly
  • Silt: Retains water to the right extent
  • Clay:Water retained too well, and soil becomes anoxic
26
Q

Most important factors influencing microbial activity in soil

A
  • The availability of water in surface soils
  • Nutrient availability in subsurface soils
27
Q

Functions of bacteria/Archaea in soil

A
  • Production of the humus
  • Release of minerals from soil particles
  • Cycling of nutrients (C, N, S)
  • Nitrogen fixation
28
Q

Rhizospere

A

Soil that surrounds plant roots and receive plant secretions

29
Q

Nitrogen fixation

Start/End product? Enzyme? Conditions? Electrons required?

A
  • Conversion of atlospheric nitrogen (N2) into ammonia (NH3)
  • Reaction is catalyzed by nitrogenase complex
  • Dinitrogenase reductase is inhibited by the presence of oxygen
  • Requires 8 electrons
30
Q

Free-living nitrogen fixers

A

Clostridium, Azotobacter, Cyanobacteria

31
Q

Clostridium

A

strict anaerobe

32
Q

Azotobacter

A

Strict aerobe
* Very high rate of O2 consumption keeps the intracellular environment anaerobic

33
Q

Cyanobacteria

A

Nitrogen fixation occurs in specialized anaerobic cells (heterocysts) which lack Photosystem II

34
Q

Adaptations of heterocyts

A
  • Thick cell wall that slow down the diffusion of O2
  • The regular cells provide the heterocysts with carbohydrate
35
Q

Symbiotic nitrgen fixers

A
  • Colonization of legume roots
  • Formation of root nodules that fix nitrogen
36
Q

Nodule formation

A
  1. Recognition & attachment of bacterium to root hairs
  2. Excretion of nod factors by the bacterium
  3. Bacterial invasion of the root hair
  4. Travel to the main root via the infection thread
  5. Formation of bacteroid state within plant cell
  6. Continued plant and bacterial division, forming the mature root nodule
37
Q

O2 regulation in root nodules

A

Oxygen levels are controlled by leghemoglobin, produced by plant cells

LSCI 230: Microbiology (14 decks)

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