Soil Microbiology Flashcards

1
Q

ecosystem

A

the sum of all organisms and abiotic factors in a particular environment. Complex of plants, animals, abiotic, and microbial communities which interact as a *functional unit

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2
Q

habitat

A

portion of an ecosystem where a community could reside. An ecosystem contains many different habitats.

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3
Q

population

A

group of microorganisms of the same species residing in the same space

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4
Q

community

A

group of populations

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5
Q

species richness

A

total number of different species present

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6
Q

species abundance

A

the proportion of each species in an ecosystem (amount of individuals in each species)

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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. It supplies nutrients and conditions for growth

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9
Q

microenvironment

A
  • the immediate environmental surroundings of a microbial cell or group of cells.
  • soil particles contain many microenvironments
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10
Q

competition and cooperation

A

occur between microbes in natural systems and between microbes and higher organisms.

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11
Q

parasitism, mutualism, commensalism

A

many microbes establish relationships with other organisms

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12
Q

biogeochemistry

A

the study of biologically mediated chemical transformations

-biogeochemical cycles

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13
Q

mineral soils

A

derived from rock weathering and other inorganic materials.

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14
Q

organic soils

A

derived from sedimentation in bogs and marshes

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15
Q

composition of soil

A
  • air and water
  • inorganic mineral matter
  • organic matter
  • living organsims
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16
Q

humus

A

dead plant material that is resistant to decomposition

  • keeps water and nutrients in the soil
  • good for soil fertility
17
Q

top few centimeters of soil contain..

A

**bacteria: up to 2.5x10^9 (*per g of soil)

18
Q

rhizosphere

A

soil that surrounds plant roots and receive plant secretions

19
Q

mycorrhizae

A

association of fungi with plant roots

20
Q

**Azotobacter

A
  • widespread in soil, require a soil rich in organic matter to provide energy for nitrogen fixation
  • produce ammonia that can be used in plants (NH3 dissolves in water to produce NH4)
21
Q

Nitrogen fixation

A
  • only certain prokaryotes can fix N2 because a lot of energy is required to break the triple bond
  • ammonia is the final product and used to produce amino acids
  • **Dinitrogenase reductase is inhibited by the presence of oxygen
22
Q

Nodule formation

A
  1. recognition and attachment of bacterium to root hairs
  2. excretion of *node factors by the bacterium
  3. bacterial invasion of the root hair
  4. travel to the main root via the infection thread (tube composed of cellulose)
  5. formation of *bacteroid state *within plant cell (swollen and misshapen bacteria fix N2). Surrounded by plant cytoplasm
  6. continued plant and bacterial division, forming the mature root nodule
23
Q

Cyanobacteria

A
  • nitrogen fixation in heterocysts (anaerobic) that do not have photosystem II.
  • heterocysts have a thick cell wall and slow diffusion of O2
24
Q

symbiosis and nitrogen fixers

A

-leguminous plants and bacteria