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Microorganisms in natural environments Flashcards

1
Q

Growth of microbes depends on 3 factors which are:

A

resources

environmental and growth conditions

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2
Q

What defines the niche for each microbe?

A

the type and quantity of resources and physicochemical conditions of habitat

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3
Q

what is a prime niche?

A

the niche in which an organism is most successful

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4
Q

What do we call the immediate environmental surroundings of a microbial cell or group of cells?

A

the microenvironment

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5
Q

Soil particles contain many ____

A

microenvironments

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6
Q

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

A

competition and cooperation

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7
Q

What are the 3 relationships established between microbes and other organisms?

A
  • parasitism
  • mutualism
  • commensalism
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8
Q

how do we call the relationship where one member of it is harmed and the other benefits?

A

parasitism

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9
Q

how do we call the relationship where Both species benefit from it?

A

mutualism

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10
Q

how do we call the relationship where one species benefits and the other is neither harmed nor helped?

A

commensalism

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11
Q

What do we call the study of biologically mediated chemical transformations?

A

biogeochemistry

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12
Q

A typical biogeochemical cycle proceeds by _______ reactions

A

oxidation-reduction

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13
Q

What does a biogeochemical cycle define?

A

It defines the transformations of a key element by biological and chemical agents

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14
Q

_____ play critical roles in energy transformation and biogeochemical processes that result in ______ of elements to living systems. What are 3 examples of these cycles?

A

Microbes; recycling

  • carbon cycle
  • nitrogen cycle
  • sulfur cycle
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15
Q

What are the two broad groups of soil?

A
  • mineral soils

- organic soils

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16
Q

What soil is derived from sedimentation in bogs and marshes?

A

organic soils

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17
Q

What soil is derived from rock weathering (break down of rocks) and other inorganic materials?

A

mineral soils (predominate most terrestrial environments)

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18
Q

What is soil composed of?

A
  • inorganic mineral material
  • organic matter
  • air and water
  • living organisms
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19
Q

What are the different layers of soil?

A
  • O horizon
  • A horizon
  • B horizon
  • C horizon
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20
Q

What do we call the dead plant material that is resistant to decomposition and keeps water and nutrients in the soil?

A

Humus

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21
Q

Which layer of soil contains the most microorganisms?

A

the top layer (O horizon)

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22
Q

What are the 2 dominant microorganisms in soil?

A

Proteobacteria and actinobacteria

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23
Q

What is the most important factor influencing microbial activity in surface soils?

A

the availability of water

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24
Q

Which between clay, sand and silt retains water to the right extent for microbial activity and why?

A

Silt because water drains to quickly in sand and water is retained to well in clay making the soil anoxic

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25
In the top few centimetres of the soil, the soil is most rich in _____.
bacteria
26
What is the soil that surrounds plant roots and receive plant secretions making it rich in microorganisms?
Rhizosphere
27
What do we call the association of fungi with plant roots?
Mycorrhizae
28
What are prokaryotes responsible for? (4)
- the production of humus - release of minerals from soil particles (production of acids from organic compounds solubilize the minerals) - cycling of nutrients (C, N, S) - nitrogen fixation
29
CO2 is fixed by _______ land plants and marine microbes. | CO2 is returned to the atmosphere by _____ and ________ activities (use of fossil fuels)
photosynthetic; respiration; anthropogenic
30
What is the largest source of CO2 released in the atmosphere? and what is the major end product of decomposition?
microbial decomposition; CH4
31
Nitrogen fixation (N2) requires a lot of ___ because of the triple bond between N and N
ATP/energy
32
Nitrogen is a really important microbial process on earth. In the absence of _____, other organisms are dependent on nitrogen fixers.
fertilizers
33
What are the two types of nitrogen fixers?
- free-living (Cyanobacteria) | - symbiotic (Rhizobium)
34
Regarding nitrogen fixation, Which enzyme catalyzes the reaction?
nitrogenase enzyme complex
35
Who donates the electrons for nitrogen fixation and how many electrons are donated?
Pyruvate and 8 electrons are required
36
What is the final product of nitrogen fixation?
2 Ammonia (2 NH3)
37
Dinotrogenase reductase (nitrogenase enzyme complex) is inhibited by the presence of ____.
oxygen (O2)
38
What are three free-living nitrogen fixers?
- azotobacter - Beijerinckia - Clostridium (MAJOR)
39
Free-living nitrogen fixers require a soil rich in ______ to provide energy for nitrogen fixation.
organic matter
40
Clostridum is a ______
strict anaerobe
41
Azotobacter is a ________
strict aerobe
42
regarding Azotobacter, the enzyme is protected by a very high rate of ________, which keeps the intracellular environment anaerobic.
O2 consumption
43
Cyanobateria produce energy by ___________, oxygen is produced cell.
oxygenic photosynthesis
44
Nitrogen fixation occurs in specialized ________ cells (Heterocysts), which lack _______ (does not produce O2)
anaerobic; photosystem 2
45
_____ have a thick cell wall that slow down the diffusion of O2.
heterocysts
46
The regular cells (vegetative cells) provide the heterocyst with _____.
carbohydrate (pyruvate)
47
What is the most important symbioses?
the mutualistic relationship between leguminous plants (alfalfa, soybeans, peans, beans) and nitrogen-fixing bacteria
48
What is the best-known nitrogen-fixing bacteria engaging in symbiosis?
Rhizobium
49
What is formed from the colonization of legume roots and nitrogen-fixing bacteria?
root nodules that fix nitrogen
50
What are the 6 steps of nodule formation?
1: recognition and attachment of bacterium to root hairs 2: excretion of NOD FACTORS by the bacterium causing root hair to curl 3: bacterial invasion of the root hair 4: travel to the main root via the infection thread (composed of cellulose) 5: formation of BACTEROID state pithing plant cell (swollen and misshapen bacteria- fix N2). surrounded by plant cytoplasm 6: continued plant and bacterial division, forming mature root nodule
51
What are bacteroids?
- differentiated Rhyzobium cells - fix nitrogen - provide amino acids to plants
52
What to plant cells provide? (2)
- leghemoglobin | - organic acids
53
What are leghemoglobins?
O2 binding protein which controls levels of oxygen
54
What do we call the viscous sugar-rich fluid secreted by the aerial roots of some plants?
Mucilage
55
Mucilage-associated microbiota allows ________ in aerial roots.
nitrogen fixation
56
Some nitrogen is fixed by ____ in mucilage.
bacteria
57
Farmers don't have to use much fertilizers because most plants will use nitrogen compounds produced by _______ during ammonification.
free-living nitrogen fixers
58
Nitrate is ____ soluble than ammonium.
more
59
What isa source of nitrate? (NO3-)
nitrifying bacteria
60
If the soil is poorly drained and becomes waterlogged, the soil becomes _____, which promotes ______.
anaerobic; denitrification
61
Anaerobic conditions also promote ____ and _____ reduction which produce H2S which is toxic for plants.
sulfur and sulfate

Microbiology (6 decks)

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