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Microbiology > Microorganisms in natural environments > Flashcards

Microorganisms in natural environments Flashcards

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Biology 101 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
Q

In the top few centimetres of the soil, the soil is most rich in _____.

A

bacteria

26
Q

What is the soil that surrounds plant roots and receive plant secretions making it rich in microorganisms?

A

Rhizosphere

27
Q

What do we call the association of fungi with plant roots?

A

Mycorrhizae

28
Q

What are prokaryotes responsible for? (4)

A
  • 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
Q

CO2 is fixed by _______ land plants and marine microbes.

CO2 is returned to the atmosphere by _____ and ________ activities (use of fossil fuels)

A

photosynthetic; respiration; anthropogenic

30
Q

What is the largest source of CO2 released in the atmosphere? and what is the major end product of decomposition?

A

microbial decomposition; CH4

31
Q

Nitrogen fixation (N2) requires a lot of ___ because of the triple bond between N and N

A

ATP/energy

32
Q

Nitrogen is a really important microbial process on earth. In the absence of _____, other organisms are dependent on nitrogen fixers.

A

fertilizers

33
Q

What are the two types of nitrogen fixers?

A
  • free-living (Cyanobacteria)

- symbiotic (Rhizobium)

34
Q

Regarding nitrogen fixation, Which enzyme catalyzes the reaction?

A

nitrogenase enzyme complex

35
Q

Who donates the electrons for nitrogen fixation and how many electrons are donated?

A

Pyruvate and 8 electrons are required

36
Q

What is the final product of nitrogen fixation?

A

2 Ammonia (2 NH3)

37
Q

Dinotrogenase reductase (nitrogenase enzyme complex) is inhibited by the presence of ____.

A

oxygen (O2)

38
Q

What are three free-living nitrogen fixers?

A
  • azotobacter
  • Beijerinckia
  • Clostridium (MAJOR)
39
Q

Free-living nitrogen fixers require a soil rich in ______ to provide energy for nitrogen fixation.

A

organic matter

40
Q

Clostridum is a ______

A

strict anaerobe

41
Q

Azotobacter is a ________

A

strict aerobe

42
Q

regarding Azotobacter, the enzyme is protected by a very high rate of ________, which keeps the intracellular environment anaerobic.

A

O2 consumption

43
Q

Cyanobateria produce energy by ___________, oxygen is produced cell.

A

oxygenic photosynthesis

44
Q

Nitrogen fixation occurs in specialized ________ cells (Heterocysts), which lack _______ (does not produce O2)

A

anaerobic; photosystem 2

45
Q

_____ have a thick cell wall that slow down the diffusion of O2.

A

heterocysts

46
Q

The regular cells (vegetative cells) provide the heterocyst with _____.

A

carbohydrate (pyruvate)

47
Q

What is the most important symbioses?

A

the mutualistic relationship between leguminous plants (alfalfa, soybeans, peans, beans) and nitrogen-fixing bacteria

48
Q

What is the best-known nitrogen-fixing bacteria engaging in symbiosis?

A

Rhizobium

49
Q

What is formed from the colonization of legume roots and nitrogen-fixing bacteria?

A

root nodules that fix nitrogen

50
Q

What are the 6 steps of nodule formation?

A

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
Q

What are bacteroids?

A
  • differentiated Rhyzobium cells
  • fix nitrogen
  • provide amino acids to plants
52
Q

What to plant cells provide? (2)

A
  • leghemoglobin

- organic acids

53
Q

What are leghemoglobins?

A

O2 binding protein which controls levels of oxygen

54
Q

What do we call the viscous sugar-rich fluid secreted by the aerial roots of some plants?

A

Mucilage

55
Q

Mucilage-associated microbiota allows ________ in aerial roots.

A

nitrogen fixation

56
Q

Some nitrogen is fixed by ____ in mucilage.

A

bacteria

57
Q

Farmers don’t have to use much fertilizers because most plants will use nitrogen compounds produced by _______ during ammonification.

A

free-living nitrogen fixers

58
Q

Nitrate is ____ soluble than ammonium.

A

more

59
Q

What isa source of nitrate? (NO3-)

A

nitrifying bacteria

60
Q

If the soil is poorly drained and becomes waterlogged, the soil becomes _____, which promotes ______.

A

anaerobic; denitrification

61
Q

Anaerobic conditions also promote ____ and _____ reduction which produce H2S which is toxic for plants.

A

sulfur and sulfate

Microbiology (6 decks)

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