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LEC 143 > Lecture 3b- the microbial loop > Flashcards

Lecture 3b- the microbial loop Flashcards

1
Q

Explain the feeding of guild a bacteria in the context of algae

A

-algae fix inorganic carbon from the atmosphere, and relase this from their cells as dissolved organic carbon (DOC). this is then fed on via indirect feeding by guild a bacteria

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2
Q

what is the feeding of guild a bacteria an example of? define it

A

COMMEMSALISM- the waste of one organism is used by another

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3
Q

what is bacteria (eu/prokaryote?)? size

A

single cell prokaryotes lacking a nucleus and ranging from 0.2-2 micrometers in size

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4
Q

what are the two types of bacteria in terms of carbon acquisition?

A

heterotrophic or autotrophic

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5
Q

explain the feeding of heterotrophic bacteria

A

assimilate organic carbon in the form of poc of doc

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6
Q

explain the feeding habits of autotrophic bacteria

A

assimilate inorganic carbon via photosynthesis or chemotrophy

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7
Q

Give information on guild a bacteria (eg type of carbon utilised)

A
  • the largest guild, AEROBIC bacteria
  • utilize DOC for carbon and electrons
  • are mineralisers and not decomposers, but technically break down organic carbon into co2 and water
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8
Q

what is the key genus of guild a bacteria?

A

pseudomonas

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9
Q

what is the relationship between guild a bacteria and algae?

A

mutualism

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10
Q

explain the relationship between guild a bacteria and algae

A

-algae produce DOC whih is indirectly fed on by guild a bacteria
guild a bacteria break this down and produce carbon dioxide, which is then utilized by the algae for photosynthesis

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11
Q

why is the relationship between algae and guild a bacteria not codependant?

A

carbon dioxide is not limiting within natural waters, so technically the algae don’t require guild a. Therefore its described as photocoperation

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12
Q

When is the relationship between bacterial biomass and algae biomass the strongest?

A

when there is no other source of doc within the water column. The relationship is often linear at this point.

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13
Q

what is the other source of DOC in waters? when is this most utilised?

A

humic substances that enter the water column . in locations where algae productivity is limited by light (due to a high proportion of humic substances blocking out the light) doc from humic substances become the prominent source.

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14
Q

what is humic material?

A

dead animal and plant material (POC) that is broken down into DOC by bacteria

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15
Q

finally, what are the three sources of DOC for guild a bacteria?

A
  • algae
  • decomposers
  • humic substances
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16
Q

give information on guild b bacteria

A
  • gliding/true decomposers.
  • breakdown POC into DOC
  • -found on sediment particles, rock surfaces, planktonic aggregatrs and faecla particles
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17
Q

what do guild b bacteria breakdown? (4 substances)

A

-cellulose, chitin,pectin,keratin

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18
Q

why are guild b bacteria true composers but guild a arent?

A

guild a breakdown DOC into co2 and water, but guild b breakdown POC to DOC

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19
Q

are heterotrophic protezoa predators or decomposers?

A

True predators, feed on other organisms

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20
Q

what do heterotrophic protezoa predate?

A

-Algae and guild a bacteria

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21
Q

describe heterotrphic protezoa (eg. eukaryotes, aerobic/anaerobic etc)

A
  • eukaryotic

- anaerobic

22
Q

what are the three types of heterotrophic protezoa?

A
  • flagellates
  • amoebae
  • cilliates
23
Q

what are the only two anaerobic protezoa?

A

-sulphur cilliates and one flagellate

24
Q

describe naked ameoba (motion, attachment, feeding habit)

A
  • latin name ameoba proteus
  • move via cytoplasm streaming. this is done via pseodopodia
  • can only move on the surface of substrates, and use pseudopods to catch non-motile prey
  • known as feeding by rapotoral feeding
25
Q

How do naked aemeboe feed?

A

Raptoral feeding

26
Q

describe briefly what Pseudopodia is

A

where cytoplasm-filled parts of the cell membrane are able to temporarily change their form to move

27
Q

where do testae amoebae live?

A

in the water column (pelagic)

28
Q

what are testae amoebae enclosed in? give information on the two types

A
  • they are enclosed in a shell of calcareous or siliceous material
  • two groups: radalorians and foraminifera
29
Q

how do testae amoebae catch food?

A
  • they project heir intrashellular cytoplasm that catches prey that swims by
  • once prey is caught, the cytoplasm is retracted back into the shell
30
Q

what are the two types of feeding utilised by testae and naked amoebae?

A
  • naked utilised raptoral feeding

- testae utilise diffusion feeding

31
Q

describe the feeding patterns and movement etc of zooflagellates (heterotrophic flagellates)

A
  • use “hairy” flagellums for feeding and swimming
  • most efficent when attatched to a surface
  • prey injested via pseudopods within the flagellum
32
Q

explain loricas and zooflagellates

A

-zooflagellates produce loricas out of sillica strips and uses this to float in a basket (only in marine systems)

33
Q

why are zooflagellates most effective when attatching to a surface/inside a lorica?

A

-they need to make currents for swimming and feeding. they can therefore focus on making the most effective currents for food acquisition

34
Q

Describe cilliates

  • how they swim
  • prehistoric features
  • nucleus
A
  • the most diverse group of protezoa
  • covered in cillia (hairs) used for swimming
  • prehistoric mouths called CYTOSTOME and anus CYTOPROCT
  • two types of nucleus: macronucleus and micronucleus
35
Q

What happens to cilliate micronuclei in mating?

A

-micronuclei are transferred between cells in sex, leading to high diversity

36
Q

explain the functional role of protezoa in marine environments (C:N:P ratio)

A
  • they keep the C:N:P ratio strictly at 50:10:1
  • this is done by pumping out inorganic N and P when carbon is lost in respiration (as this changes the ratio)
  • their functional role is also to eat algae+ bacteria and provide food for invertebrates
37
Q

how does the microbial loop appear in anaerobic environments?

A
  • anaerobic bacteria serve as primary producers, and sulphur cilliates are the ONLY protezoa
38
Q

describe guild F bacteria

A
  • green and purple sulfur bacteria
  • only exist in anaerobic environments, and carry ANAEROBIC PHOTOSYNTHESIS
  • core genus: Chromatium
39
Q

what type of light do guild F bacteria utilise? why?

A

-utilise far-red light, as “normal ligh” is often limiting at the bottom of lake environments (where anaerobic conditions are most commonly found)

40
Q

what do guild f bacteria produce from photosynthesis?

A

-doc

41
Q

what do guild f bacteria use in place of oxygen as their electron fixer?

A

-hydrogen sulfide

42
Q

Describe guild E bacteria

A
  • anaerobic
  • use sulphate to fix electrons in respiration processes
  • produce DOC
  • also carry out anerobic respiration
43
Q

Explain the relationship between guild E and guild F bacteria in the anaerobic environment

A

-guild F bacteria produce SO4, and guild E bacteria produce HS2. these are the substances that the other requires as their electron fixer, so subsequently they have a COMMENSALISM relationship.

44
Q

why are guild E bacteria not limited by carbon

A

-DOC is produced in house by guild F, and it diffuses down by the aerobic layer

45
Q

What type of bacteria carry out methanogenesis?

A

-Guild G bacteria

46
Q

What is methanogenesis, where does it occur, and what bacteria do it?

A
  • methanogenesis is the formation of methane, and can only be carried out in anaerobic environments
  • formed directly from carbon dioxide and hydrogen
47
Q

why is there limited out of water methane diffusion?

A

-bacteria in the aerobic zone will utilise it as it diffuses out (for carbon) so limited amounts are released from the water body

48
Q

how to protezoa operate as predators in the anaerobic zone? (eg. hydrogenosomes)

A

-sulphur cilliates are the only predators
-adapted their mitochondria to form HYDROGENOSOMES which carry out anaerobic respiration
-contain symbiotic methanogenic bacteria (guild b)
-

49
Q

how did hydrogenosomes form?

A

-from a past symbiotic relationship between cilliates and anaerobic bacteria

50
Q

how do hydrogenosomes respire(reactants and products)?

A

-take pyruvate and convert it into acetate. this produces hydrogen and carbon dioxde in the process

51
Q

how is methane produced from sulphur cilliates?

A
  • methane producing bacteria that live on them utilised the produced hydrogen and carbon dioxide from the hydrogenosomes, converting it into methane
  • alternatively, they break down the acetate into hydrogen and carbon dioxide, which are then used to produce methane
52
Q

what are the primary producers in aerobic and anaerobic environments?

A

-aerobic: algae

Anaerobic: guild F

LEC 143 (14 decks)

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