Week 6 Marine Symbiosis: From Deep Sea Hydrothermal Vents To Surface Ocean Phytoplankton Flashcards

1
Q

How much surface organic matter makes it to the sea floor?

A

1% so it is very barren

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2
Q

What is a source of life in the deep?

A

Hydrothermal vents

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3
Q

Where are hydrothermal vents found?

A

Typically found along mid-ocean ridges

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4
Q

What process allows so much life in the deep sea?

A

Chemolithoautotrophy

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5
Q

How does chemolithoautotrophy work at hydrothermal vents?

A

Reduced products from hydrothermal fluids after fluid-rock interactions - H2S, CH4 and H2 - may be oxidised by oxygen in normal deep-sea water for chemosynthesis

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6
Q

What are two unusual morphologies in biavalves and what are they used for?

A
  1. Extensible foot for burrowing between rocks

2. Large red gills for the symbionts

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7
Q

What is unusual about tube worms, and what question does this present?

A

They have no mouth or gut, so how do they get their energy

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8
Q

Why are tube worms trophosome tissue red?

A

Intracellular symbionts contained in bacterosytes that are required from the environment

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9
Q

How are do tube worms and other vent organisms, obtain energy?

A

Fuelled by symbiosis with chemosynthetic microorganisms

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10
Q

How do tube worms perform chemosynthesis?

A
  1. Blood circulating with haemoglobin attract H2S + O2 so they don’t react as bacteria need the energy
  2. Can do chemosynthesis and generate OM
  3. OM fed to tube worm
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11
Q

What is the relationship between CO2 fixation and H2S uptake?

A

High CO2 uptake = high H2S uptake

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12
Q

How does this image effect the primary productivity?

A

Increased CO2 uptake and H2S means higher productivity

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13
Q

What is the primary pathway for symbiont carbon fixation?

A

rTCA cycle

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14
Q

How did scientists find out that the rTCA cycle as the primary pathway for symbiont carbon fixation?

A

Stable carbon isotope data, C12 and C13 look at the ratio of the two, each reaction gives a unique signature of C fixation

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15
Q

What do the symbionts change in the rTCA cycle?

A

They modify the ATP citrate lyase

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16
Q

What did a metagenome study reveal about the symbionts in the tube worm?

A

Likely a mixotroph between the Calvin-Benson Cycle and the rTCA cycle and there is all the genes necessary for heterotrophic metabolism because they can be free living

17
Q

In the symbionts of the tube worms, which is the dominant carbon fixation pathway?

A

RTCA cycle

18
Q

In the bivalve calyptogena magnifica, how do they acquire symbionts and what extra role do their symbionts have?

A

Vertical transmission (inheritance) and S-oxidising

19
Q

In the bivalve bathymodiolus thermophilus, how do they acquire symbionts and what extra role do their symbionts have?

A
  1. Environmental acquisition

2. S and CH4 oxidant symbionts

20
Q

Where are symbionts in the mollusc and why, and what else does the mollusc still need?

A
  1. Gills, which are a gas-exchange surface

2. Still need sulfide and CH4

21
Q

There can be dual symbiosis at hydrothermal vents, what are sulphide-oxidisers called, and what are methane oxidisers called?

A
  1. Thiotrophs

2. Methanotrophs

22
Q

This image shows that hydrogenate genes overlap with thiotrophs, but not methanotrophs, what does this mean?

A

That S-oxidisers can also oxidise H2 for their chemolithoautotrophic growth

23
Q

What does this image show?

A

That those that oxidise S and H contribute to an increase in CO2 and support growth

24
Q

In mussels, when does symbiotic colonisation begin?

A

During metamorphosis

25
Q

How does symbiosis work for shrimps at vent sites?

A

They have epibionts or ecosymbionts which are not embedded in their tissues or cells

26
Q

How shrimps at vents obtain nutrition?

A
  1. Harvesting ectosymbionts

2. Ingesting their exudate after moulting

27
Q

What are the two types of bacteria at vent sites for shrimps?

A

E and y-proteobacteria, which are likely s-oxidisers

28
Q

Out of the two types of filamentous bacteria, which one is endemic?

A

E

29
Q

Why do you need N fixation in the open ocean?

A
  1. All life needs N

2. N2 is unusable to most organisms because the triple N bond is hard to break

30
Q

What are the three paradigms about N-limitation>

A
  1. N2 fixation is highest and most important to pp in open ocean regions
  2. N2 fixers aren’t competitive for other resources
  3. N2 fixation occurs where dissolved inorganic N is low
31
Q

How do we know about UCYN-A ecology?

A

Because of culture independent methods

32
Q

UCYN-A’s genome lacks photo system 2, Calvin cycle and TCA cycle, how do they survive?

A

Fish and nano sims uncovered the ectosymbiotic relationship with haptphytes

33
Q

How do UCYN-A contribute to N2 fixation?

A

High distribution and high growth rate

34
Q

Why are nutrient fixation rates higher where nutrients concentrations are the highest?

A

Shifts from trichdesmium to UCYN-A. Trichodesmiun thrives in oligotrophic waters

35
Q

What are the new paradigms regarding N2 fixation?

A
  1. N2 fixation is highest and important to pp in coastal regions
  2. N2 fixers are competitive for other resources
  3. N2 fixation occurs where dissolved inorganic nitrogen is high