Week 6 Marine Symbiosis: From Deep Sea Hydrothermal Vents To Surface Ocean Phytoplankton Flashcards
(35 cards)
How much surface organic matter makes it to the sea floor?
1% so it is very barren
What is a source of life in the deep?
Hydrothermal vents
Where are hydrothermal vents found?
Typically found along mid-ocean ridges
What process allows so much life in the deep sea?
Chemolithoautotrophy
How does chemolithoautotrophy work at hydrothermal vents?
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
What are two unusual morphologies in biavalves and what are they used for?
- Extensible foot for burrowing between rocks
2. Large red gills for the symbionts
What is unusual about tube worms, and what question does this present?
They have no mouth or gut, so how do they get their energy
Why are tube worms trophosome tissue red?
Intracellular symbionts contained in bacterosytes that are required from the environment
How are do tube worms and other vent organisms, obtain energy?
Fuelled by symbiosis with chemosynthetic microorganisms
How do tube worms perform chemosynthesis?
- Blood circulating with haemoglobin attract H2S + O2 so they don’t react as bacteria need the energy
- Can do chemosynthesis and generate OM
- OM fed to tube worm
What is the relationship between CO2 fixation and H2S uptake?
High CO2 uptake = high H2S uptake
How does this image effect the primary productivity?
Increased CO2 uptake and H2S means higher productivity
What is the primary pathway for symbiont carbon fixation?
rTCA cycle
How did scientists find out that the rTCA cycle as the primary pathway for symbiont carbon fixation?
Stable carbon isotope data, C12 and C13 look at the ratio of the two, each reaction gives a unique signature of C fixation
What do the symbionts change in the rTCA cycle?
They modify the ATP citrate lyase
What did a metagenome study reveal about the symbionts in the tube worm?
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
In the symbionts of the tube worms, which is the dominant carbon fixation pathway?
RTCA cycle
In the bivalve calyptogena magnifica, how do they acquire symbionts and what extra role do their symbionts have?
Vertical transmission (inheritance) and S-oxidising
In the bivalve bathymodiolus thermophilus, how do they acquire symbionts and what extra role do their symbionts have?
- Environmental acquisition
2. S and CH4 oxidant symbionts
Where are symbionts in the mollusc and why, and what else does the mollusc still need?
- Gills, which are a gas-exchange surface
2. Still need sulfide and CH4
There can be dual symbiosis at hydrothermal vents, what are sulphide-oxidisers called, and what are methane oxidisers called?
- Thiotrophs
2. Methanotrophs
This image shows that hydrogenate genes overlap with thiotrophs, but not methanotrophs, what does this mean?
That S-oxidisers can also oxidise H2 for their chemolithoautotrophic growth
What does this image show?
That those that oxidise S and H contribute to an increase in CO2 and support growth
In mussels, when does symbiotic colonisation begin?
During metamorphosis
