The surprise here is that the biome
of the deep sea smokers is also able to use hydrogen which is commonly produced
by the smokers. I do not know if any of
this will translate into improved hydrogen systems on land, but we now see
nature doing it rather well.
Instead of oxygen, we have a
chemistry based on hydrogen, methane and hydrogen sulphide. It certainly makes the production of life on
an oxygen free world rather plausible.
Take a hot rock like Venus and just add water.
The real point is that we now
have the unimaginable in a life form that is fueled by hydrogen. I wonder if it exists on Jupiter?
Hydrogen highway in the deep sea
by Staff Writers
When hydrothermal vents were
first discovered more than 30 years ago, researchers were astounded to find
that they were inhabited by lush communities of animals such as worms, mollusks
and crustaceans, most of which were completely unknown to science.
The search for new energy sources to power mankind's increasing needs
is currently a topic of immense interest. Hydrogen-powered
fuel cells are considered one of the most promising clean energy alternatives.
While intensive research efforts have gone into developing ways to harness
hydrogen energy to fuel our everyday lives, a natural example of a living
hydrogen-powered 'fuel cell' has gone unnoticed.
During a recent expedition to hydrothermal vents in the deep sea,
researchers from the MaxPlanck Institute of
Marine Microbiology and the Cluster of Excellence MARUM discovered mussels that
have their own on-board 'fuel cells', in the form of symbiotic bacteria that
use hydrogen as an energy source.
Their results, which appear in the current issue of Nature, suggest
that the ability to use hydrogen as a source of energy is widespread in
hydrothermal vent symbioses.
Deep-sea hydrothermal vents are formed at mid-ocean spreading centers
where tectonic plates drift apart and new oceanic crust is created by magma
rising from deep within the Earth.
When seawater interacts with hot rock and rising magma, it becomes
superheated, dissolving minerals out of the Earth's crust. At hydrothermal
vents, this superheated energy-laden seawater gushes back out into the ocean at
temperatures of up to 400 degrees Celsius, forming black smoker chimneys where
it comes into contact with cold deep-sea water.
These hot fluids deliver inorganic compounds such as hydrogen sulfide,
ammonium, methane,
iron and hydrogen to the oceans. The organisms living at hydrothermal vents
oxidize these inorganic compounds to gain the energy needed to create organic
matter from carbon dioxide.
Unlike on land, where sunlight provides the energy for photosynthesis,
in the dark depths of the sea, inorganic chemicals provide energy for life in a
process called chemosynthesis.
When hydrothermal vents were first discovered more than 30 years ago,
researchers were astounded to find that they were inhabited by lush communities
of animals such as worms, mollusks and crustaceans, most of which were
completely unknown to science.
The first to investigate these animals quickly realized that the key to
their survival was their symbiotic association with chemosynthetic microbes,
which are the on-board power plants for hydrothermal vent animals.
Until now, only two sources of energy were known to power
chemosynthesis by symbiotic bacteria at hydrothermal vents: Hydrogen sulfide,
used by sulfur-oxidizing symbionts, and methane, used by methane-oxidizing
symbionts.
"We have now discovered a third energy source" says Nicole
Dubilier from the Max Planck Institute of
Marine Microbiology in Bremen
The discovery began at the Logatchev hydrothermal vent field, at 3000 m
depth on the Mid-Atlantic Ridge, an undersea mountain range halfway between the
Caribbean and the Cape Verde
Islands
According to Jillian Petersen, a researcher with Nicole Dubilier,
"our calculations show that at this hydrothermal vent, hydrogen oxidation
could deliver seven times more energy than methane oxidation, and up to 18
times more energy than sulfide oxidation".
In the gills of the deep-sea mussel Bathymodiolus puteoserpentis, one
of the most abundant animals at Logatchev, the researchers discovered a
sulfur-oxidizing symbiont that can also use hydrogen as an energy source.
To track down these hydrogen-powered on-board 'fuel cells' in the
deep-sea mussels, the researchers deployed two deep-sea submersibles,
MARUM-QUEST from MARUM at the University of Bremen, and KIEL 6000 from
IFM-GEOMAR in Kiel. With the help of these remotely-driven submersibles, they
sampled mussels from sites kilometers below the sea surface.
Their ship-board experiments with live samples showed that the mussels
consumed hydrogen. Once the samples were back in the laboratory on land, they
were able to identify the mussel symbiont hydrogenase, the key enzyme for
hydrogen oxidation, using molecular techniques.
The mussel beds at Logatchev form a teeming expanse that covers
hundreds of square meteres and contains an estimated half a million mussels.
"Our experiments show that this mussel population could consume up to 5000
liters of hydrogen per hour" according to Frank Zielinski, a former
doctoral student in Nicole Dubilier's Group in Bremen, who now works as a
post-doctoral researcher at the Helmholtz Centre for Environmental Research in
Leipzig.
The deep-sea mussel symbionts therefore play a substantial role as the
primary producers responsible for transforming geofuels to biomass in these
habitats.
"The hydrothermal vents along the mid-ocean ridges that emit large
amounts of hydrogen can therefore be likened to a hydrogen highway with
fuelling stations for symbiotic primary production" says Jillian Petersen.
Even the symbionts of other hydrothermal vent animals such as the
giant tubeworm Riftia pachyptila and the shrimp Rimicaris exoculata have the
key gene for hydrogen oxidation, but remarkably, this had not been previously
recognized.
"The ability to use hydrogen as an energy source seems to be
widespread in these symbioses, even at hydrothermal vent sites with low amounts
of hydrogen" says Nicole Dubilier.
Jillian M. Petersen, Frank U. Zielinski, Thomas Pape, Richard Seifert,
Cristina Moraru, Rudolf Amann, Stephane Hourdez, Peter R. Girguis, Scott D.
Wankel, Valerie Barbe, Eric Pelletier, Dennis Fink, Christian Borowski,
Wolfgang Bach, Nicole Dubilier (2011): Hydrogen is an energy source for
hydrothermal vent symbioses. Nature 474, 11 August 2011. doi:
10.1038/nature10325. This study was supported by the Max Planck Society, the
German Research Foundation (Priority program 1144: "From Mantle to Ocean:
Energy-, Material- and Life Cycles at Spreading Axes''), and the Cluster of Excellence
"The Ocean in the Earth System" at MARUM, Bremen
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