Life in Extreme Environments

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Life in Extreme Environments in the Ocean
W. H. Berger Scripps Institution of Oceanography
what is extreme to some may be perfectly normal
to others and vice versa
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• Common topics re extremophiles
• Ridge Crest hot vents, giant tube worms and
  associated fauna. Sulfur-based.
• Continental margin cold vents. Bacterial mats and
  associated fauna. Carbon-based.
• Bacteria and Archea in general, in organic-rich
  environments.
• Sulfide producers and oxidizers.
• Methane producers and oxiders.

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Hot Vent Environment
Principle reaction of seawater with hot basalt
strips oxygen from sulfate dissolved in seawater
and this produces hydrogen sulfide. Bacteria gain
energy from oxidizing the hydrogen sulfide, which
leads to proliferation of these organisms in
places where these two substances meet. The
bacteria then become the base for a
chemosynthetic food chain, by being grazed and
filtered out of the water and by functioning, in
cases, as internal symbionts.
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Common misconception this food chain has no
connection to solar energy, being supported by
internal Earth heat. In fact the presence of
free oxygen in the water (for oxidizing the
hydrogen sulfide) is due to uptake of oxygen from
the air, and the presence in the air owes to the
burial of reduced carbon and therefore to
photosynthesis.
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The giant tube worms (East Pacific Rise) have no
digestive system - no mouth or gut. The worm
depends largely on symbiotic bacteria for its
nutrition.   The brown, spongy tissue filling
the inside of a tube worm is packed with bacteria
- about 285 billion bacteria per ounce of tissue.
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Cold Seep Environment
Principle reaction of interstitial water with
organic matter in sediments, and breakup of
organic matter (all mediated by bacteria)
produces alkaline solutions rich in carbon
dioxide, methane and hydrogen sulfide. Archea and
bacteria gain energy from oxidizing methane and
hydrogen sulfide, which leads to proliferation of
these organisms. The archea and bacteria then
become the base for a chemosynthetic food
chain, presumably both by being grazed and
filtered out of the water and by functioning as
symbionts.
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Common misconception this food chain has no
connection to solar energy, being supported by
internal Earth heat. In fact both methane and
hydrogen sulfide are formed as a result of
reactions involving organic carbon (buried in the
margins). Thus, they are a product of
photosynthesis, as is the presence of free oxygen
in the water.
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Arctic Ocean methane seeps with archeal mats.
Barents Sea.
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Gas hydrate carbonates
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Gas hydrate dredged from the sea floor
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Methane archea and sulfur bacteria have become a
new focus of investigation, because of their
ability to make a living in environments that are
strange to the rest of the organic
world. Especially interesting Sulfur-processing
bacteria can be extremely large. Methane-process
ing archea can mean big trouble for humankind.
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Mats of conspicuous sulfur bacteria belonging to
the genus Beggiatoa have been found in Monterey
Canyon cold seeps. Individual disk-shaped cells,
roughly 75 micrometers in diameter, form
filaments one to several centimeters long. These
bacteria have been recently described as sulfur
oxidizing, nitrate respiring autotrophs that
contain a central vacuole accounting for roughly
80 of the cellular biovolume. Nitrate is
concentrated 400fold over ambient concentration
and is presumably stored in the vacuole. In these
traits, as well as the extraordinary biomass
achieved in surficial marine sediments, these
Beggiatoa filaments show striking parallels with
those of the extensive Thioploca mats found off
the western coast of South America. Ribosomal RNA
sequence analyses of Beggiatoa spp and Thioploca
spp. support the view that the
nitrate-accumulating, vacuolate phenotype is
monophyletic.
S. C. McHattont, A. Ahmad, J. P. Barry and D. C.
Nelson University of California, Davis, and
MBARI, Moss Landing.
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Beggiatoa alba http//www-cyanosite.bio.purdue.edu
/images/images.html
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The biggest ever Thiomargarita namibiensis
One hundred times bigger than the next
largest Essentially hollow space filled with
nitrate, for storing oxygen to process hydrogen
sulfide From Namibia upwelling system extremely
high productivity
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Methane is produced in copious amounts within
organic-rich sediments in the continental
margins. At high concentrations, low
temperatures and high pressures, methane ice
can form.
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Methane ice burns if ignited, as it melts
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Ice worms, growing on methane ice in the Gulf of
Mexico Live with archeal symbionts
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Most of the hydrate is on the upper continental
slope, because that is where organic-rich
sediments are. The water has to be cold for this
ice to be stable.
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On land, methane ice is stable in permafrost
regions
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The distribution of methane ice can be traced by
the bottom simulating reflector produced at the
boundary between gas and ice. The ice forms as a
roof over the archeally generated gas-rich
interstitial fluids.
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Methane clathrates are widespread in the ocean
and also occur in some freshwater bodies.
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Take-home message
Archea have created a time-bomb deep in the
sediments of the continental slope. Their
activities can be observed from space, when gas
volcanoes emit methane and associated
hydrocarbons producing slicks on the surface of
the sea. This information is used by oil
companies to find promising places to drill for
gas and petroleum.