Extreme Microbes Found in Crystals Buried 200 Feet Beneath the Sea of Japan
Scanning electron microscopy
(SEM) of microdolomite grains (490 times magnification) recovered from
inside a gas hydrate beneath nearly 200 feet of seafloor sediment.
Credit: Glen Snyder, Meiji University Gas Hydrate Research Laboratory
Buried hundreds of feet under the ocean bottom in the Sea of Japan,
where bone-chilling temperatures and intense pressure discourage most
forms of life, there live some very hardy microbes. Their deep-sea
secret? They hunker down in pockets inside tiny mineral grains, which
are then sealed into deep-sea crystals.
Scientists discovered the crystal-encased microbes during an expedition
to Joetsu Basin to sample gas hydrates — crystalline solids of gas and
water that form in the ocean under high pressure and intense cold. They
presented their findings in December at the annual conference of the
American Geophysical Union (AGU).
After the researchers examined massive hydrates collected at the sea
bottom off Japan's western coast, they found that some of the hydrates
contained tiny grains of a mineral called dolomite. And dark spots in
the dolomite hinted that there was yet another surprise to come,
researcher Glen Snyder, a professor at Meiji University in Japan, told
Live Science at the conference. [Extreme Life on Earth: 8 Bizarre Creatures]
While the hydrates were quite large, measuring up to 16 feet (5 meters)
long, the dolomite grains were tiny — about 30 microns, or 0.001
inches, in diameter, Snyder said. The researchers discovered the
dolomite in residue left behind after they chemically separated the
hydrates into gas and water.
Fluorescent staining of dark cores in the grains revealed that they
contained genetic material, which glowed under UV light. It represented
"high concentrations" of microbial matter, the scientists reported at
the AGU meeting.
Microbes are known to live around gas hydrates;
nevertheless, it was entirely unexpected to find these nested microbial
tenants inside mineral grains that were inside the hydrates, Snyder
said. The staining couldn't show whether the microbes were alive or not,
and microbiologists are currently working to interpret the microbial
DNA and identify the microbes, according to the presentation.
Because the microbes are effectively sealed inside a "pristine
environment," scientists can be fairly certain that the organisms were
naturally present in that area, and were not accidentally introduced by scientific equipment or human intervention, according to Snyder.
Digital light microscopy of dolomite grains reveals organic matter trapped inside the cores.
Credit: G. Snyder, Meiji
University Gas Hydrate Research Laboratory/Kentaro Tanaka, University of
Tokyo Atmosphere and Ocean Research Institute
Though this is the only known evidence of microorganisms encased in
dolomite crystals, there may be other microbial opportunists elsewhere
in the oceans, growing in saline chambers in gas hydrates, the
scientists reported.
In fact, temperature and pressure conditions on other planets such as
Mars could also be just right for shaping gas hydrates, which could
potentially serve as homes for Martian microbes, the researchers wrote.
Microbe-housing dolomites discovered in the sea of Japan aren't very
different from minerals found in Martian meteorites; this suggests that
the Red Planet might present opportunities for microbial life to survive
as it does inside dolomites on Earth, Snyder said.
