at Hydrothermal Vents
Tiny, single-celled bacteria comprise most life on
this planet, yet we have discovered only about five percent of its
diversity. We know even less about bacteria thriving at deep-sea
Anna-Louise Reysenbach takes a bacterial sample from a hot spring
in Yellowstone National Park. She researches thermophiles in Yellowstones hot springs as well as at hydrothermal vent sites found in the Pacific,
Atlantic and Indian Oceans. Photograph: O. Louis Mazzatenta.
at hydrothermal vents inhabit almost everything: rocks, the seafloor,
even the inside of animals like mussels. All are living under
extreme pressure and temperature changes. Perhaps the oddest
and toughest bacteria at vents are the heat-loving thermophiles. Temperatures
well above 662°F (350°C) are not uncommon at vents. The world
record; for life growing at high temperatures is 235°F
(113¼C), a record held by a type of thermophile known
as a hyperthermophile. These themophiles grow best above 176°F
Many thermophiles have a simple diet, based solely on the metals,
gases and minerals that comprise the hydrothermal vent fluid.
For example, on Knorr we are
growing thermophiles collected from vent sites in the Indian Ocean that require
only sulfur, hydrogen and carbon dioxide.
is a microscopic view of a bacterial community from a hot spring
in the Azores, an island in the Atlantic Ocean. Notice all the
sizes and shapes of the bacteria, yet none of them have names
because none of them have been identified. Scale bar is 1 µm
(1/1000 of a mm). Photograph: Paula Aguilar.
shows a cross-section view of a thermophile. Notice all the
viruses in the cell. Viruses are much smaller than bacteria
and are abundant at deep-sea vents. Photograph: Terry Beveridge.
may assist in creating terraced rock structures like these,
located at Mammoth Hot Springs, Yellowstone National Park, USA.
Astrobiologists are interested in how these rocks because it
gives them insights into how rocks may form on other planets.
stringy thermophiles make sulfur and with time they harden and
fossilize into rock.
of thermophiles clump together and create this yellow-mustard
color at Mushroom Hot Spring in Yellowstone National Park.
The thermophiles we study today are modern relatives
of ancient thermophiles. Think about what types of organisms might
have lived more than 3.5 billion years ago. At first, Earth was a
hot, volcanically-active planet. Slowly, over the years, it cooled
and formed the lands and seas we know today. There are numerous theories
that suggest thermophiles -- and life -- may have originated at deep-sea
vents early in Earths history.
But Earth is not the only place in our solar system where life
could evolve and exist. All life as we know it requires water,
an energy source and a carbon source. Both Mars and one of Jupiters
moons, Europa, may have these conditions, and thus make good targets
to look for past and present life.
Can studying thermophiles at deep-sea vents help us in our search
for evidence of past and present life on other planets? Scientists
think the answer is yes. Clues on Mars landscape suggest that water once flowed there. Also, Mars
still has an ice cap and there may be liquid water deep in the planets
interior. There is also geologic evidence that Mars once had volcanoes, much
larger and more powerful than the volcanoes we know today on Earth. Astrobiologists
think that any evidence of life found on other planets will be bacteria-like,
living beneath the planet or moon surface and using chemical energy for their
Thermophiles are also useful to us on a daily basis. Thermophiles make protein
molecules called enzymes that speed up chemical reactions. Enzymes from thermophiles
are useful in high temperature situations. Enzymes are added to many washing
detergents because they can eat away the oily stains on clothing
in hot water.
research is another area where thermophiles are used. The thermophilic
DNA enzyme Taq polymerase, an enzyme that makes many copies
of DNA pieces, was first obtained from the thermophile Thermus aquaticus from
Yellowstone National Park. This thermophile creates the yellow-mustard
color found in many hot springs around Yellowstones Lower Geyser
Biotechnology companies have also been selling similar enzymes from deep-sea
hydrothermal vent thermophiles. These enzymes are called Pfu polymerase
and have helped us to discover genetic diseases, find criminals who may have
left hair or blood at the crime scene and sequence the entire human genome.
On this expedition, we use enzymes to try and identify the bacteria
we collect from hydrothermal vents. Like detectives using genetic
methods to find criminals, we look for a specific piece of genetic
DNA that identifies our organisms, and then we make many copies
of the gene. Using this process, we are finding many new types
of bacteria at deep-sea vents that we have never seen before. Its
amazing to think what we might learn from them.
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