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Microbe from Depths Takes Life to Hottest Known Limit



 
 
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Old August 15th 03, 05:01 PM
Ron Baalke
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Default Microbe from Depths Takes Life to Hottest Known Limit

http://www.nsf.gov/od/lpa/news/03/pr0384.htm

Embargoed Until 2 p.m. Eastern Time
NSF PR 03-84 - August 14, 2003

Media contact:
Sean Kearns
(703) 292-7963

Program contact:
Matthew Kane
(703) 292-7186



Microbe from Depths Takes Life to Hottest Known Limit

Researchers find iron-reducing archaeon 'Strain 121' respires to greatness
National Science Foundation

ARLINGTON, Va.-It may be small, its habitat
harsh, but a newly discovered single-celled microbe
leads the hottest existence known to science.

Its discoverers have preliminarily named the roughly
micron-wide speck "Strain 121" for the top
temperature at which it survives: 121 degrees
Celsius, or about 250 degrees Fahrenheit.

Announcing Strain 121's record-breaking ability to
take the heat in the August 15 issue of the journal
Science, researchers Derek Lovley and Kazem
Kashefi write, "The upper temperature limit for life is
a key parameter for delimiting when and where life
might have evolved on a hot, early Earth; the depth to
which life exists in the Earth's subsurface; and the
potential for life in hot, extraterrestrial environments."

Previously, the upper known temperature limit for life
had been 113 C (235 F), a record held by another
hyperthermophilic-or extreme-heat-liking-microbe
called Pyrolobus fumarii.

The work by Lovley and Kashefi, researchers at the
University of Massachusetts, Amherst, was
supported by the National Science Foundation's Life
in Extreme Environments program. Their NSF project
may also yield clues to the formation of important ore
deposits, the remediation of toxic contaminants, and
more efficient recovery from petroleum reserves.

On a standard stovetop, water boils at 100 C, or 212
F.

Strain 121, however, comes from water at the ocean
bottom, from a surreal deep-sea realm of
hydrothermal vents. Heated to extremes by the
earth's magma, water there spouts forth through
leaks in the ocean floor. The pressure of the immense
depths prevents such hot water from turning to
steam-even as it sometimes emerges at
temperatures near 400 C (750 F).

The sample cultured by Lovley and Kashefi was
collected about 200 miles offshore from Puget Sound
and nearly a mile and a half deep in the Pacific Ocean
by a University of Washington team led by biological
oceanographer John Baross.

Baross's crew, also supported by NSF, used a
remotely operated submarine to retrieve it from the
Pacific Ocean's Juan de Fuca Ridge, a lightless
seascape where vents called "black smokers" rise up
like three- and four-story chimneys and continuously
spew a blackening brew laced with iron and sulfur
compounds. The neighborhood is called Faulty
Towers.

While suffocating, crushing, scalding, toxic and
downright abysmal by most living standards, the
arrangement is not so bad for Strain 121 and its ilk.
They are archaea, single-celled microbes similar to,
but not quite, bacteria. They often live amid extreme
heat, cold, pressure, salinity, alkalinity, and/or acidity.

Archaea literally means "ancient," and Lovley and
other biologists tend to call them "deep branchers"
because their evolutionary branch splits off trunk of
the "tree of life" close to the roots.

According to Lovley, Strain 121-it will be given a
species name after his lab finalizes the microbe's
description-uses iron the way aerobic animals use
oxygen.

"It's a novel form of respiration," Lovley says,
explaining how Strain 121 uses iron to accept
electrons. (Many archaea also use sulfur.) As oxygen
does in humans, the iron allows the microbe to burn
its food for energy. Chemically, the respiration
process reduces ferric iron to ferrous iron and forms
the mineral magnetite.

The presence of vast deposits of magnetite deep in
the ocean, its presence as a respiratory byproduct of
some archaea, and the abundance of iron on Earth
before life began all led Lovley and Kashefi to write
that "electron transport to ferrous iron may have been
the first form of microbial respiration as life evolved
on a hot, early Earth."

The researchers tested the process with Strain 121
cultures kept at 100 C in oxygen-free test tubes.

"It really isn't technically difficult. You just need
some ovens to get it hot enough-and remember not
to pick it up with your bare hands," Lovley says,
speaking from experience.

They discovered that Strain 121 grew at temperatures
from 85-121 C (185-250 F). (Meanwhile, Pyrolobus
fumarii, the former top-temperature record-holder,
wilted. After an hour at 121 C, only 1 percent of its
cells were intact and none appeared viable.)

"Growth at 121 C is remarkable," report Lovley and
Kashefi, "because sterilization at 121 C, typically in
pressurized autoclaves to maintain water in a liquid
state, is a standard procedure, shown to kill all
previously described microorganisms and
heat-resistant spores."

Not only did Strain 121 survive such autoclaving, its
population doubled in 24 hours at such heat and
pressure. While they could not detect growth at
higher temperatures, the researchers found that
cultures that spent two hours at 130 C (266 F) still
grew when transferred to a fresh medium at 103 C
(217 F), with each new single-celled member
appearing like a tiny tennis ball filled with cytoplasm
and covered with about a dozen whip-like flagella.

-NSF-

Principal Investigator: Derek Lovley, professor and
head, Department of Microbiology, University of
Massachusetts, Amherst; (415) 545-9651,
. www.geobacter.org

Additional expert: John Baross; professor,
Department of Oceanography; (206) 543-0833,



-----------------------------------------------------------------------

http://www.umass.edu/newsoffice/arch...03microbe.html


University of Massachusetts Amherst
News Release
Contact: Sarah Buchholz
August 14, 2003

Microbe Survives At Temperatures Above Sterilization Standard

Findings have implications for origins-of-life and extraterrestrial-life searches

AMHERST, Mass. - Life can survive and thrive at higher temperatures than
previously thought, remaining stable at 130°C (266°F) and reproducing at
temperatures as high as 121°C (250°F), according to research conducted by
two University of Massachusetts Amherst microbiologists. The information
gathered by Professor Derek Lovley and postdoctoral researcher Kazem Kashefi
has implications not only for understanding when and where life evolved on
Earth and how deep in the planet's subsurface life exists, but also for
determining the potential for life on other, hotter planets, particularly
Mars. Their work was funded by the National Science Foundation through a
Life in Extreme Environments grant and will appear in the Aug. 15 issue of
Science.

Prior to this research, the upper temperature known to support life had been
113°C (235°F) and the gold standard in sterilization had been 121°C, the
temperature used in autoclaves to sterilize medical equipment and in canning
to keep foods from growing toxic microorganisms. "Strain 121," as Lovley and
Kashefi have temporarily named the heat-loving organism, would thrive in an
autoclave.

"If we threw this organism in a pot of boiling water it would be happy,"
Lovley said. "Our finding changes the concept of adequate heat for
sterilization that has been in place for more than 100 years."

But don't reschedule your surgery or throw out that creamed corn yet. He
adds, "We have to actually grow it in ovens to make it grow its best.
Organisms that grow in extreme temperatures probably won't grow at body
temperature or room temperature."

Besides challenging a long-held belief about sterilization, the discovery of
Strain 121 adds to knowledge about the location of life on Earth and could
help to find it on Mars. Lovley said: "Scientifically, just knowing the
upper temperature of life is significant because it has a lot of
implications for where life will be found on Earth. In terms of biomass, the
total amount of life below the Earth's surface is greater than what we see
on the surface. If life can thrive at higher temperatures, then that's just
that much deeper in the Earth life can exist, so it's likely that the
below-surface biomass is even greater than we previously suspected."

"It's also thought that if there were life on Mars, it's almost certainly at
the subsurface," Lovley said. "This information can contribute to design
strategies for how you would look for it."

Lovley and Kashefi's work points to a form of iron, Fe(III), as a key to
discovering life at high temperatures.

Strain 121 was isolated at 100°C from a water sample from an active
hydrothermal vent in the northeast Pacific Ocean, located near the Endeavor
segment of the Juan de Fuca Ridge. Using formate as an electron donor and
Fe(III) oxide as an electron acceptor, the researchers found the strain grew
at temperatures between 85°C and 121°C.

The organism's use of iron for respiration and its tolerance of high
temperatures may provide clues to the origins of life on Earth, including
pushing back estimates of the time at which life could have evolved. Lovley
said: "Geological evidence suggests that microoganisms that use Fe(III) as
an electron acceptor are key components of the deep, hot biosphere. These
organisms use iron the way we use oxygen. The byproduct of such microbial
respiration is magnetite, and magnetite is found on very old rocks. Early
Earth was a lot hotter than now, and life probably evolved at very high
temperatures."

Strain 121 may hold industrial value, as well. "There's a lot of interest in
enzymes that can tolerate high temperatures," Lovley said. "Such enzymes may
prove useful in cleaning up `hot' contaminated waste."

-30-
 




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