[meteorite-list] Mars May Be Cozy Place for Hardy Microbes

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Oct 19 15:46:18 2006
Message-ID: <200610191946.MAA07033_at_zagami.jpl.nasa.gov>

http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/48/full/

Release Date: 1:00PM (EDT) October 19, 2006
Release Number: STScI-2006-48

Contact:

Neill Reid
Space Telescope Science Institute, Baltimore, Md.
(Phone: 410-338-4971, E-mail: inr_at_stsci.edu

Shiladitya DasSarma
University of Maryland Biotechnology Institute, Baltimore, Md.
(Phone: 410-234-8847; E-mail: dassarma_at_umbi.umd.edu)

Mars May Be Cozy Place for Hardy Microbes

A class of especially hardy microbes that live in some of the harshest
Earthly environments could flourish on cold Mars and other chilly
planets, according to a research team of astronomers and microbiologists.

In a two-year laboratory study, the researchers discovered that some
cold-adapted microorganisms not only survived but reproduced at 30
degrees Fahrenheit, just below the freezing point of water. The microbes
also developed a defense mechanism that protected them from cold
temperatures. The researchers are members of a unique collaboration of
astronomers from the Space Telescope Science Institute and
microbiologists from the University of Maryland Biotechnology
Institute's Center of Marine Biotechnology in Baltimore, Md. Their
results appear on the International Journal of Astrobiology website.

"The low temperature limit for life is particularly important since, in
both the solar system and the Milky Way Galaxy, cold environments are
much more common than hot environments," said Neill Reid, an astronomer
at the Space Telescope Science Institute and leader of the research
team. "Our results show that the lowest temperatures at which these
organisms can thrive fall within the temperature range experienced on
present-day Mars, and could permit survival and growth, particularly
beneath Mars's surface. This could expand the realm of the habitable
zone, the area in which life could exist, to colder Mars-like planets."

Most stars in our galaxy are cooler than our Sun. The zone around these
stars that is suitable for Earth-like temperatures would be smaller and
narrower than the so-called habitable zone around our Sun. Therefore,
the majority of planets would likely be colder than Earth.

In their two-year study, the scientists tested the coldest temperature
limits for two types of one-cell organisms: halophiles and methanogens.
They are among a group of microbes collectively called extremophiles,
so-named because they live in hot springs, acidic fields, salty lakes,
and polar ice caps under conditions that would kill humans, animals, and
plants. Halophiles flourish in salty water, such as the Great Salt Lake,
and have DNA repair systems to protect them from extremely high
radiation doses. Methanogens are capable of growth on simple compounds
like hydrogen and carbon dioxide for energy and can turn their waste
into methane.

The halophiles and methanogens used in the experiments are from
Antarctic lakes. In the laboratory, the halophiles displayed significant
growth to 30 degrees Fahrenheit (minus 1 degree Celsius). The
methanogens were active to 28 degrees Fahrenheit (minus 2 degrees Celsius).

"We have extended the lower temperature limits for these species by
several degrees," said Shiladitya DasSarma, a professor and a leader of
the team at the Center of Marine Biotechnology, University of Maryland
Biotechnology Institute. "We had a limited amount of time to grow the
organisms in culture, on the order of months. If we could extend the
growth time, I think we could lower the temperatures at which they can
survive even more. The brine culture in which they grow in the
laboratory can remain in liquid form to minus 18 degrees Fahrenheit
(minus 28 degrees Celsius), so the potential is there for significantly
lower growth temperatures."

The scientists also were surprised to find that the halophiles and
methanogens protected themselves from frigid temperatures. Some arctic
bacteria show similar behavior.

"These organisms are highly adaptable, and at low temperatures they
formed cellular aggregates," DasSarma explained. "This was a striking
result, which suggests that cells may 'stick together' when temperatures
become too cold for growth, providing ways of survival as a population.
This is the first detection of this phenomenon in Antarctic species of
extremophiles at cold temperatures."

The scientists selected these extremophiles for the laboratory study
because they are potentially relevant to life on cold, dry Mars.
Halophiles could thrive in salty water underneath Mars's surface, which
can remain liquid at temperatures well below 32 degrees Fahrenheit (0
degrees Celsius). Methanogens could survive on a planet without oxygen,
such as Mars. In fact, some scientists have proposed that methanogens
produced the methane detected in Mars's atmosphere.

"This finding demonstrates that rigorous scientific studies on known
extremophiles on Earth can provide clues to how life may survive
elsewhere in the universe," DasSarma said.

The researchers next plan to map the complete genetic blueprint for each
extremophile. By inventorying all of the genes, scientists will be able
to determine the functions of each gene, such as pinpointing the genes
that protect an organism from the cold.

Many extremophiles are evolutionary relics called Archaea, which may
have been among the first homesteaders on Earth 3.5 billion years ago.
These robust extremophiles may be able to survive in many places in the
universe, including some of the roughly 200 worlds around stars outside
our solar system that astronomers have found over the past decade. These
planets are in a wide range of environments, from so-called "hot
Jupiters," which orbit close to their stars and where temperatures
exceed 1,800 degrees Fahrenheit (1,000 degrees Celsius), to gas giants
in Jupiter-like orbits, where temperatures are around minus 238 degrees
Fahrenheit (minus 150 degrees Celsius).

The discovery of planets with huge temperature disparities has
scientists wondering what environments could be hospitable to life. A
key factor in an organism's survival is determining the upper and lower
temperature limits at which it can live.

Although Martian weather conditions are extreme, the planet does share
some similarities with the most extreme cold regions of Earth, such as
Antarctica. Long regarded as essentially barren of life, recent
investigations of Antarctic environments have revealed considerable
microbial activity. "The Archaea and bacteria that have adapted to these
extreme conditions are some of the best candidates for terrestrial
analogues of potential extraterrestrial life; understanding their
adaptive strategy, and its limitations, will provide deeper insight into
fundamental constraints on the range of hospitable environments,"
DasSarma said.

The team's research was supported through grants from the Space
Telescope Science Institute's Director's Discretionary Research Fund, a
National Science Foundation, and the Australian Research Council.

The Space Telescope Science Institute is operated for NASA by the
Association of Universities for Research in Astronomy, Inc., Washington.

One of five centers forming the University of Maryland Biotechnology
Institute (UMBI) the Center of Marine Biotechnology, located in
Baltimore's Inner Harbor, employs researchers who apply the tools of
modern biology and biotechnology to study, protect, and enhance marine
and estuarine resources.

With research centers in Baltimore, Rockville, and College Park, the
University of Maryland Biotechnology Institute is the newest of 13
institutions forming the University System of Maryland. UMBI has 85
ladder-ranked faculty and a 2006 budget of $60 million. Celebrating the
institution's 20th year of service to Maryland and the world, UMBI is
led by microbiologist and former biotechnology executive Dr. Jennie C.
Hunter-Cevera. For more information visit http://www.umbi.umd.edu.
Received on Thu 19 Oct 2006 03:46:15 PM PDT