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2010-12-03 05:51:41
By Maggie Fox, Health and Science Editor Maggie Fox, Health And Science Editor
Thu Dec 2, 3:09 pm ET
WASHINGTON (Reuters) A strange, salty lake in California has yielded an
equally strange bacterium that thrives on arsenic and redefines life as we know
it, researchers reported on Thursday.
The bacteria do not merely eat arsenic -- they incorporate the toxic element
directly into their DNA, the researchers said.
The finding shows just how little scientists know about the variety of life
forms on Earth, and may greatly expand where they should be looking for life on
other planets and moons, the NASA-funded team said.
"We have cracked open the door to what is possible for life elsewhere in the
universe," Felisa Wolfe-Simon of the NASA Astrobiology Institute and U.S.
Geological Survey, who led the study, told a news conference.
The study, published in the journal Science, demonstrates that one of the most
notorious poisons on Earth can also be the very stuff of life for some
creatures.
Wolfe-Simon and colleagues found the strain of Halomonadaceae in California's
Mono Lake, formed in a volcanic region and very dense in minerals, including
arsenic.
Click image to see photos of Mono Lake
Photo courtesy of Chris Adams
The lake is teeming with life, but not fish. It also contains the bacteria.
"Life is mostly composed of the elements carbon, hydrogen, nitrogen, oxygen,
sulfur and phosphorus," the researchers write in Science.
These six elements make up the nucleic acids -- the A, C, T and G of DNA -- as
well as proteins and lipids. But there is no reason in theory why other
elements should not be used. It is just that science never found anything alive
that used them.
The researchers grew microbes from the lake in water loaded with arsenic, and
only containing a little bit of phosphorus.
SCIENTISTS AMAZED
The GFAJ-1 strain of the Halomonadaceae grew when arsenic was in the water and
when phosphorus was in the water, but not when both were taken away. And it
grew even with "double whammy" of arsenic.
"It grew and it thrived and that was amazing. Nothing should have grown,"
Wolfe-Simon told a news conference.
"We know that some microbes can 'breathe' arsenic, but what we've found is a
microbe doing something new -- building parts of itself out of arsenic."
Paul Davies of NASA and Arizona State said the bacterium is not a new life
form.
"It can grow with either phosphorous or arsenic. That makes it very peculiar,
though it falls short of being some form of truly 'alien' life belonging to a
different tree of life with a separate origin," he said.
But it does suggest that astrobiologists looking for life on other planets do
not need to look only for planets with the same balance of elements as Earth
has.
"Our findings are a reminder that life-as-we-know-it could be much more
flexible than we generally assume or can imagine," said Wolfe-Simon.
"If something here on Earth can do something so unexpected, what else can life
do that we haven't seen yet? Now is the time to find out."
James Elser, an expert on phosphorus at Arizona State University, said such
bacteria may be useful for generating new biofuels that do not requite
phosphate fertilizers, treating wastewater or cleaning up toxic waste sites.
(Reporting by Maggie Fox, editing by Philip Barbara and Jackie Frank)