Arsenic-munching Germ Redefines "life As We Know It"

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    Arsenic-munching germ redefines "life as we know it"


    Getty – The 'Tufa' formations will slowly be re-submerged into the briny water where they were formed by an underwater …

    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 by David McNew/Getty Images

    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.

    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)




    This is a NASA image of the microbe GFAJ-1 grown on arsenic. The microbe is the first known life to be able to use arsenic in its DNA structure in place of phosphorous, which is used by all other known life forms. NASA

    NASA scientists have discovered a new type of bacteria that is able to substitute arsenic--a poison to most living creatures--as a biological building block, something no other known life form on Earth can do, the agency said today.

    In a press conference held at NASA's Washington D.C. headquarters, scientists announced that they had discovered a new form of bacteria, known as GFAJ-1, in California's Mono Lake that has DNA completely foreign to anything ever before found on Earth. It has the ability to substitute arsenic at the DNA level for phosphorus.

    That would distinguish it from every other form of life known to man, all of which, no matter how diverse, are based on the same six elements, phosphorus, sulfur, carbon, hydrogen, oxygen, and nitrogen. But after months in the laboratory, the bacteria that was found in Mono Lake--which is known for its unusual chemistry, including very high levels of salinity, alkalinity, and arsenic--was found to have substituted arsenic atoms for phosphorous atoms in its cells.

    "We've discovered an organism that can substitute one element for another," said Felisa Wolfe-Simon, a NASA astrobiology research fellow at the U.S. Geological Survey in Menlo Park, Calif. "We've cracked open the door to what's possible for life elsewhere in the universe."

    Although there had been speculation that NASA's announcement would revolve around life--perhaps bacteria--found elsewhere, such as Mars, the news does keep us here on Earth.

    But Wolfe-Simon said that by discovering a microbe that has this adaptable DNA, it forces scientists to question what they've long held as true--that all life was based on the same six components.

    "The newly discovered microbe, strain GFAJ-1, is a member of a common group of bacteria, the Gammaproteobacteria," NASA wrote in a release. "In the laboratory, the researchers successfully grew microbes from the lake on a diet that was very lean on phosphorus, but included generous helpings of arsenic. When researchers removed the phosphorus and replaced it with arsenic, the microbes continued to grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new GFAJ-1 cells."

    NASA feels that this discovery is important because it will help scientists with many areas of future research, such as the "study of Earth's evolution, organic chemistry, biogeochemical cycles, disease mitigation, and Earth system research. These findings also will open up new frontiers in microbiology and other areas of research."


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