Menlo Park, Calif. In a study that could rewrite biology textbooks, scientists have found the first known living organism that incorporates arsenic into the working parts of its cells. What's more, the arsenic replaces phosphorus, an element long thought essential for life. The results, based on experiments at the Stanford Synchrotron Radiation Lightsource, were published online today in Science Express.
"It seems that this particular strain of bacteria has actually evolved in a way that it can use arsenic instead of phosphorus to grow and produce life," said SSRL Staff Scientist Sam Webb, who led the research at the Department of Energy's SLAC National Accelerator Laboratory. "Given that arsenic is usually toxic, this finding is particularly surprising."
Phosphorus forms part of the chemical backbone of DNA and RNA, the spiraling structures that carry genetic instructions for life. It is also a central component of ATP, which transports the chemical energy needed for metabolism within cells. Scientists have for decades thought that life could not survive without it.
But this was not the case for a strain of Halomonadaceae bacteria called GFAJ-1, found in an eastern California lake. Colonies of these bacteria flourished, as expected, when given a steady supply of phosphorus along with other necessities; yet when researchers replaced the phosphorus with arsenic, the colony continued to grow.
This suggested to Felisa Wolfe-Simon, a NASA research fellow and geobiologist in residence with the U.S. Geological Survey, that the bacteria were using the arsenic in place of phosphorus.
"We already knew that other microbes can 'breathe' arsenic, but it seemed these bacteria could be doing something new: building parts of themselves out of arsenic," said Wolfe-Simon, the paper's lead author. "To see if that was the case, we brought samples to SSRL. I came armed with the knowledge that the bacteria were doing some
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DOE/SLAC National Accelerator Laboratory