Many biologists were saying from the start that Felisa Wolfe-Simon and colleagues never supported their 2010 claim that they’d discovered a life form that could substitute arsenic for phosphorus in its DNA and other biomolecules.
Since then, several published papers have refuted that claim, which was published in Science and touted in a NASA press conference that led to worldwide headlines about rewriting textbooks and evidence for a so-called shadow biosphere. If there was an award for the all time most extreme example of NASA hype, that press conference should win.
The latest paper appeared in this week’s issue of Nature, and was picked up by a number of science writers. Nature news writer Daniel Cressey covered it here. Carmen Drahl of Chemical and Engineering News covered the latest here.
Jesse Emspak of weighed in here at LiveScience, and did the right thing by trying to contact Felisa Wolfe-Simon, who was lead author on the original paper. She replied with this semi-coherent email:
For her part, Wolfe-Simon, via email, said the new research, "represents the kind of careful and interesting studies that aid the community. They have helped us understand molecular level discrimination between arsenate and phosphate in GFAJ-1 and other microbes." She added that her own work spoke to the presence of arsenate in the cells, and that "questions are as to how and where."
Carl Zimmer has covered the issue repeatedly for The Loom. In Slate, he wrote one of the first skeptical pieces to appear in the popular media. In this post on today’s news, he explained the biochemical tricks the organisms apparently use to survive on very little phosphorus. He concluded that while the bacteria are just part of plain old ordinary life, they are still interesting.
Finding alien life on Earth would have been grand. But seeing how life as we know it manages to adapt to our planet’s extremes is also a pleasure. And it’s a good place for the story of arsenic life to stop: at the point where new science begins.
There were really two problems with the original claims – a scientific problem and a hype problem. When I covered the initial news in 2010 it wasn’t hard to find skeptics. It soon became apparent that the more expertise scientists had in the relevant fields, the less they thought of the paper.
The claims "do not follow from their results," said Simon Silver, a University of Illinois microbiologist who specializes in heavy-metal resistance in bacteria. "This conclusion is not merited from what they did and measured and I think it most likely is a mistake and should never have been claimed or published."
The second problem was the way the results were spun by NASA and hyped by reporters. Some reporters seemed wowed that the bacteria live in “poison”. Biologists were not so impressed. Here’s what Gerald Joyce and Willem Stemmer had to say:
In 1997, scientists published a paper in Nature Biotechnology showing they could grow E. coli in even more concentrated arsenic than Wolfe-Simon used, Scripps' Joyce said. "It's relatively straightforward to get something that lives in a high concentration of arsenic," added Willem Stemmer, who did that study and is now CEO of the California biotech Amunix.
Even if the scientists had shown that a DNA molecule had incorporated some arsenic atoms, there was no possible justification for the FSW’s vague hints that her findings said anything about a so-called shadow biosphere. That term refers to the speculative idea that some separate origin of life led to an invisible or very well-hidden biosphere right here on Earth.
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