RENEE MONTAGNE, host:
This is Morning Edition from NPR News. I'm Renee Montagne.
Scientists made headlines about six months ago with a paper describing a mysterious microbe. It appeared to substitute the poison arsenic for one of the elements considered essential for life. A lot of scientists were skeptical at the time. And now, as NPR's Jon Hamilton reports, eight have published formal critiques of that paper.
JON HAMILTON: What really got the media's attention back then was a massive, highly publicized press conference hosted by NASA. Felisa Wolfe-Simon, a NASA scientist and the paper's lead author, made a dramatic claim:
Dr. FELISA WOLFE-SIMON (Microbial Geobiologist, NASA): This is an organism that has solved the challenge of being alive in a unique way.
HAMILTON: Wolfe-Simon's paper described a bacterium found in California's Mono Lake. The creature seemed to thrive using arsenic in place of phosphorous, which is one of the six elements commonly found in living organisms.
It was an extraordinary idea. Right here on earth there was a form of life that followed different rules. And if that were true, it increased the likelihood that life could exist on other planets too. But scientists like Patricia Foster of Indiana University say the hype got ahead of the science.
Dr. PATRICIA FOSTER (Biology, Indiana University, Bloomington): I was skeptical right from the start because it just seems such an improbable thing. Plus, I was put off by all the press that surrounded it, you know, that sort of immediately gets your attention, saying wait a minute, why are they hyping this up so much.
HAMILTON: Foster's detailed critique appears in the online edition of the journal Science, which also published the original paper.
Foster doesn't question the integrity of Wolfe-Simon and her team, only their conclusions. She believes the team did find a remarkable creature that can thrive on lots of arsenic and very little phosphorous. But that doesn't show it could get by without any phosphorous at all. Foster says Wolfe-Simon should have offered a stronger case before making that kind of extraordinary claim.
Dr. FOSTER: It's perfectly valid to say that you've got to give me more evidence to back that up because there's no precedent.
HAMILTON: Other criticisms come from chemists. Steven Benner says he's not surprised because chemists see the world in a very different way than biologists like Wolfe-Simon. Benner is both a chemist and an astrobiologist. He who works at the Foundation for Applied Molecular Evolution and the Westheimer Institute for Science in Gainesville, Florida.
And Benner says the idea that an organism could be lapping up arsenic and incorporating it into the structure of its DNA wouldn't necessarily be ruled out by a biologist.
Dr. STEVEN BENNER (Astrobiologist, Foundation for Applied Molecular Evolution): On the other side, the chemists are basically saying this hypothesis is at such odds with what we know about chemistry it's not even worth considering.
HAMILTON: Benner says the rules of chemistry suggest that any DNA molecule with arsenic in place of phosphorous should fall apart in water in a matter of minutes. But the biologist Wolfe-Simon argues that her microbe seems somehow able to get around that problem.
So I asked Benner where all this leaves us.
Dr. BENNER: Well it leaves you in a interdisciplinary discussion - you might call it a fight - where the standards of proof and the sort of the ground rules for having that discussion are not settled on in the first place.
HAMILTON: Wolfe-Simon says the critiques haven't changed her mind.
Dr. WOLFE-SIMON: We really maintain that our interpretation of arsenic substitution is still viable and valid.
HAMILTON: And she says one result of all the debate is that she's been getting lots of offers from scientists who want to help figure this thing out. So she says it shouldn't be long before we all know a lot more about her mysterious microbe.
Jon Hamilton, NPR News.
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