Debate over arsenic-based life enters a new chapter

Science is messy. And the bigger the claim, the more intense the criticism.

So it went in December, when a NASA-funded researcher announced a discovery with far-reaching implications: a bizarre microbe from a California lake that incorporated the toxic element arsenic into its very DNA.

The existence of an arsenic-based life form would radically rewrite the rules of biology. All life as we know it requires just six elements to exist — and never arsenic.

The announcement — pumped by NASA as having implications for “extraterrestrial life” — drew broad attacks from all points of the scientific establishment.

Now, nearly six months later, the prestigious journal that triggered the controversy by publishing the researcher’s findings has returned to the subject, compiling detailed criticisms of the work — and her response.

The upshot: Felisa Wolfe-Simon, the researcher who sparked the scientific firestorm, is not backing down from the scientific fusillade — at least not much. In a defense that Science posted Friday morning to its Web site, Wolfe-Simon concedes some technical points. But she and her colleagues “maintain that our interpretation [of arsenic-based life] is viable.”

“What we’re doing is saying that a lot more work needs to be done,” Wolfe-Simon said in an interview Friday. “We need to get back in there and collect more evidence.”

She maintains that her work represents “a potential fundamental change in one of the tenets of biochemistry.”

Dealing with the intense criticism was a “challenge,” said Wolfe-Simon, 34.

But in addition to drawing vocal critics, the finding has attracted new collaborators, too, she said, who are now rushing to search for arsenic in the molecules of life inside the bacteria. The intense attention “will really help move science forward at a rapid pace,” she said.

Wolfe-Simon added that she will share results of new experiments underway “in due time.”

Science magazine limited the response published Friday to addressing specific criticisms of the original work and did not allow her to present any new evidence, she said.

Wolfe-Simon, who works at the NASA Astrobiology Institute in Menlo Park, Calif., sparked the debate when she and her colleagues reported in Science that a microbe isolated from the arsenic-laden Mono Lake thrived on one of Agatha Christie’s favorite poisons.

Normally, phosphorus forms the backbone of all DNA molecules, the winding spiral rulebooks for building all life on Earth, be it a microbe, an elephant or us. Wolfe-Simon argued that the microbe from Mono Lake had somehow dumped that element in favor of arsenic.

If such a radical life form really exists, it would be the vanguard member of a “shadow biosphere.” A whole shadow world of arsenic-based life might be lurking just out of view — something alien to science and yet earthbound all the same.

A lot of distinguished academics simply didn’t believe it, while others bristled at the torrent of publicity. The assertions ranged widely: Wolfe-Simon’s methods were sloppy, her conclusions an overreach. Science magazine had failed to vet the research properly. NASA had hyped the finding.

One of Wolfe-Simon’s loudest critics, who accused her in December of sloppy lab work, is zoologist Rosie Redfield of the University of British Columbia. In the batch of eight critiques released Friday morning, Redfield flatly states that Wolfe-Simon’s dishes of bacteria were contaminated and that the scientist failed to properly purify the bacteria’s DNA .

Another critique, from Steve Benner at the Foundation for Applied Molecular Evolution, points out that the arsenic compounds supposedly employed by the bizarre bacteria would fall apart in DNA — not hold together as required.

A third attack highlights other microbes that can live on tiny amounts of phosphorus, and argues that Wolfe-Simon’s bacteria were probably doing the same.

Although on occasion Science publishes technical critiques — the scientific equivalent of saying, “I don’t believe you” — releasing eight such attacks is extraordinary. It was driven, in turn, by the extraordinary nature of the original claim, the journal said in a statement.

“The fact that we received so much feedback to the Wolfe-Simon paper suggests to us that science is proceeding as it should,” the statement read.

Further, Wolfe-Simon has provided samples of the supposedly arsenic-loving microbes to “four or five” independent scientists, she said, who are now trying to prove her wrong — or maybe just show that she was right.

As with any extraordinary scientific claim, expect the battle to rage for years. Grab some popcorn if you’re into this kind of thing — salt only, please, no arsenic.

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