Critics take aim at NASA 'arsenic life' study

Eight articles questioning a controversial study claiming that some bacteria can use the normally toxic substance arsenic to build DNA have been published in the journal Science.

The study, published last December in Science, was led by NASA scientist Felisa Wolfe-Simon and claimed that bacteria from a lake in California were able to substitute arsenic for phosphorus, normally an essential ingredient in DNA, fats and proteins.

University of British Columbia zoology professor Rosie Redfield was one of more than a dozen scientists from around the world who challenged those findings and whose comments were published Friday.

Science also published a response from Wolfe-Simon and her co-authors, who wrote that they welcomed the opportunity.

But they said they maintained that their interpretation "based on multiple congruent lines of evidence, is viable."

The researchers also said they will make the strain of bacteria they studied available for other scientists to test.

Wolfe-Simon and her colleagues described a new strain of Halomonadaceae bacteria found in Mono Lake, Calif., that seemed to be able to use arsenic — an element that is usually toxic to living things — instead of phosphorus.

"If true, this finding would raise important questions about life's basic requirements, since only six elements — carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorus — make up the bulk of living matter," said Science in a statement published alongside the criticisms of the study.

"As would be expected after a study with such broad implications is published, scientists have asked comparably challenging questions."

The journal's editor-in-chief, Bruce Alberts, acknowledged in a statement that the article was "the subject of extensive discussion and criticism."

He added that the editors hope the series of new articles will "allow readers to better assess the research article's original claims and the criticisms of them."

Not 'final word': editors

Alberts and the other editors noted that they don't consider the paper to be "the final word" on the subject but something that provides "further opportunities for research and interpretation."

After Wolfe-Simon's article was published, other scientists began criticizing the study's techniques and questioning the results and their interpretation on the internet. Redfield published a lengthy criticism on her blog, RRResearch, which generated tens of thousands of hits and dozens of comments from other scientists within a few days.

At that time, NASA said Wolfe-Simon would not be responding to those criticisms, as the U.S. space agency did not feel it was appropriate to debate the science using media and blogs. Instead, it said, the debate should occur in scientific publications.

On Friday, Redfield posted on her blog that Wolfe-Simon's and her colleagues' responses to her criticisms were "in some ways the most scientifically valid" because they provide more information about what precautions were taken to avoid contamination in the experiment.

However, she was largely critical of the researchers' statement.

"Most of their responses take the form of 'our interpretation could be correct on this point if...'," she wrote.

"In many cases, there is, indeed, a small possibility that it could, but there are so many of these points of interpretation, each with only a very small probability of being correct, that I don't think anyone will find the arguments convincing."