Discovery of an arsenic-friendly microbe refuted

— -- The discovery of an arsenic-loving microbe that NASA said would rewrite biology textbooks and offered hope of life on other planets now looks like a case study in how science corrects its mistakes, researchers report.

In findings released Sunday by the journal Science, two research teams take aim at the "arseniclife" bacteria. The microbe was announced by the journal in 2010 at a NASA news briefing as "the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic." The new findings show that was not the case.

Arsenic is a poison, and the suggestion that the bacteria called GFAJ-1 replaced phosphorus, a basic chemical constituent of biochemistry, with the toxin attracted an avalanche of critical comment online and then in journals, including Science.

The journal notes in an editorial statement that "if true, such a finding would have important implications for our understanding of life's basic requirements since all known forms of life on Earth use six elements: oxygen, carbon, hydrogen, nitrogen, phosphorus and sulfur. Arsenic is typically toxic to living organisms, but its chemical properties are similar to those of phosphorus."

The original study, funded by NASA, was led by biologist Felisa Wolfe-Simon, now of the Lawrence Berkeley (Calif.) National Laboratory, and co-authored by other federal researchers.

Wolfe-Simon and colleagues had suggested that the microbe, discovered at California's Mono Lake, "can vary the elemental composition of its basic biomolecules by substituting (arsenic) for (phosphorus)," an extraordinary claim that was essentially based on growing the bug in test tubes with the phosphorus seemingly removed. Tests suggested the bug was incorporating arsenic in places usually reserved for phosphorus, including genetic material, a result considered impossible in theory.

Theory looks to have been correct. In the new studies, one headed by Julia Vorholt of Switzerland's ETH Zurich university and the other by Rosemary Redfield of Canada's University of British Columbia, researchers tested the bug, provided by Wolfe-Simon and colleagues, and both found that while it can survive amid high arsenic concentrations, it needs some low level of phosphorus to grow. Further, they found the bug did not incorporate arsenic into its genetic chemistry.

The "new research shows that GFAJ-1 does not break the long-held rules of life," says the editorial statement by Science. The bacteria, "is likely adept at scavenging phosphate under harsh conditions, which would help to explain why it can grow even when arsenic is present within the cells," it says.

Wolfe-Simon says in response, "There is nothing in the data of these new papers that contradicts our published data." Her team hopes to submit more data on the microbe for publication within a few months, she suggests.

"The title of their paper was: 'A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus,' " says Princeton's Leonid Kruglyak, a co-author of the new research. . "We think we've shown this is not the case."

Scientific disputes over big claims first made at press conferences are nothing new, ranging from ongoing fights over 1989's claims of room-temperature batteries providing cheap energy through "cold fusion" to a 2009 "missing link" early primate fossil that now looks unrelated to humanity. But the "arseniclife" debate was the first such dispute to create an Internet hullabaloo that saw lengthy technical critiques, including a draft of the Redfield paper, available online far ahead of traditional scientific publication.

"The first report is rarely the last word, and if a finding is of interest, one needs to follow the subsequent discussion," Kruglyak says. "If a find is of high interest and importance, this usually happens fairly rapidly, and claims are either firmly verified or refuted."