Arsenic-Based Life Claims Knocked Down In One-Two Punch

The 2010 discovery of a bacterium that chowed down on arsenic and challenged fundamental assumptions about the building blocks of life was actually a mistake, researchers said Sunday.

Two teams of scientists published papers in the journal Science challenging a previous paper in the same journal from former NASA scientist Felisa Wolfe-Simon, currently working at the Lawrence Berkeley National Laboratory. Wolfe-Simon and her team said they'd found that a strain of bacteria called GFAJ-1 could, in a pinch, subsist on arsenic instead of phosphorus, and could also integrate arsenic into the backbone of its DNA.

The find challenged fundamental assumptions about biology, since all living things need phosphorus to survive. If life could use other elements instead, though, that would greatly expand possibilities for life on other worlds. NASA trumpeted the discovery as one that will impact the search for evidence of extraterrestrial life in a news conference.

But Wolfe-Simon's paper has faced criticism since it first went to press.

I don't know whether the authors are just bad scientists or whether they're unscrupulously pushing NASA's 'There's life in outer space!' agenda, University of British Columbia microbiologist Rosie Redfield wrote as part of an extensive, scathing critique of the original paper in December 2010.

In the newest research, both teams - one led by Princeton scientist Marshall L. Reaves and including Redfield, and another group from Switzerland - found that they were unable to replicate Wolfe-Simon's results. GFAJ-1 failed to grow in an arsenic-containing medium when phosphorus was completely taken away, and both teams could not find any evidence that the bacterium was incorporating arsenic in its DNA.

Wolfe-Simon said the new research does not contradict her published data and that her team expects to submit new evidence within the next few months, according to USA Today.

But Science editors seem to be siding with the skeptics. The new research shows that GFAJ-1 does not break the long-held rules of life, the journal said in an editorial statement obtained by USA Today. GFAJ-1 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.

SOURCES: Reaves et al. Absence of Detectable Arsenate in DNA from Arsenate-Grown GFAJ-1 Cells. Science published ahead of print 8 July 2012; Erb et al. GFAJ-1 Is an Arsenate-Resistant, Phosphate-Dependent Organism. Science published ahead of print 8 July 2012.