Arsenic-DNA Bacteria Disputed

In 2010, the journal Science published a paper by NASA Astrobiologist Felisa Wolfe-Simon and her team, which describes a rare extremophile found in Lake Mono, California. This bacteria, labeled GFAJ-1, appeared to be able to switch out the life essential element phosphorus for that of the chemically similar, but poisonous element arsenic. The implication was that if life on Earth could be persuaded to take in and use arsenic, which is very poisonous, then the possibilities for extraterrestrial life can be broadened to include arsenic-using organisms. it was a finding that immediately caused a stir in the scientific community. Now, two papers out in Science refute this arsenic-for-phosphorous claim.

Mono Lake is a promising place to look for extremophilic behavior. The waters there have high levels of arsenic and a productive ecosystem based on brine shrimp that thrives despite arsenic's poisonous nature. The temptation to see just how well-adjusted that ecosystem is to elemental arsenic is understandable. Felisa Wolfe-Simon led a research team to investigate this possibility and claimed to have found the bacteria GFAJ-1 substituting phosphorous for arsenic. The claim, more specifically, indicated that the bacteria was able to incorporate small amounts of arsenic in place of phosphorous in the bacteria's DNA and do so successfully, making it the first known lifeform on Earth to do this. The results were published in Science in December of 2010 and quickly caused consternation among some in the scientific community.

Two papers out now in the journal Science refute this claim, each saying that the evidence is lacking. Rosemary Redfield of the University of British Columbia in Canada found no evidence that GFAJ-1 was taking in and using arsenic in its DNA, saying "mass spectrometry shows that this DNA contains only trace amounts of free arsenate and no detectable covalently-bound arsenate" (ABC News). Tobias Erb of the second paper concludes similarly that "GFAJ-1 is an arsenate-resistant, but still a phosphate dependent bacterium" (ABC News).

Despite these new objections to the validity of Wolfe'Simon's claim, it seems that Felisa Wolfe-Simon is sticking to her guns. As ABC News reports it, Wolfe-Simon stated in an email "There is nothing in the data of these new papers that contradicts our published data, which is also consistent with our current results. Our work continues to build upon our finding of extreme resistance to arsenate toxicity and the unexpected uptake of arsenate in GFAJ-1 cells in the absence of added phosphate."

The overall conclusion to GFAJ-1's arsenic drama lies int he future still. Science, which is the systematic investigation of the truth, must go through these phases of contradiction. However, it seems that GFAJ-1's powers involving arsenic may have been exaggerated. The prospect of organisms with arsenic-laced DNA on Earth or elsewhere in the galaxy seems exotic and still holds interesting implications for how life can express itself. perhaps one day we will see such a thing.