“I think we have now very solid evidence that the metabolism of GFAJ-1 is as dependent on phosphorus, as are all other known forms of organic life,” says Vorholt. “These very robust and very well-adapted microbes appear to be able to efficiently extract nutrients from their extremely phosphorus-poor environments.”
The samples that Wolfe-Simon’s team had used for their original experiments apparently contained larger concentrations of phosphorus than was first thought, Vorholt adds.
In a statement, Science said: “The new research shows that GFAJ-1 does not break the long-held rules of life, contrary to how Wolfe-Simon had interpreted her group’s data.”
"The original GFAJ-1 paper emphasized tolerance to arsenic, but suggested the cells required phosphorus, as seen in these two new papers," says Wolfe-Simon. "However, our data implied that a very small amount of arsenate may be incorporated into cells and biomolecules, helping cells to survive in environments of high arsenate and very low phosphate. Such low amounts of arsenic incorporation may be challenging to find and unstable once cells are opened."
The story of GFAJ-1 is far from over, she adds. "The key questions are: how do these cells thrive in lethal concentrations of arsenic? And where does the arsenic go?"