Arsenic-Tolerant GFAJ-1 Bacterium Still Needs Phosphorous

18 months after the controversy started, it’s become official that the arsenic-tolerant bacterium, GFAJ-1, found in California’s Mono Lake, cannot live without phosphorous. It was reported in 2010 by a group led by Felisa Wolfe-Simon, a microbiologist, now working at the Lawrence Berkeley National Laboratory, in the journal Science that the Halomonadaceae bacterium GFAJ-1 could include some atoms of arsenic instead of phosphorous in hits crucial biochemicals.

Rosie Redfield, a microbiologist at the University of British Columbia, in Vancouver, Canada, tested these claims and now has reported in the journal Science that although GFAJ-1 tolerates arsenic, it still depends on phosphorous, effectively refuting Wolfe-Simon’s claims.

GFAJ-1 was discovered thriving in the arsenic-rich sediment of Mono Lake, in California. While arsenic has some chemical similarities to phosphorous, it’s toxic to life. The suggestion that GFAJ-1 had phosphorous in its DNA triggered a plethora of questions and criticisms. Redfield was also unable to reproduce Wolfe-Simon’s results in the laboratory. A second paper by Julia Vorholt, a microbiologist at the Federal Institute of Technology in Zürich, Switzerland, was published in Science on July 8th.

GFAJ-1’s DNA contained no detectable amounts of arsenic, as well as arsenic compounds. In the second paper, Vorholt reported that the bacterium cannot grow in a phosphorous-free environment. It can grow in low-phosphate conditions, and in the presence of arsenate. GFAJ-1 is arsenic-resistant, but still phosphorous-dependent.

There are still open questions as to how these cells thrive in lethal concentrations of arsenic and where the arsenic goes.

[via Nature]

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