Minding the As and P: Can Arsenic Substitute for Phosphorus or Not?

Image of GFAJ-1 grown on arsenic. Image Credit: Jodi Switzer Blum

Back in December 2010, there was a press conference held by NASA to announce the discovery of a bacterium found in a high salt, high pH lake with high concentrations of arsenic that seemed to have substituted arsenic for phosphorus in the bacterium’s biomolecules. This set off a wave of response in the blogosphere regarding what Felisa Wolfe-Simon and her team did nor did not do to confirm arsenic was incorporated into DNA molecules. Controversy ranged from the ability of arsenic to form a stable compound to the types of experiments conducted to confirm incorporation of arsenic into molecules like DNA.

Wolfe-Simon et al. stated they would address all critiques of the Science paper if the critiques were also subject to peer review like their paper titled “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus”. On May 27, Science published eight Letters to the Editor and the Wolfe-Simon et al. response to the critical comments. Continue reading

Six Required Elements for Life: C, N, O, S, H, and P. Well, maybe not P.

Image of GFAJ-1 grown on arsenic. Image Credit: Jodi Switzer Blum

According to James Elser, professor at Arizona State University, the one thing he could always count on telling his students was that “Every living thing uses phosphorus to build its DNA.” After Thurday’s announcement by NASA astrobiologist Felisa Wolfe-Simon, he will probably be rewriting his lectures.

At a NASA press conference at 1:00 pm, December 2, 2010, Dr. Wolfe-Simon described work by her team to identify organisms that could make interesting elemental substitutions in biomolecules. Specifically the team looked at Mono Lake, located in California, USA in the Eastern Sierra. Mono Lake is representative of an extreme environment because it registers a pH of 10, is three times more salty than sea water, and contains a great deal of arsenic (average = 200µM), a normally toxic element.

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