Comment on “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus”

Wolfe-Simon et al. (Research Articles, 3 June 2011, p. 1163; published online 2 December 2010) reported the discovery of an unusual bacterium, strain GFAJ-1, that can grow in the presence of high concentrations of arsenate. The authors’ contention, however, that this microbe can appreciably vary the elemental composition of its fundamental biomolecules by substituting arsenic for phosphorus appears premature based on the data presented.