  A strain of Halomonas bacteria, GFAJ-1, has been reported to be able to use
arsenate as a nutrient when phosphate is limiting, and to specifically
incorporate arsenic into its DNA in place of phosphorus. However, we have found
that arsenate does not contribute to growth of GFAJ-1 when phosphate is
limiting and that DNA purified from cells grown with limiting phosphate and
abundant arsenate does not exhibit the spontaneous hydrolysis expected of
arsenate ester bonds. Furthermore, mass spectrometry showed that this DNA
contains only trace amounts of free arsenate and no detectable covalently bound
arsenate.
