Before revision:  We have found that arsenate is not needed for growth of GFAJ-1 when phosphate is limiting . Additionally, we used mass spectrometry to show that DNA purified from cells grown with limiting phosphate and abundant arsenate does not contain detectable arsenate.
After revision:  We have found that arsenate is not needed for growth of GFAJ-1 when phosphate is limiting and that DNA purified from cells grown with limiting phosphate and abundant arsenate does not contain detectable arsenate.