Last December Wolfe-Simon and 11 coauthors published a paper claiming to show that bacteria isolated from an arsenic-contaminated lake could not only grow in the presence of very high concentrations of arsenic but could incorporate arsenic into their DNA in place of phosphorus. The paper was harshly criticized for its lack of controls and unjustified conclusions.
The paper has been available only as a pre-publication preprint on the Science Express site, where it has languished for the past 6 months. But today Science finally provides pre-publication copies of 8 Technical Comments on the paper, along with a formal response from the authors. The original paper, the comments and the response will all appear in the print edition of Science next week (June 3 issue).
The authors don't report any new experiments. Most of their responses take the form of 'our interpretation could be correct on this point if...'. In many cases there is indeed a small possibility that it could, but there are so many of these points of interpretation, each with only a very small probability of being correct, that I don't think anyone will find the arguments convincing.
The authors are also finally making the bacteria available so others can test them. It should be simple to find out whether arsenic is covalently incorporates into the DNA of bacteria grown with abundant arsenic but limiting phosphorus. The microbiology and molecular biology are trivial, but you'd need a chemistry collaborator to do the phosphorus and arsenic assays. (Probably a chemist would say that the chemistry is trivial but you'd need a microbiology collaborator to grow the cells and purify the DNA.)
Their responses to my Technical Comment are in some ways the most scientifically valid, as they provide information about their media and DNA purification. I'll consider these in a separate post later today.
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