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Remember the arsenic eating bacteria? Paper in Science refutes claim

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Regular readers may remember Rosie Redfield, the Canadian scientist who couldn’t reproduce the results of a NASA-backed study claiming that some bacteria can use arsenic in place of phosphorus? The study authors wouldn’t comment, and told her to go get published somewhere. Well …

In “‘Arsenic bacteria’: If you hadn’t nailed ‘im to the perch ‘e’d be pushing up the daisies” (The Curious Wafefunction, June 4, 2012), Ashutosh (Ash) Jogalekar reports,

Rosie Redfield (who blogs on this network) has just published an official, careful and decisive rebuttal to the “arsenic bacteria” fiasco in collaboration with a group at Princeton. The paper which will appear in Science is under embargo for now, but there is a copy available at that bastion of free publication arXiv. Readers may remember Redfield as the scientist who offered the most meticulous preliminary criticism of the original paper by Felisa Wolfe-Simon and others. Wolfe-Simon and the rest of the arsenic group refused to engage in debate with Redfield and other critics at the time, citing the “non-official” nature of the offered criticism and asking for publication in a more formal venue. Looks like they finally got their wish.

The abstract could not be clearer:

“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.”

It’s a fairly short paper but there are many observations in it which quite directly contradict the earlier results. The strain of bacteria that was claimed to grow only when arsenic was added to the medium was found to not grow at all. In fact it did not budge even when some phosphate was added, growing only after the addition of other nutrients.

No wonder reproducibility is getting all the buzz.

See also: Big news in peer review: The Reproducibility Project (= the bunk watch)

Hat tip: Pos-Darwinista

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