Feb 16, 2012

The response to Arsenic life paper now online

From the abstract:

“Wolfe-Simon et al. reported isolation of a strain of Halomonas bacteria, GFAJ-1, which could use arsenic as a nutrient when phosphate is limiting, and which could specifically incorporate arsenic into its DNA in place of phosphorus. 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.”

The paper itself, less of a debunking and more of a failure to show reproducibility, has been submitted to Science and is awaiting peer-review. But it’s now available online for all to critique - as was every experiment the team did to reach this stage (blog). Many will see this as a huge refutation, but it’s simply the scientific process at work. Science is a slow and gradual process, and it takes many papers by many researchers across many countries to fully explore and arrive at some sort of scientific consensus no matter what the field of study is.

The original supposed arsenic strain, GFAJ-1, was isolated from the arsenic-rich sediments of California’s Mono Lake by its ability to grow in artificial medium without phosphate but with high concentrations of arsenate. The original paper by Wolfe-Simon claimed that the strain was able to use and substitute arsenic for phosphate in its DNA. Due to the simple fact that GFAJ-1 grew in medium lacking phosphate when arsenate was provided, and because significant amounts of arsenate were detected in subcellular fractions.

In this new paper, GFAJ-1 was unable to grow and proliferate. And researchers went the step further to analyse the strain’s DNA directly by chromatography. Concluding that a large portion of the arsenic seen after preliminary DNA purification was as a result of contamination from the growth medium.

It is interesting to ask the question if a paper like this, one with clear negative results, would be published by Science without the controversy surrounding the original Wolfe-Simon arsenic life paper.

The author of the original paper has declined to comment in detail until this new paper clears peer-review. She wrote in an email, “As far as we know, all the data in our paper still stand. Yet, it may take some time to accurately establish where the [arsenic] ends up.”

Indeed, we should all be prudent. As sensationalistic as the original paper was, released with much pomp and circumstance in front of a press conference, the same type of sensationalism is at work now - with a paper that we should all be reminded that has not yet cleared peer review. Reporting on it like it is fact does as much harm to the scientific process as anything else.

Written by Dr. Charles Ebikeme for The All Results Journals.

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