Reacción a "‘Science’ retracts controversial article on bacteria that used arsenic to grow, published in 2010"

The controversy surrounding this article has been going on for more than fifteen years, since it began during the review process prior to publication. When the original article was published, many people expressed doubts and the work, which had a major media impact as it seemed to demonstrate that exotic life using arsenic alongside phosphorus was possible, was subjected to harsh scientific criticism.

The basis of the criticism was that the authors did not really demonstrate that arsenic could replace phosphorus in key molecules such as nucleic acids, and that ‘arsenic-based life’ was not possible. Rather, what they saw were bacteria that were particularly resistant to arsenic-rich environments, which would be toxic to other organisms, but not the incorporation of this element as a substitute for phosphorus. The doubt was reasonable: arsenic is similar to phosphorus in some of its chemical forms, particularly arsenates, which are very similar to phosphates, so, on paper, arsenic could perhaps act as a ‘substitute’ for phosphorus under certain conditions.

In fact, we conducted experiments on how arsenic could accompany or affect prebiotic phosphorylation, i.e., the incorporation of phosphate into organic molecules in conditions prior to the origin of life, and we observed that not only did arsenic not replace or accompany phosphorus, but its presence could inhibit phosphorylation. In other words, arsenic could have been toxic even to the origin of life itself.

We always thought that arsenic-based life was chemically impossible and used this article as an example of bad science; I have even used it in class as a case study for students, in exercises where they had to evaluate why the work reached incorrect conclusions.

And now, finally, the article has been retracted, a decision with which I do not agree. Clearly, there was no misconduct or lack of professionalism on the part of the authors of the original article; it was simply a matter of errors in the interpretation and discussion of the experimental data, which is common in science and is not a bad thing; on the contrary, it shows that the discussion of scientific results works and that science moves forward, leaving behind erroneous ideas or incorrect interpretations.

The truth is that the retraction is welcomed by some (I have colleagues who think it was long overdue) and disputed by others. The retraction is as controversial as the article itself and has hurt NASA quite a bit, where they have fought hard for a long time to avoid it. That is why I think (unlike many of my colleagues) that the retraction is excessive, as it carries a negative reputational burden that is perhaps unfair.