You certainly remember the allegedly revolutionary discovery of a bacterium using arsenic instead of phosphate to build its nucleic acids. Arsenic is a poison, and phosphate is mandatory for life. Thus, this alien, “the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic” as presented during the NASA HQs press conference, was supposed to be an alien constituting a paradigm shift, etc. — you remember the hype. The alien that wasn’t one as I already summed up critics shortly after the paper was published (ici en français). The story received an incredible media coverage as well as a huge number of comments from other fellow scientists. A few months after the paper was published in Science, follow-up studies revealed the bacterium does require phosphate — even though in small amounts — to be able to grow and sustain life.

Two years after, the arsenic life story is in the spotlights again: this sounds quite normal, as “#arseniclife changed science.” USA Today’s Dan Vergano published the reviewers comments with answers from the authors earlier today which is quite a twist in the drama. A few excerpts of the most astounding kind (imho):

The methods applied are straightforward. The most surprising and acknowledgeable aspect of the work is its simple approach. […] The results are exceptional. (Reviewer 1)

The authors provide many lines of evidence to proove their point that the isolated novel bacterium (at least to some extent) can replace phosphate by arsenic in its biomolecules. It’s a pleasure to get a well-concieved and carrled-out study to review. (Reviewer 2)

Reviewing this paper was a rare pleasure. It is clearly-written and well-reasoned. The authors chose the right moment, designed the right experiments, obtained solid data supporting the conclusion that GFAJ-1 uses As in place of P. They use appropriate caution in interpreting results. I think the paper is just about publishable as is; my comments for revision are below. Great job! I look forward to seeing follow-up work in the future. (Reviewer 3)

Honestly? My favourite one is Reviewer 3. Would make a great fanclub founder.

Interestingly, reviewer 1 suggested the title to be changed to the current one the emphasis being on “can grow”. I’m curious to know what the initial title was. Furthermore, there were no dismissing reviews. I mean, it is perfectly normal to ask for clarifications, etc., even providing grammar fixes or improving figure captions. Yet, fact is that the reviews were quite short and all of them said the paper had to be published, which well… is just pretty rare. This is not a reason of dismissing them out of jealousy. Such a collection of review comments and the answers provided is somewhat puzzling if one considers the focus of the study: it is the alleged arsenic bug physiology. But explanations and data about it are barely provided, one example among others (from Reviewer 2):

5) In order to demonstrate and quantify the replacement of P by As, I recommend isolating DNA/RNA and determining the element ratio of C, N, As to demonstrate and quantify to which extent P was replaced by As.

We have included a new figure (new Figure 2) that addresses this issue. Here we present evidence of extracted gel purified genomic DNA from +As/-P cells that contains As as compared to -As/+P cells. Although our data suggests that it still includes some P, we argue that this is in agreement with the other evidence we have, that is that the cells are scavenging some very small quantity of P. We also argue that it is not enough for cellular maintenance.

I leave you reading the whole document, which is quite short. Among the reactions on Twitter (follow the hashtag #arseniclife), this one is very interesting:

@leonidkruglyak Choice of reviewers puzzling. I contacted a dozen of the best experts I could think of. None were reviewers #arseniclife

— carlzimmer (@carlzimmer) 2 février 2013

A great read that quotes an important number of people discussing the study and its reviews: “Glowing reviews on ‘arseniclife’ spurred NASA’s embrace”

Loads of bits were spilled, but I particularly remember this post from David Dobbs where he discusses the lead author’s fate, intimately tied to the #arseniclife story. Academentia huh…