First there was the wild speculation about the discovery of extraterrestrial life. Then came widespread, sometimes misguided, coverage of the real news: discovery of a bacterium than can substitute arsenic for phosphorus, one six elements considered essential for life (which may, perhaps, expand the scope of humanity’s search for life beyond this planet).

Now comes the third installment in the commotion-filled saga: widespread criticism of the paper detailing the discovery, published last Thursday in Science, and an apparent snubbing of the media by the paper’s authors and NASA (which helped fund the research), who rebuffed journalists’ requests for a response to the criticism.

The latest round of controversy began on Saturday when University of British Columbia microbiologist Rosie Redfield penned a scathing critique of the paper, “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorous,” on her personal blog. One of the key findings of the study was that the bacterium, discovered in Mono Lake and cultured in a lab, incorporated arsenic into its DNA. But Redfield argued that the paper didn’t “present ANY convincing evidence” that that actually happened (for DNA or any of the bacterium’s other biological molecules).

Redfield criticized a number of the research team’s methodologies. For instance, she argued that scientists did not correctly purify the DNA in order to remove any arsenic that might simply have been sticking to the DNA. She also said that the bacterium was grown in an environment with enough phosphorous (even at such a depleted level) to account for the observed bacterial growth, which was attributed to arsenic. The “bottom line,” Redfield wrote, was “lots of flim-flam, but very little reliable information.”

Redfield’s post immediately caught on in the blogosphere. Science reporter David Dobbs highlighted it on his Wired Science blog, Neuron Culture, observing that although he wasn’t familiar with Redfield, “her opinion was quickly seconded in the blog’s comments and on Twitter by many sharp scientists.”

Things got even more interesting when NASA rebuffed the Canadian Broadcasting Corporation after it sought comment on Redfield’s critique. According to its article, published Monday evening:

When NASA spokesman Dwayne Brown was asked about public criticisms of the paper in the blogosphere, he noted that the article was peer-reviewed and published in one of the most prestigious scientific journals. He added that [Felisa] Wolfe-Simon [the paper’s lead author] will not be responding to individual criticisms, as the agency doesn’t feel it is appropriate to debate the science using the media and bloggers. Instead, it believes that should be done in scientific publications.

“Any discourse will have to be peer-reviewed in the same manner as our paper was, and go through a vetting process so that all discussion is properly moderated,” wrote Felisa Wolfe-Simon of the NASA Astrobiology Institute. “The items you are presenting do not represent the proper way to engage in a scientific discourse and we will not respond in this manner.”

[Update, Dec. 8: Despite her initial reluctance to respond to the criticism, Wolfe-Simon posted the following comment on her blog on Wednesday:

“My research team and I are aware that our peer-reviewed Science article has generated some technical questions and challenges from within the scientific community. Questions raised so far have been consistent with the range of issues outlined by journalist Elizabeth Pennisi in her Science news article, which was published along with our research. For instance, other scientists have asked whether the bacteria had truly incorporated arsenic into their DNA, and whether the microbes had completely stopped consuming phosphorus. Our manuscript was thoroughly reviewed and accepted for publication by Science; we presented our data and results and drew our conclusions based on what we showed. But we welcome lively debate since we recognize that scholarly discourse moves science forward. We’ve been concerned that some conclusions have been drawn based on claims not made in our paper. In response, it’s our understanding that Science is in the process of making our article freely available to the public for the next two weeks to ensure that all researchers have full access to the findings. We invite others to read the paper and submit any responses to Science for review so that we can officially respond. Meanwhile, we are preparing a list of “frequently asked questions” to help promote general understanding of our work.”]

That irked Dobbs, who penned a second post at Neuron Culture, arguing that:

This is a call to pre-Enlightenment thinking. Brown is telling us to judge utterances not by their content, not even by the integrity, reputation, and experience of the individuals who deliver them, but by whether they’re delivered from the proper place in the proper building — in pre-Enlightenment days, the Church of Rome; in Brown’s post-arsenic days, the Church of the Peer-reviewed Journal.

It’s an extraordinary dismissal. Rosie Redfield is a full-bore member of the academy and a researcher in the field under question. She is — to extend the metaphor — a priest. But though Redfield wears the proper robes, Brown wants to dismiss her because she’s not standing on the proper altar.

Science journalist Carl Zimmer got a similar reaction when he decided to check up on the online criticisms from Redfield and others. On Monday, he contacted a dozen experts for an analysis published by Slate. “Almost unanimously,” he found, “they think the NASA scientists have failed to make their case.”

When Zimmer got in touch with the two of those scientists, however, they “politely declined” to respond to the criticism:

“We cannot indiscriminately wade into a media forum for debate at this time,” declared senior author Ronald Oremland of the U.S. Geological Survey. “If we are wrong, then other scientists should be motivated to reproduce our findings. If we are right (and I am strongly convinced that we are) our competitors will agree and help to advance our understanding of this phenomenon. I am eager for them to do so.”

The apparent snub raised the hackles of scientists and bloggers alike. Zimmer reported that despite Redfield’s low opinion of the paper published in Science, “she thinks it’s fine for the NASA scientists to hold off responding to their critics,” and that she is working on a formal letter to Science detailing her objections [Update, Dec. 8: Redfield has posted her letter to Science on her blog]. But, Zimmer continued, UC Davis microbiologist Jonathan Eisen won’t “let the scientists off so easily”:

“If they say they will not address the responses except in journals, that is absurd,” he said. “They carried out science by press release and press conference. Whether they were right or not in their claims, they are now hypocritical if they say that the only response should be in the scientific literature.”

Reactions were similar elsewhere in the blogosphere. On his Code for Life blog, computational biologist Grant Jacobs wrote:

I can sympathize with wanting the science to be discussed by people informed on the science, and the traditional channel is research journals. I can sympathize that replying in person, individually one-on-one, to each criticism would be onerous and not practical given how much of it there is.

But you can’t realistically ask scientists not to discuss this work publicly, in their coffee rooms, by the water cooler, at the café or other forums. That includes if media ask them for an opinion, or on their blogs.

The Guardian’s recently created “Science Story Tracker” has done an excellent job of cataloguing the evolution of this controversial story from day one, when people were still speculating about the discovery of aliens. (The site has tracked the unfolding of four stories since it was launched in June, and this latest effort really exemplifies the value of this unique blog.)

How many more installments will we see? Perhaps only one, Zimmer guessed in his post for Slate.

“Critics say that a few straightforward tests on the bacteria would show whether they really do have arsenic-based DNA once and for all,” he reported. “And the NASA scientists say they’re ready to hand out GFAJ-1 to researchers who want to study it. This controversy may be burning brightly at the moment, but it probably won’t burn for long.”

Curtis Brainard is the editor of The Observatory, CJR's online critique of science and environment reporting. Follow him on Twitter @cbrainard.