A year and a half after one team of researchers claimed they had bred a type of bacteria that could live on arsenic, suggesting that life is weirder than we imagine, two other teams have found that the microbe really doesn't do anything with the arsenic after all.

These two teams say that the microbe, known as GFAJ-1, is somewhat weird, due to the fact that it can survive amid ultra-high concentrations of arsenic. But they confirm the widely held view among microbiologists that GFAJ-1 did not rewrite the existing rules of life — an extraordinary claim that was implied by the initial study, which made a huge splash in December 2010.

"The new research clearly shows that the bacterium, GFAJ-1, cannot substitute arsenic for phosphorus," the journal Science, which published the initial findings as well as today's follow-up studies, said in an editorial statement.

Case closed?
One of the authors of the new research, University of British Columbia microbiologist Rosie Redfield, was among the most outspoken critics of the original study — and she said that as far as she was concerned, today's publication closes the case. "This isn't an area I have any special interest in, or any funding for," she told me in an email.

Over the past 19 months, Redfield has focused on the analysis of GFAJ-1's DNA more as a case study in open science — a perspective that focuses on freely sharing the results of the research process as they come to light. The study that she and her colleagues authored has been available for months on the ArXiv pre-print website. (The other study, conducted by researchers at ETH Zurich in Switzerland, became public just today.)

Science's editors decided to time today's online publication of the two studies to coincide with a talk that Redfield was due to give at a conference in Ottawa on evolutionary biology. Redfield said last week on her blog that she'd be discussing the results of her group's research, including the Science paper, during her talk. When I contacted her on Friday about the impending publication, she expressed surprise that the journal accelerated its publishing schedule.

"What? No!" she wrote in an initial email. "Must be because of my Evolpalooza talk that night."

The print version of the papers released tonight are to appear in Science later this month.

In the past, the lead researcher for the original study of GFAJ-1, Felisa Wolfe-Simon, has declined to comment in detail about the follow-up experiments that have raised questions about her group's work. She has said such comments would have to wait until those experiments were described in peer-reviewed research articles. But due to the publication in Science, Wolfe-Simon responded to my emailed inquiries at greater length.

She acknowledged that the follow-up experiments failed to find evidence that compounds containing arsenic, known as arsenates, were being taken up into the molecular machinery of GFAJ-1's life processes, such as DNA. However, she said those experiments were apparently conducted under conditions that differed from those surrounding the original experiment.

"We do not know the history of the cells in these new papers," she wrote. "In general, it requires more evidence to publish something unexpected — e.g., that cells can thrive in arsenic and that arsenate is found inside the cells, than something that everyone expects — e.g. that arsenate is not found inside cells or DNA.

"Our original work and data was in fact given high scrutiny, as standards are almost always higher for evidence for things that are unexpected. We are actively following the arsenic in our cells and will know more in the next few months." (The full email exchange is laid out in a comment below.)

Sensationalism and skepticism
The original point of the arsenic-life experiment was to see whether organisms on Earth could be coaxed to use arsenic, which generally acts as a poison, in place of phosphorus, which is generally seen as one of the essential chemical building blocks of life. The structure of those two elements on the atomic level is similar, which is a big reason why substituting one for the other is so lethal.

If some types of organisms, even bacteria, could live on arsenic, that would upset the mainstream view of how life works. Such a finding, if confirmed, would potentially lead to a wider search for "weird life" — not only on Earth, but also in extraterrestrial environments such as the Martian subsurface or the hydrocarbon lakes of Titan.

Wolfe-Simon and her colleagues conducted their search for arsenic-eating life by taking samples from the arsenic-rich sediments of California's Mono Lake, then turning up the dial on the arsenic and turning down the dial on the phosphorus in their laboratory's cell cultures. They isolated a strain of bacteria that grew in a setting with ultra-high concentrations of arsenic and seemingly negligible amounts of phosphorus. (The strain's name, GFAJ-1, stands for "Give Felisa a Job.")

Analysis of the cells led them to conclude that arsenic was being used in place of phosphorus, even in GFAJ-1's DNA molecules. The findings created a sensation when they were announced. "We're talking about an organism that we think ... is replacing phosphorus with arsenic," Mary Voytek, the head of NASA's astrobiology program, said at the time. "This is a huge deal."

The case sparked a huge backlash as well. Many scientists questioned the results — not only in comments to journalists, but also in blog postings and Twitter updates. Redfield suspected that the detection of arsenic was due to sample contamination rather than an uptake into DNA molecules. The experiment in which she was involved, conducted with Princeton's Marshall Louis Reaves as lead researcher, reported finding "only trace amounts of free arsenate" and no chemically bound arsenic compounds in the DNA samples they extracted from GFAJ-1.

In their Science paper, the researchers say the reason for the dramatically different results "is not clear," but they also note that "differences in DNA purity can readily explain" the discrepancies.

How GFAJ-1 works
The other study published today, with ETH Zurich's Tobias Erb as lead author, takes a wide-angle view of GFAJ-1, using mass spectrometry and other tools to trace the bacteria's chemical processes on the molecular level. They found that the microbes could grow with even less phosphorus than the tiny amount that was provided in the experiments by Wolfe-Simon and her colleagues. But when the phosphorus concentration was reduced to nearly nothing (less than 0.3 micromolar), no growth was observed.

Some arsenic compounds formed in the culture, but at a level that was more likely associated with non-biological chemical processes, Erb and his colleagues said. They noted that such compounds are also found in garden-variety E. coli bacteria when they're grown in cultures containing arsenic. This suggests that the detection of arsenic-containing compounds "might not be of physiological relevance," they wrote.

The two groups of researchers acknowledged that there was something extraordinary about GFAJ-1, in that it could grow amid ridiculously high concentrations of arsenic — roughly an order of magnitude higher than previously seen for other organisms, the Swiss-based scientists said. "The molecular basis for arsenate resistance in GFAJ-1 might be the subject of further investigations," they wrote.

It's also noteworthy that GFAJ-1 could survive amid ridiculously low concentrations of phosphorus. Wolfe-Simon and her colleagues said that was because the bacteria switched to metabolizing arsenic. But Reaves, Redfield and their colleagues said it was more likely that GFAJ-1 used a metabolic mechanism to enrich the tiny amount of phosphorus it could grab onto.

More research ahead
In her emails, Wolfe-Simon said the data reported in the newly published research did not contradict the thrust of her own studies, which are continuing. She said it's possible that the arsenic compounds taken up by GFAJ-1 become less stable "once cells are broken open."

"We expect to have our own results ready for publication in the next few months," she wrote. "We are focused on the questions, 'Where exactly is the arsenate going?' and 'How does this microbe survive in high arsenate?' These results will speak to the flexibility of the periodic table for life, so [they] merit the most thorough and careful analysis we can achieve."

In their statement, Science's editors took a different perspective.

"The new research shows that GFAJ-1 does not break the long-held rules of life, contrary to how Wolfe-Simon had interpreted her group's data," they said. "The scientific process is a naturally self-correcting one, as scientists attempt to replicate published results. Science is pleased to publish additional information on GFAJ-1, an extraordinarily resistant organism that should be of interest for further study, particularly related to arsenic-tolerant mechanisms."

Redfield agreed that GFAJ-1 was worthy of further study, even if she's not going to be doing it. "I think all organisms turn out to have interesting tweaks," she told me in her email. "We certainly know very little about the biology of GFAJ-1, and there are complications I never sorted out."

So just how big of a deal did the "arsenic life" controversy turn out to be? To my mind, the case seems likely to take its place among the other great disputed claims in science, ranging from cold fusion to Martian nanofossils and the missing-link primate. It also feeds into the debate over the best ways to distribute and verify scientific findings. Lots of folks will be weighing in on these questions over the next day or two, and you can have the last word in the comment section below.

Previous chapters in the weird-life saga:

• DNA study counters arsenic-life claims
• One year later, 'arsenic life' debate still percolates
• Strange find on Titan sparks chatter about life
• Mars methane mystery: What's making the gas?
• What exactly is life, anyway?
• Cosmic Log archive on arsenic life

In addition to Reaves and Redfield, the authors of "Absence of Detectable Arsenate in DNA from Arsenate-Grown GFAJ-1 Cells" include Sunita Sinha, Joshua D. Rabinowitz and Leonid Kruglyak.

In addition to Erb, the authors of "GFAJ-1 Is an Arsenate-Resistant, Phosphate-Dependent Organism" include Patrick Kiefer, Bodon Hattendorf, Detlef Günther and Julia A. Vorholt.

Science said the two papers, along with an editorial statement, were being released at 8 p.m. ET July 8 "to coincide with a related conference." That was a reference to Redfield's talk at the Evolution Ottawa conference.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Henry Bortman / 2010

Other scientists are analyzing the controversial strain of bacteria that biologist Felisa Wolfe-Simon and her colleagues found in California's Mono Lake.

It's been one year since researchers shook up the scientific world by claiming they bred bacteria that used arsenic in place of phosphorus, and the controversy is still simmering: The lead researcher and her critics say they're taking a closer look at the microbe at the center of the "weird life" claims.

After hitting the highs and the lows of academic acclaim, Felisa Wolfe-Simon has left her original research group and joined up with Lawrence Berkeley National Laboratory in California to continue her research into the bacterium known as GFAJ-1, which gets its name from the acronym for "Give Felisa a Job." (No joke!)

"There is so much work to do we're focusing on that and look forward to communicating our efforts in the coming months," Wolfe-Simon told me in an email this week.

Meanwhile, Wolfe-Simon's highest-profile critic, University of British Columbia microbiologist Rosie Redfield, took on the task of replicating the GFAJ-1 experiment. "I'm doing this even though I agree with all the other researchers who said this result is almost certainly wrong," Redfield told me. "Scientifically, it's really kind of a waste of time to try to replicate this yourself. But there's always the possibility that you could be wrong. And more than that, there was just a general sense that, you know, somebody should try."

Redfield has sent purified DNA samples to collaborators at Princeton University for mass spectrometry analysis — to see whether any arsenic was really taken up into the molecular structure. "We just got the DNA from Rosie Redfield," one of those collaborators, Leonid Kruglyak, told me this week. A graduate student in Kruglyak's lab, Marshall Louis Reaves, is currently working out the protocols for analyzing the DNA.

"We want to be able to fragment the DNA and run the fragments on the mass spectrometer," Krugylak said. "Those fragments should look quite different in the mass spectrometer if there is arsenate."

Just today, another team of researchers, led by Simon Silver of the University of Illinois at Chicago, announced that they have sequenced GFAJ-1's genome and will be analyzing it for new clues in the case.

Argonne National Laboratory's Jack Gilbert, a member of the team, characterized himself as a "100 percent skeptic" about the findings announced a year ago, but said that the gene sequence was still worth having. He and his colleagues have already found some interesting genetic twists, even if there's no evidence of arsenic in the DNA. "It's interesting to have this information to determine what the mechanism might be if other evidence shows this to be true," he explained.

Gilbert said it was mere coincidence that the genome sequence was published online exactly one year after Wolfe-Simon and her colleagues kicked off the controversy. "I hadn't even considered that today was the anniversary," he told me.

Why all the fuss?
The case of GFAJ-1 is significant on more than one level.

If the central claim of the original paper holds true, that means the machinery of life can be tinkered with to replace one seemingly essential chemical — phosphorus — with a different chemical that's seemingly inimical to life. One of Wolfe-Simon's original collaborators, Arizona State University astrobiologist Paul Davies, has long maintained that "weird life," built on a different biochemical platform, could exist right under our noses and we wouldn't know it.

The prospect of weird life on Earth would also argue in favor of widening the search for weird life on other worlds, perhaps as close as Mars or the Saturnian moon Titan. That's what led NASA to tout the research a year ago as having extraterrestrial implications. "The definition of life has just expanded," said Ed Weiler, an associate administrator at the space agency. The news reports went even farther. Here's a typical headline: "NASA Discovers Alien Life in California."

Actually, what Wolfe-Simon and her colleagues did was to take an existing strain of salt-loving bacterla from California's Mono Lake, and try to breed it in the presence of high concentrations of arsenic. GFAJ-1 emerged as the best prospect: The research team said it seemed to take hold in the high-arsenic environment, and they said their molecular analysis suggested that arsenic-based compounds known as arsenates were incorporated in the place of phosphates.

The bacteria in the arsenic-rich culture weren't aliens at all. But for many chemists and microbiologists, the research team's claims, published online by the journal Science on Dec. 2, 2010, were as hard to believe as reports of a UFO landing.

One chemist, Steven Benner of the Florida-based Foundation for Applied Molecular Evolution, said he bet Wolfe-Simon $100 that the arsenic wasn't taken up in the DNA. Benner said in an email this week that the proposition was "still in limbo ... so the bet is not yet collected." (Wolfe-Simon told me she doesn't remember the bet.)

The skepticism over the reported results erupted almost immediately in a wave of blog postings and Twitter updates from commentators and scientists, including Redfield. As a result, the #arseniclife case quickly became a case study for instant peer review, mediated by the Internet. It also turned into a case study for open science, in which researchers share their results as they become available rather than holding them back until they're published in a journal.

Redfield emerged as a strong voice, for the skeptics as well as for the open-science movement. Her technical criticisms focused on the way that the bacteria samples were handled. "The way they isolated their DNA was almost 'I can't believe they did this' badly done," she told me this week. Such criticism led Science's editors to hold back the on-paper publication of the research for months, until eight sets of technical comments could be collected from Redfield and other observers and vetted through peer review. Wolfe-Simon and her colleagues were also given space to respond to the technical comments.

"That was pretty unprecedented," said Ginger Pinholster, director of the Office of Public Programs at the American Association for the Advancement of Science, which publishes the journal Science.

The next steps
Since then, the focus has shifted from the headlines to the labs. A Popular Science profile of Wolfe-Simon created a bit of a stir a couple of months ago: She was quoted as saying that she was "basically evicted" from her research group and worried that "it's quite possible that my career is over."

But during this week's email exchange, Wolfe-Simon told me that the "Popular Science article quotes were not what I said," and that "what matters now is what these organisms are telling us about biology, and that is my focus." Here are some reflections on the one-year anniversary from one of her emails to me:

"What a busy year it has been!

"With the generous support of NASA, we are able now to dive deep and explore this scientific discovery. After such a discovery comes the time-intensive process of rigorous testing. We aim to unravel the mechanisms behind how this microbe accomplishes the ability to flourish and grow despite uptake and utilization of arsenic. This systematic rigorous testing is critical and needed to build upon an initial discovery of this type.

"To this end, I have joined the Lawrence Berkeley National Laboratory in collaboration with Dr. John Tainer and his group there. LBNL provides the diverse intellectual and material resources of a major national laboratory, affording us the opportunity to pursue our efforts to test multiple aspects and implications of the work efficiently and stringently. LBNL synergistically complements the generous financial support from NASA.

"Currently, we have made significant headway in optimizing the growth conditions of GFAJ-1 and preparing samples for a wide range of analyses, including biomolecule crystallization and metabolite characterization. There is so much work to do we're focusing on that and look forward to communicating our efforts in the coming months. ...

"I maintain my serious commitment to science and the process of data-driven research. I look forward to speaking with you some time in the not too distant future after we make additional scientific progress."

Other researchers are delving into the mysteries of GFAJ-1 as well, even though they don't think the claims about arseno-DNA and other "weird life" wonders will hold up. "I don't have any money for this," Redfield told me. "This is just a side project in what would be my spare time, if professors have any spare time."

Redfield says the projects she gets paid for are more likely to be scientifically productive, but they're not as interesting to the general public. "This struck me as an opportunity to do science openly in a circumstance where people would be actually interested in what I'm doing, and what the results were," she said.

Now the fruits of her GFAJ-1 labors are in the hands of Kruglyak and his colleagues. If the arsenic in the samples has really been incorporated in the DNA, rather than merely representing sample contamination, traditional genetic sequencing techniques would not work. "They could give all sorts of unpredictable results," Kruglyak said. That's why mass spectrometry has to come into play.

Kruglyak can't predict how long it will take to get the answers. "It always takes longer than whatever I would say," he told me. "I would hope it's weeks, not months."

Meanwhile, Gilbert and his colleagues will continue studying GFAJ-1's genetic makeup. He told me "there's nothing spectacularly amazing" about the bacteria, which was not subjected to the high-arsenic treatment applied by Wolfe-Simon's team and by Redfield. But Gilbert said the raw bacteria's genome has some intriguing twists nevertheless.

"What is quite interesting is that this has very few arsenic resistance genes, i.e., it does not have the typical suite of genes that would make the cell resistant to arsenic in the environment," he told me in an email. Further study of the genome may at last point to an explanation for GFAJ-1's affinity for arsenic — but as of today, one year after the bacteria came onto the world scene, Gilbert can't predict what that explanation might be.

"We will prod and poke at this thing for another year, and see if there's anything more interesting," he said.

Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.