GFAJ-1 is an arsenate-resistant, phosphate-dependent organism — title of the paper by Erb et al, Science, July 2012
Everyone will recall the hype and theatrical gyrations which accompanied NASA’s announcement in December 2010 that scientists funded by NASA astrobiology grants had “discovered alien life” – later modified to “alternative terrestrial biochemistry” which somehow seemed tailor-made to prove the hypothesis of honorary co-author Paul Davies about life originating from a “shadow biosphere”.
As I discussed in The Agency that Cried “Awesome!, the major problem was not the claim per se but the manner in which it was presented by Science and NASA and the behavior of its originators. It was an astonishing case of serial failure at every single level of the process: the primary researcher, the senior supervisor, the reviewers, the journal, the agency. The putative and since disproved FTL neutrinos stand as an interesting contrast: in that case, the OPERA team announced it to the community as a puzzle, and asked everyone who was willing and able to pick their results apart and find whatever error might be lurking in their methods of observation or analysis.
Those of us who are familiar with bacteria and molecular/cellular biology techniques knew instantly upon reading the original “arsenic life” paper that it was so shoddy that it should never have been published, let alone in a top-ranking journal like Science: controls were lacking or sloppy, experiments crucial for buttressing the paper’s conclusions were missing, while other results contradicted the conclusions stated by the authors. It was plain that what the group had discovered and cultivated were extremophilic bacteria that were able to tolerate high arsenic concentrations but still needed phosphorus to grow and divide.
The paper’s authors declined to respond to any but “peer-reviewed” rebuttals. A first round of eight such rebuttals, covering the multiple deficiencies of the work, accompanied its appearance in the print version of Science (a very unusual step for a journal). Still not good enough for the original group: now only replication of the entire work would do. Of course, nobody wants to spend time and precious funds replicating what they consider worthless. Nevertheless, two groups finally got exasperated enough to do exactly that, except they also performed the crucial experiments missing in the original paper: for example, spectrometry to discover if arsenic is covalently bound to any of the bacterium’s biomolecules and rigorous quantification of the amount of phosphorus present in the feeding media. The salient results from both studies, briefly:
– The bacteria do not grow if phosphorus is rigorously excluded;
– There is no covalently bound arsenic in their DNA;
– There is a tiny amount of arsenic in their sugars, but this happens abiotically.
The totality of the results suggests that GFAJ-1 bacteria have found a way to sequester toxic arsenic (already indicated by their appearance) and to preferentially ingest and utilize the scant available phosphorus. I suspect that future work on them will show that they have specialized repair enzymes and ion pumps. This makes the strain as interesting as other exotic extremophiles – no less, but certainly no more.
What has been the response of the people directly involved? Here’s a sample:
Ronald Oremland, Felisa Wolfe-Simon’s supervisor for the GFAJ-1 work: “… at this point I would say it [the door of “arsenic based” life] is still just a tad ajar, with points worthy of further study before either slamming it shut or opening it further and allowing more knowledge to pass through.”
John Tainer, Felisa Wolfe-Simon’s current supervisor: “There are many reasons not to find things — I don’t find my keys some mornings. That doesn’t mean they don’t exist.”
Michael New, astrobiologist, NASA headquarters: “Though these new papers challenge some of the conclusions of the original paper, neither paper invalidates the 2010 observations of a remarkable micro-organism.”
At least Science made a cautious stab at reality in its editorial, although it should have spared everyone — the original researchers included — by retracting the paper and marking it as retracted for future reference. The responses are so contrary to fact and correct scientific practice (though familiar to politician-watchers) that I am forced to conclude that perhaps the OPERA neutrino results were true after all, and I live in a universe in which it is possible to change the past via time travel.
Science is an asymptotic approach to truth; but to reach that truth, we must let go of hypotheses in which we may have become emotionally vested. That is probably the hardest internal obstacle to doing good science. The attachment to a hypothesis, coupled with the relentless pressure to be first, original, paradigm-shifting can lead to all kinds of dangerous practices – from cutting corners and omitting results that “don’t fit” to outright fraud. This is particularly dangerous when it happens to senior scientists with clout and reputations, who can flatten rivals and who often have direct access to pop media. The result is shoddy science and a disproportionate decrease of scientists’ credibility with the lay public.
The two latest papers have done far more than “challenge” the original findings. Sagan may have said that “Absence of evidence is not evidence of absence,” but he also explained how persistent lack of evidence after attempts from all angles must eventually lead to the acceptance that there is no dragon in that garage, no unicorn in that secret glade, no extant alternative terrestrial biochemistry, only infinite variations at its various scales. It’s time to put “arsenic-based life” in the same attic box that holds ether, Aristotle’s homunculi, cold fusion, FTL neutrinos, tumors dissolved by prayer. The case is obviously still open for alternative biochemistry beyond our planet and for alternative early forms on earth that went extinct without leaving traces.
We scientists have a ton of real work to do without wasting our pitifully small and constantly dwindling resources and without muddying the waters with refuse. Being human, we cannot help but occasionally fall in love with our hypotheses. But we have to take that bitter reality medicine and keep on exploring; the universe doesn’t care what we like but still has wonders waiting to be discovered. I hope that Felisa Wolfe-Simon remains one of the astrogators, as long as she realizes that following a star is not the same as following a will-o’-the-wisp — and that knowingly and willfully following the latter endangers the starship and its crew.
Images: 2nd, Denial by Bill Watterson; 3rd, The Fool (Rider-Waite tarot deck, by Pamela Cole Smith)