Epic Fail for Induction: NASA Discovers Bacteria That Lives on Arsenic (Question Mark)

A friend and I have had a running dispute on whether intelligent life is “out there” in the Universe.  Neither of us knows, obviously, so we’re both forced to abstract crudely from what we laypersons know about biology or astrophysics.  I have long been a subscriber to the Rare Earth hypothesis, popularized by geologist and paleontologist Peter Ward and astronomer Donald Brownlee, in their book Rare Earth: Why Complex Life Is Uncommon in the Universe.  The thrust of the argument: Life may be out there, all over the place, in the form of microbes–but intelligent life appears to require billions of years of stellar stability, terrestrial (solid-ground surface) planets, proper atmospheric and chemical balances and temperate conditions on the surface.  Put differently, we’re asking for confluences of the statistically-improbable to exist for billions of years for intelligent life to have a chance to evolve.

Even in the case of simple, unicellular organisms such as bacteria whose uncounted specimens have proliferated everywhere, there is still a very basic constraint in the organic elements–carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus–which are the essential components of the basic organic compounds.

Today this friend and interlocutor, ever-hopeful for a Universe teeming with extraterrestrials, sent me a short, excited entry in Wired that claims a wrinkle has now been added to this assumed order–a wrinkle the size of a poisonous lake.  Mono Lake in California is a 13-mile-wide volcanic basin with extremely high salinity.  NASA astrobiologist Richard Hoover was attracted to Mono Lake precisely because this toxic environment was known to host a large number of small life forms, including brine shrimp, a type of fly that can dip underwater in air bubbles, cyanobacteria and filamentious algae.  Hoover’s purpose in studying the lake was to search for a specimen a bit more-radical than these, one that couldn’t just survive in this seemingly-hostile environment but was adapted to grow exclusively within it.

He found this specimen after a day’s field trip out to Mono Lake.  Mud samples taken from the lake yielded a new microorganism–Spirochaeta americana. “Big deal,” some will say, “He discovered a new species.”  Well, it’s anaerobic.  “Yeah, there are lots of anaerobic bacteria out there,” those who recall their last biology class will reply.  The interesting development is that this bacteria appears to synthesize its DNA from arsenic.  That’s right, the poison; it apparently uses arsenic in the place of phosphorus as a component of its DNA.

“Huh…”

This, if true, would be a pretty big deal.  It opens the door to radical claims that the previously-mentioned organic elements–carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus–are in fact not essential for prototypical life to emerge.  If you are a subscriber to the magazine Science, as of today you can read the paper in which NASA’s lab scientists press this claim.

Not so fast. The Week‘s Opinion Brief led the way today in assembling astonished, skeptical or unimpressed respondentsThe Week‘s assemblages are enlightening because they juxtapose persuasive claims that the latest news changes everything with insightful claims that what we have here is either misunderstanding or the amusing exception that really bears out the rule.  I’ll juxtapose the most- and least-excited claims assembled in the Opinion Brief here:

A science fiction writer speaking to FOXNews.com claimed that “If there is more than one recipe that makes life, then there are chances of rolling the dice in a chemical soup of all over the universe, and the chances of that chemical soup giving rise to life is much larger.”

Alternatively, Phil Plait, blogging for Discover magazine, expressed exasperation as early as Tuesday, November 30th that NASA’s announcement of a press conference 2 days hence was overly-theatrical; the press release had stated that the upcoming press conference would “discuss an astrobiology finding that will impact the search for evidence of extraterrestrial life.”  Plait pointed out after the reveal that this claim led to deflation and disappointment, because people were sorta led to expect…well, some positive indication of extraterrestrial life, somewhere.  Instead we have circumstantial evidence of a biochemical substitution that would imply that life could spread to certain environments we thought it couldn’t.

Circumstantial?”  That’s right, Hoover and NASA aren’t certain yet that this organism is “digesting” (rather than storing) the arsenic.  Carl Zimmer, another blogger for Discover magazine, writes in “Of Arsenic and Aliens” that NASA’s research hasn’t yet confirmed that Spirochaeta americana really synthesizes DNA from arsenic:

“Wolfe-Simon and her colleagues reared the bacteria in their lab, initially feeding them a typical diet of essential nutrients, including phosphate. But then they gradually reduced the phosphate in their diet and replaced it with arsenate. Before long, as they report today in Science, the bacteria were growing nicely on an all-arsenate diet, without a speck of phosophate. The scientists then probed the DNA of the bacteria and concluded that they were sticking the arsenate into the DNA in place of phosphate. Phosphate is also vital for other molecules, such as proteins, and the scientists found phosphate in them as well. In other words–arsenic-based life.

“Or…maybe not. In Science, reporter Elizabeth Pennisi writes that some scientists are skeptical, seeing other explanations for the results. One possibile alternative is that the bacteria are actually stuffing away the arsenic in shielded bubbles in huge amounts.”

Those who have read this blog for a while may recall that the Liberal Ironist has witnessed the rising and falling emotions of 2 recent cases of overeager science news–experiencing the premature excitement himself in a report in The Economist claiming the laws of nature appear to break down in deep space and alternately feeling nonplussed from the start by claims of yet-another Earth-sized planet that probably doesn’t otherwise resemble Earth at all.  “This is the sort of thing that happens when current science research gets out to a broader public,” a friend who is a graduate student in physics lamented in response to the reporting on the former story.  “The journalist writing the story takes 1 academic paper that conjectures a theory…and writes about it as if it were true.”

So, until follow-up research confirms that Spirochaeta americana can live permanently with sole exposure to arsenic and without access to phosphorus, you say “new form of life,” I say “potahto.”

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3 thoughts on “Epic Fail for Induction: NASA Discovers Bacteria That Lives on Arsenic (Question Mark)

  1. J-Doug

    It doesn’t use arsenic in place of phosphorus as a nutrient–that’s not news at all. The finding is it replaced phosphorus with arsenic as part of it’s DNA building block. You can argue the finding is wrong, but you’re misrepresenting the finding.

    Reply
    1. liberalironist Post author

      I know, I misspoke. I’ve fixed it. I was thrown off because phosphorus links the base pairs in DNA together but doesn’t actually occur in them. I should have figured that was where the arsenic bonding allegedly occurs in Spirochaeta americana, but I’m an ironist, not a biologist.

      Reply
  2. Pingback: A Poison Pill in NASA’s Arsenic-Laced Bacteria? | The Liberal Ironist

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