You’ve got to hand it to NASA for their ability to routinely make a ruckus: Whereas many scientists struggle to elicit anything more than yawns from their audiences as they try to explain why their work matters (and, more pointedly, why it deserves tax or grant money), the whole “aliens” and “outer space” thing gives NASA a more receptive audience, and they know how to press that audience’s buttons.
In this case, though, things have gotten a little out of hand: A NASA press release on “an astrobiology finding that will impact the search for evidence of extraterrestrial life” morphed into Jason Kottke’s “Has NASA discovered extraterrestrial life?“, a question which he admitted was hyperbolic, which in turn mutated into progressively crazier herp-a-derp Internet speculation. Wired’s Alexis Madrigal tweeted, “I’m sad to quell some of the @kottke-induced excitement about possible extraterrestrial life. I’ve seen the Science paper. It’s not that.”
What is it, then? NASA’s press conference isn’t until 2pm EST tomorrow, so we won’t know for sure, but it seems to relate to the decidedly less sexy, though still intriguing, research done on organisms that use arsenic rather than phosphorus for energy.
One of the four participants in NASA’s press conference tomorrow is NASA astrobiology research fellow Felisa Wolfe-Simon, who has spent two years researching Yosemite Park’s Mono Lake, which has one of the highest natural concentrations of arsenic of any site in the world. Skymania spoke to astrobiologist Lewis Dartnell, who said, “I’m 90 per cent certain that Felisa has found something in Mona Lake and they have been able to demonstrate in some way that it uses arsenic in its metabolism rather than be poisoned by it.”
You may recall from your high school biology class that ATP, or adenosine triphosphate, is the so-called “energy currency” of the cell, and powers many key metabolic functions; key to ATP’s structure is the element phosphorus. Arsenic sits directly below phosphorus on the periodic table of elements and can do many of the same things chemically, but it’s usually poisonous to living things. Arsenic-powered organisms, then, would indeed represent different forms of life from those which we’re most familiar, both because they’d have ATP-like molecules with arsenic swapped in in phosphorus’ place and because they had evolved mechanisms such that arsenic didn’t kill them.
Update: This does make things a little more interesting; the organisms may also incorporate arsenic in their DNA in the place of phosphorus.
Using radioactive isotopes of arsenic, the researchers followed the path arsenic took in the bacteria. They saw that it completely replaced phosphorus in the bacterial cells, right down to the organism’s DNA.
“This organism has dual capability,” said researcher Paul Davies, a cosmologist, astrobiologist and theoretical physicist at Arizona State University. “It can grow with either phosphorous or arsenic. That makes it very peculiar, though it falls short of being some form of truly ‘alien’ life belonging to a different tree of life with a separate origin. However, GFAJ-1 may be a pointer to even weirder organisms. The holy grail would be a microbe that contained no phosphorus at all.”
Update2, 12/2: Yup. The embargo lifted, NASA dishes out the dirt:
“We know that some microbes can breathe arsenic, but what we’ve found is a microbe doing something new — building parts of itself out of arsenic,” said Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow in residence at the U.S. Geological Survey in Menlo Park, Calif., and the research team’s lead scientist. “If something here on Earth can do something so unexpected, what else can life do that we haven’t seen yet?”
The newly discovered microbe, strain GFAJ-1, is a member of a common group of bacteria, the Gammaproteobacteria. In the laboratory, the researchers successfully grew microbes from the lake on a diet that was very lean on phosphorus, but included generous helpings of arsenic. When researchers removed the phosphorus and replaced it with arsenic the microbes continued to grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new GFAJ-1 cells.
The key issue the researchers investigated was when the microbe was grown on arsenic did the arsenic actually became incorporated into the organisms’ vital biochemical machinery, such as DNA, proteins and the cell membranes.
NASA Watch’s Keith Cowing writes that “[r]eliable sources within the Astrobiology community tell me that the announcement does indeed concern Arsenic-based biochemistry and the implications for the origin of life on Earth, how it may have happened more than once on our planet, and the implications for life arising elsewhere in the universe.”
Here’s an abstract for one recent study on the subject, for which Wolfe-Simon is the principal author:
All known life requires phosphorus (P) in the form of inorganic phosphate (PO43‑ or Pi) and phosphate-containing organic molecules. Pi serves as the backbone of the nucleic acids that constitute genetic material and as the major repository of chemical energy for metabolism in polyphosphate bonds. Arsenic (As) lies directly below P on the periodic table and so the two elements share many chemical properties, although their chemistries are sufficiently dissimilar that As cannot directly replace P in modern biochemistry. Arsenic is toxic because As and P are similar enough that organisms attempt this substitution. We hypothesize that ancient biochemical systems, analogous to but distinct from those known today, could have utilized arsenate in the equivalent biological role as phosphate. Organisms utilizing such ‘weird life’ biochemical pathways may have supported a ‘shadow biosphere’ at the time of the origin and early evolution of life on Earth or on other planets. Such organisms may even persist on Earth today, undetected, in unusual niches.
All of which is potentially useful for biologists earthly and otherwise, the sort of trivia geeks lap up, and — let’s be honest here — probably not too interesting to most laypeople. Again, props to NASA for knowing how to gin up interest, but it’s a shame so much sanctioned crazy talk from mainstream outlets surfaces in the process.
Update3: Following NASA’s announcement, friend of Geekosystem and super awesome science blogger Hannah Waters, whose blog, Culturing Science, you should read, summarizes as follows:
1) this is not a new life form. this microbe is able to incorporate arsenic into it’s DNA -but it evolved from an organism with phosphate-backbone DNA. WE ARE RELATED TO THIS GUY
2) it’s not clear whether it even uses arsenic in its DNA/proteins in its natural habitat. More like we trained it to use arsenic. It was grown in liquid including arsenic in the lab, which would normally kill any other cell. But this guy was able to survive, and then when the scientists gradually diluted out the phosphate (normal DNA backbone), it incorporated arsenic. So – we know that it CAN use arsenic, whether it does naturally is unclear
3) BUT THIS IS STILL AWESOME! arsenic was very common on our early planet and it’s been unclear how it was dealt with. there are organisms out there that can survive it! cool! and it provides a whole new molecular biology to study and learn about – one that involves a an element that is deadly to most life on this planet
(via Skymania, NASA Watch)
Published: Dec 1, 2010 11:28 am