Something weird is living in Mono Lake. It's not like us. It is so unlike us, in fact, that when you feed it arsenic, an element that is toxic to almost all of life as we know it, it doesn't die: It eats it and keeps on growing.
Felisa Wolfe-Simon dug the bacterium, a member of the Halomonadaceae family called GFAJ-1, from the muddy bottom of briny, arsenic-rich Mono Lake in California. Back in the lab, she and her team put it on a radical diet, cutting off its supply of essential phosphorous and steadily replacing it with arsenic. The poor little thing should have died. But, as Wolfe-Simon told reporters at a NASA press conference today, "Not only did this microbe cope, but it grew and it thrived. That was amazing. Nothing should have grown. Put your plant in the dark, it doesn't grow." (Click here for the NASA press release.)
To find out exactly what the microbe was doing with all that arsenic, Wolfe-Simon and her team tagged the arsenic with radioactivity and tracked it as it was incorporated into the body of the bacterium. Gradually, arsenic took the place of phosphorous in the bacterium's molecules. According to the team's Science paper, the arsenic went right down to the bacterium's DNA (though some scientists aren't convinced of this).
How amazing is that? As Caleb Scharf, an astrobiologist at Columbia University, told Dennis Overbye at the New York Times, "It's like if you or I morphed into fully functioning cyborgs after being thrown into a room of electronic scrap with nothing to eat."
The research was partly funded by NASA's Astrobiology program. Why should astrobiologists, who spend their days and nights thinking about life on other planets and moons, care about some little beasties living in the muck of a toxic lake near Yosemite? First, this is more evidence that life can thrive in an environment that should by all rights be barren. But the bigger news is that life can operate successfully on a novel biochemical platform, one that relies on a different set of molecules from those that make up life as we know it.
The essential components of "normal" cells are carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorous. But, as Wolfe-Simon and her colleagues note, phosphorous is the misfit of the bunch, because it probably wasn't widely available to early Earth life. This discrepancy led the scientists to hypothesize that ancient organisms might have used arsenic, which occupies the slot right below phosphorous on the period table, in place of phosphorous. In fact, arsenic and phosphorous are chemical doppelgangers; it's this chemical similarity that makes arsenic so dangerous to familiar biology.
The discovery that a microbe can
replace phosphorous with arsenic has "cracked open the door to what's
possible for life elsewhere in the universe," said Wolfe-Simon. What
does this mean for scientists searching for evidence of life on other
worlds? Though they won't start "following the arsenic" any time soon,
they will have to accept the humbling challenge of hunting for life as
we don't know it.
(Curious about that other form of alien life? You know, the one that populates the blogosphere and the Twitterverse and metabolizes press releases into elaborate, romantic speculation? Check out the Columbia Journalism Review's take on the pre-press-conference frenzy on this story. Also recommended: Ed Yong's report at Not Exactly Rocket Science.)
December 3, 2010 12:36 AM
Just a hoax I think. Or else, there gonna be more cyborgs in the next decades.