2 December 2010
NASA Scientists Find Microbes with Arsenic DNA
Posted by Ryan Anderson
As you have probably heard, NASA had a big news conference slated for this afternoon. When the announcement went out, it prompted all sorts of speculation, but in the last day or so the cat has basically been out of the bag: NASA astrobiologists have found bacteria living in Mono Lake, CA that use arsenic rather than phosphorus as the backbone of it’s DNA and other biomolecules like ATP.
This is a pretty big deal! Until now, everyone thought that life required the elements C,H,N,O,P,S to survive, but the Mono Lake bacteria laugh in the face of that idea and use something typically thought of as a deadly poison as a fundamental building block. Felisa Wolfe-Simon, the lead author of the study summed things up nicely when she said that “It has solved the challenge of being alive in a very different way.”
It’s not all happy thoughts though: chemist Steve Benner expressed some skepticism about the arsenic-based DNA claim, pointing out that arsenate would form a much weaker link in the DNA polymer that would break down in a matter of minutes in normal earth environments. He wasn’t all doom and gloom though, because he pointed out that extremely cold environments elsewhere in the solar system might be more favorable for arsenic-based DNA.
Pan Conrad, an astrobiologist on the MSL mission was also at the press conference. She welcomed the idea of arsenic as a potential alternative component for life because it broadens the range of possible habitats for life in the universe. It may not be the ideal atom, but it works! In terms of MSL experiments, she pointed out that there are instruments that can measure the elements in a sample (APXS and ChemCam) and an organic chemistry lab (SAM) so by looking for organics plus unusual metals you could start to interpret what you’re seeing.
I thought it was great to hear Wolfe-Simon say during the question session that there wasn’t a “eureka moment” where they knew what they had found, it was more like “Hey, this isn’t right.” It reminds me of this Isaac Asimov quote:
The most exciting phrase to hear in science, the one that heralds new discoveries, is not ‘Eureka!’ (I’ve found it!), but ‘That’s funny…’ -Isaac Asimov.
Unfortunately, I’m super busy so I can’t write more right now, but I’ll leave you with this YouTube video summarizing the results:
Update: Also, check out this excellent summary of the actual Science paper over at Pharyngula. Bottom line is that this is cool research but not as ground-breaking as it sounds at first.
Update 2: For some reason the timestamp on this post is messed up. It was first posted around 2:40 pm Eastern time, Dec. 2, 2010.
Is it fair to say “NASA astrobiologists have found bacteria living in Mono Lake, CA that use arsenic rather than phosphorus…”? Isn’t it more accurate to say “NASA astrobiologists have trained bacteria originally living in Mono Lake, CA to use arsenic rather than phosphorus…”
From my reading of this issue, it sounds like they basically got some of these bugs to survive using arsenic in place of phosphorus, but so far there is no significance to the history of life on Earth or elsewhere in the universe, but there is significance in expanding our perceptions of what life could be like on Earth or elsewhere in the universe.
Yeah, I don’t think they’re suggesting a separate origin of life. I’m not sure whether they “trained” the bacteria to use arsenic or whether they cultured already-extant arsenic-using bacteria (I missed some of the early press conference), but you’re right, the big deal is expanding what we perceive as habitable whether on Earth or another planet.
As it says in the good book (paraphrased), A man does not live on phosphorus alone…
“Bacteria taken to the lab showed signs of successfully incorporating arsenic into their structure, after an artificially-induced lack of phosphorus.” This is in no way a fundamentally different organism. The bacteria has just evolved. Phosphorus is in the same column of the periodic table as Arsenic, and therefore has many similar properties. It would interesting to know the extent of which life could change, and also how the bacteria incorporated the arsenic into its cells.
So basically there is no evidence of a separate origin of life, but an environment was created to encourage bacteria to use Arsenic instead of Phosphorous? I guess it shows at the least that DNA is more adaptable then we thought.
Exactly. It’s still a cool result, but there was not separate origin of life and these bacteria don’t even use the arsenic in the wild if they can help it.
Essentially this opens the door up to as what other elements within the DNA polymer could be substituted if and when necessary?