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.