Tag: Mono Lake

New research points toward "no" on arsenic life

By Phil Plait | July 9, 2012 11:56 am

In December 2010 a team of researchers, with NASA’s blessing, announced a truly remarkable result: bacteria that lived in California’s Mono Lake not only thrive in the arsenic laced water, but have incorporated arsenic into their biophysical processes. This was a big deal, since it wasn’t thought that this was possible (while arsenic has similar properties to the biologically-necessary element phosphorous, replacing one for the other had never been seen before in nature).

However, the team found their findings immediately under fire by other biologists. Here is my initial report on the press conference announcement, and here’s my followup after severe doubt had been cast on the findings, and a third article from a few months later. Basically, the team’s methods, analysis, and results were found to be lacking, and two other groups of biologists started up their own investigation to replicate the research.

Today, Science magazine published the results. Arsenic? Nope. One team found that while the bacteria thrive in arsenic-rich water, there must be some phosphorus present for it to live (indicating the cells had not replaced As with P). The second team found no evidence that arsenic had been incorporated into the cells’ biochemistry.

This is disappointing but not unexpected news.

When NASA held the press conference, a lot of media – including me – were very excited. We trusted NASA that the work had been vetted by other scientists and was legit. While I think the work was done honestly – that is, the research team didn’t cheat or anything like that – it’s looking like they jumped to their conclusion, and the initial peer review process didn’t work as it should have.

But there’s more to it than this. The members of the original team are sticking by their results, saying that not finding something may not indicate it’s not there – in other words, the followup research may have missed the arsenic. While that’s possible, it comes across as stubbornness in the face of contradictory results. That is simply an interpretive opinion by me, but it does seem odd that they claim the new results actually don’t refute their original findings. It looks to me (though I’m no biologist) that they certainly do.

[UPDATE: Here’s a good article by my pal Dan Vergano at USA Today about this, and he also got great quotes from both the original researchers and the other teams.]

Discover Magazine’s The Loom blogger Carl Zimmer – who has always been very skeptical of the results – live-blogged this new announcement, which makes for fascinating reading. There are some great quotes in there, and it’s worth your time to read through. DM’s 80 Beats blog also has relevant links about all this.

There are several lessons I think we can pull from all this:

1) The scientific process works, but there’s friction with the journalistic process. Of course, we’ve known that for a while!

2) Just because there’s a press conference, and just because it’s backed by NASA, doesn’t mean the results are true. That’s a hard-won thought for me, but one I take seriously.

3) The thing we shouldn’t forget: all the biological research teams do agree that the bacteria in Mono Lake actually do thrive in those arsenic-heavy waters!That itself is an important scientific result. While those bacteria may not incorporate the poison into their own biochemistry, it shows again that life can adapt to extremely difficult and even previously-thought toxic circumstances. The ramifications for astrobiology (finding life on other planets) are still important, and this gives us strong and critical insight into the very chemistry of nature itself.


Related Posts:

NASA’s real news: Bacterium on Earth that lives off arsenic!
Independent researchers find no evidence for arsenic life in Mono Lake
Arsenic and old posts
Arsenic and old Universe

NASA's real news: bacterium on Earth that lives off arsenic!

By Phil Plait | December 2, 2010 11:12 am

[UPDATE (Dec. 7): The research outlined below is under very heavy fire from other biologists. I’ve written a follow-up post about it.]

[Update (13:30 MT Dec. 2): I misunderstood a part of this research dealing with arsenic when I read the journal paper, which was made more clear during the press conference. I have corrected the relevant text below, and struck through the old text. Hope this doesn’t confuse anyone, and sorry about that!]

NASA scientists announced today an incredible find: a form of microbe that apparently evolved the ability to use otherwise toxic arsenic in their biochemistry!

First off, just to be straight and to dispel the rumors: this is not aliens on Titan, or Mars, or anywhere else. This bizarre life form was found right here on good ol’ Earth. And don’t be disappointed: this is still pretty cool news.

Here are the critters in question:

bacteria_arsenic

Note the scale; a typical human hair is 100 times thicker than these beasties.

DM blogger Ed Yong of Not Exactly Rocket Science has written an in-depth and detailed account of all this as well. Highly recommended!

The bacteria (technically, the strain GFAJ-1 of Halomonadaceae) was found in Mono Lake, an extremely alkaline and salty lake in California near the Nevada border. And I do mean salty and alkaline: it has about twice the salt of ocean water, and has the incredible pH of 10 (neutral water has a pH of 7, and the pH scale is logarithmic; this means the lake water has the same alkaline strength as commercial antacids). Worse yet, the lake has a high concentration of arsenic, a deadly poison to many forms of life (including us). This makes the water toxic for most living creatures as we know them; for example there are no fish in the lake. However, there are algae, shrimp, and other such flora and fauna.

… including these new microbes. Dr. Felise Wolfe-Simon found them in the mud around the lake, and discovered that not only do they happily live with the arsenic that when subjected to high levels of arsenic in their environment, they actually incorporated it into their biochemistry!

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