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

Comments (26)

  1. Daniel J. Andrews

    It’s been a fascinating journey following Dr. Redfield’s live science work as she blogged on each stage of her work as she tried to replicate the original findings. A pity this isn’t done more often for experiments that are conducive to live-time blogging. Can you imagine following Dr. Richard Lenski’s work on bacteria? Talk about cliff-hangers in science and then having to wait while he tried to reconfirm his results by restarting different generations to find where the first mutation occurred. I did like Carl’s live-blogging of the talk by Dr. Redfield. Sure wish I could have been there–maybe there will be a video put up some time.

  2. Jason

    Third paragraph: Don’t you mean “replaced P with As”?

  3. Blargh

    Just because there’s a press conference, and just because it’s backed by NASA, doesn’t mean the results are true.

    That first part can’t be emphasized enough! There’s a reason the phrase “science by press conference” was coined. If it isn’t something revolutionary or an anticipated result of a well-known study, press conferences should quite often make you suspicious.

    @ Daniel J.
    Indeed it has been! The problem is, as usual, the journals – the slightest hint of disclosure beforehand can be enough to make them reject your work. So this is a victory for science in two ways: a validation of the scientific process and, hopefully, a precedent for more openness. If a study so extensively covered live as Rosie Redfield’s can be published in Science, it can hopefully lead the way for others to start opening up as well.

  4. Nentuaby

    I love that Vergano characterized it as “a case study in how science corrects its mistakes.” Not a Blow to the Field of microbiology, not Deep Rifts In the Scientific Community, a case study in self-correction. There’s nothing like a science writer who actually gets it.

  5. MadScientist

    For me it’s not disappointing news at all; it affirms that our understanding of the cell is good enough to say outright that FW-S’s claims were silly. What we see here are the results of scientists doing proper tests to demonstrate that the GFAJ-1 paper was bunkum. Science works – just not necessarily the way some people would like it to. More precisely, in this case people set out to demonstrate what the results may be if the experiments were done with due care; the aim is not explicitly to produce results that discredit the publication in `Science’, but I doubt anyone involved would have believed the results could be otherwise. Rosie Redfield did an excellent job of explaining what was wrong and also managed to find time to carry out experiments to defend her statements. The GFAB-1 paper is done to a cinder. As for `Science’ – it’s way overrated (same goes for `Nature’).

  6. Didn’t NASA back your favorite movie, Armageddon? They backed Space Cowboys. Now, i understand that movies aren’t science. But NASA has taken a credibility hit, IMO.

    There’s been plenty of back-and-forth on alh84001. But we’ve done lots more work with the new microscopes since they came out. Is there any consensus yet?

  7. noen

    Motivated reasoning is a powerful thing.

  8. Torbjörn Larsson, OM

    I think the science is pretty clear.

    I can’t see what Wolfe-Simon will come up with, the original response when she was criticized was the same one of cell-death. Which I believe at least the Vancouver group has controlled for, IIRC.

    It is unclear if from the linked article that the emailed Wolfe-Simon gets support from her original team, she has been severed and not supported by them, and her “we” is a generic term.

    On to the the science context in weird politics:

    I don’t think much of this work. It originated by Paul Davies et al taking an interest in astrobiology, and it was sloppy work.

    Davies is a Templeton-funded deist, and his ideas of “a shadow biosphere” is not very biologically likely. The universal common ancestor of all observed cellular and viral life is the best observed fact of all of science, with ~ 10^2000 against multiple ancestors by way of the common genetic code.

    I assume his interest in trying to observe alternate biochemistries derives from the idea that it makes life elsewhere more possible and by that roundabout human analogs more special. ‘Therefore gods exist.’

    But both of these are common biological hypotheses (evolving populations is easy, evolving traits is very constrained – see the uniqueness of the Elephantidae trunk. They certainly has no connection with Davies stated ultimate interests in understanding nature.

    - But while Redfield is to applaud for much (criticism, openness, using arxiv, using web based research), and her results stands for themselves, her motives comes across as unscientific as well.

    She seems motivated by astrobiologists encroaching on her area. Granted, they overstepped here, she knows more of how to do research on bacteria than geochemist Wolfe-Simon and, it seems, the rest of the original team. But I wish she would take the competition, as it were, in good spirit as founded in curiosity in nature.

    #2:

    Nope, it is one of the two new papers, showing that As was not used. (It was sometimes in inadvertently associated with some of the cellular compounds though. I assume the cells, which were swollen in As containing environments, failed to get rid of all of it.)

    #6:

    What I know ALH84001 carbonates are still considered inorganic et cetera.

    If anything the inflated case has been further punctuated as I remember it. A recent article looked at similar martian comets also with PAHs, and found that they were inorganically produced too, in carbonate containing magmas, by looking inside mineral grains.

    #7:

    Ironically, “motivated reasoning” seems like “arsenic life”, not much evidence in favor.

  9. VinceRN

    Three things this shows us:

    1. Scientist are human and suffer from wishful thinking just like the rest of us.

    2. Science works, even when that wishful thinking happens science eventually gets past it.

    3. It is ALWAYS important to be skeptical about everything. Even when NASA puts their name on it.

  10. Torbjörn Larsson, OM

    bacteria in Mono Lake actually do thrive in those arsenic-heavy waters!That itself is an important scientific result.

    But that isn’t much or any of an improvement by evolution. Many salt or ground waters contain high amounts of arsenic, unfortunately. This 2007 survey found that the then record arsenic resistance record was ~ 700 mg/L (as EC50), for Vibrio alginolyticus. That corresponds to ~ 9 mMol/L arsenate @ ~ 75 molar mass for As, which is less than an order of magnitude from the strain GFAJ-1 tolerance of ~ 40 mMol/L.

    Notably is that GFAJ-1 is a Halomonas strain, which are halotolerant or halophilic (salt lovers). Many marine bacteria are therefore arsenic resistant. The same paper has another Halomonas strain at about half the V. alginolyticus tolerance, still less than an order of magnitude from the new strain.

    Also notable is that they found a bacterial strain that was removing arsenic from water to incorporate it in cytosol. “Therefore, the present results obtained in M. communis with its higher resistance and higher accumulation of arsenic contradict the known arsenic-resistant systems, suggesting existence of an as yet unknown arsenic resistance system for this strain.” I saw elsewhere that the GFAJ-1 sequencing reveals some of the known arsenic resistance systems (arsenic efflux pumps et cetera). In comparison, M. communis seems like the odd guy.

  11. RAF

    Completely unrelated…

    So I’m listening to the TV show, How the Universe works, while surfing, and I suddenly hear Phil’s voice!…I look up, and there’s Phil.

    Now I’m trying to figure how I didn’t know that Phil was even on this show….DOH!!

    …and upon further investigation, I see this is on NETFLIX…how in the heck did I miss it on there….DOH!

  12. Dragonchild

    The punchline is that the old research pointed toward “no” as well.

  13. Infinite123Lifer

    Torbjorn Larsson said:

    “10^2000 against multiple ancestors by way of the common genetic code.”

    Could you just write that number out please? My TI-83 just says error

    Jk ;-) I enjoy reading your comments all over the place, I would hate for you to have to spend the rest of your Life typing in vain.

  14. Messier Tidy Upper

    Too much build up and over-hyping of the original press conference with somuch speculation and secrecy meant that a lot of people felt let down when the original announcement was made – then in later days and weeks we learnt that even this wasn’t really accurate.

    Bad media, good self-correcting science, Major example of how NOT to do press conferences and anounce findings.

    Maybe there’s going to be another twist in this story but it seems unlikely. Extremophile microbes living in such arsenic laden toxic waters have been given some extra publicity and are pretty amazing in themselves but this should serve as a cautionary tale of a few things NOT to do.

  15. Wzrd1

    Interesting! I posted THREE times on this subject.
    In common, articles that were not considered objected to, fringe theory, false or even odd in nature.
    Each time, they were in the “Website” area.
    ALL were summarily discarded.

    So, either Wikipedia is forbidden on Discovery sites OR on Phil’s blog OR there is another significant issue here.
    This is simply a test on one theory.
    As As is to P what S is to O.
    I can’t imagine WHO would want to attempt to breathe SO2…

    THIS post worked. So, one must consider a filter against “Website” being Wikipedia articles, of interest, biochemistry of As.

  16. TheBlackCat

    @ Wzrd1: All posts containing links are automatically filtered by Discover Magazine’s spam filter. Phil has to manually approve each one, which may take some time, especially if he is asleep.

  17. MadScientist

    “… the bacteria in Mono Lake actually do thrive in those arsenic-heavy waters!That itself is an important scientific result.”

    Important, yes – but certainly not new. Reports of bacteria in water with very high As concentrations have been in the literature more than 20 years before the GFAJ-1 paper. If I recall correctly, the bacteria of Mono Lake were among the already known As tolerant species. The only new claim (which was wrong and immediately got the biologists enraged) was that the bacteria substituted As for P in its biochemistry.

  18. Rorgg

    >indicating the cells had not replaced As with P

    The other way around, isn’t it?

  19. Tom

    @ Torbjörn Larsson,

    I don’t follow your reasoning about the motivation of Paul Davies. It would seem to me that a person trying to buttress the existence of Gods would want to prove that life on Earth is completely unique (possibly not existing anywhere else in the universe). The possibility that life only started successfully a single time on Earth would seem to support that case more than shadow biospheres that evolved independently. Multiple strains of life on Earth would seem to imply that it is easier for life to start elsewhere. Thus, Earth would no be so special after all. What am I missing?

  20. Nigel Depledge

    Wzrd1 (15) said:

    As As is to P what S is to O.
    I can’t imagine WHO would want to attempt to breathe SO2…

    Probably the same people who like to breathe O3.

    S2 would be the period 3 equivalent of O2. And, IIUC, S2 does not exist.

  21. Nigel Depledge

    I don’t know if it is childish of me to mention this, but here is arsenic’s best organoarsenic compound:
    http://en.wikipedia.org/wiki/Arsole

  22. Jordan

    S2 can exist in a transient form, generated in-situ and then trapped by another chemical intermediate. But you’re right in the sense that it can’t be “bottled” — it’s too unstable.

  23. James

    You make me sad, Phil.

    Just when I thought you were my hero, you’ve become a denialist?

    :’(

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