NASA makes an unbelievable discovery.

[DarklingAlice]

And I mean that. I literally do not believe this (yet).

Apparently, NASA scientists went microbe hunting and brought us back a peculiar little organism from a lake in California. They are swearing up and down that this bacterium can substitute arsenic for phosphorous in all of its biological processes and molecules (up to and including DNA).

Life is mostly composed of the elements carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. Although these six elements make up nucleic acids, proteins, and lipids and thus the bulk of living matter, it is theoretically possible that some other elements in the periodic table could serve the same functions. Here, we describe a bacterium, strain GFAJ-1 of the Halomonadaceae, isolated from Mono Lake, California, which substitutes arsenic for phosphorus to sustain its growth. Our data show evidence for arsenate in macromolecules that normally contain phosphate, most notably nucleic acids and proteins. Exchange of one of the major bioelements may have profound evolutionary and geochemical significance.

NASA's announcement:
http://www.nasa.gov/home/hqnews/2010/dec/HQ_10-320_Toxic_Life.html

The science behind it:
http://www.sciencemag.org/content/early/2010/12/01/science.1197258

This is probably a case of selective usage and clever metabolism (or laboratory error), but we will just have to wait and see. I'll be going over the paper and its supplemental material tonight, and if I see anything remarkable I'll make note of it. Who knows? The might even be right.

EDIT: Once again it looks like I am going to have to be ranting against the way publicists and media distort science. But a little later. tl;dr version: This is a really cool extremophile. The significance of this discovery? Extremophiles are really cool. Wait, didn't we already know that? <_<

[applesauce]

Things living on arsenic?? Unheard of.

Maybe life does exist out there after all...

[Brandon]

The part that Im skeptical about is they claim they found it in California. If this were Papui new genui or the amazon or some other unexplored area of the world I wouldnt be so skeptical. As is, I have a hard time buying that this came from California though. The US is heavily explored and heavily documented. Could something unknown have existed here? Yeah I think its possible, but highly improbable

However, now we come to another issue. A lot of people are claiming its some kind of alien microbe but to my knowledge theres no evidence of that. If the microbe really exists (I have my doubts about it at this point in time) then I think it is more likely that it is earthborn and just something new

[DarklingAlice]

Okay, let's break this down. There has been a ton of hype over this, and the hyperbole is flying wild.

"Alien life has been among us all along, according to new biological findings announced by NASA Thursday."
-FOX News

"A strange, salty lake in California has yielded an equally strange bacterium that thrives on arsenic and redefines life as we know it, researchers reported on Thursday."
-MSNBC

"One of the basic assumptions about life on Earth may be due for a revision thanks to research supported by NASA’s Astrobiology Program."
-NASA

Even the abstract is a little misleading:

Life is mostly composed of the elements carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. Although these six elements make up nucleic acids, proteins, and lipids and thus the bulk of living matter, it is theoretically possible that some other elements in the periodic table could serve the same functions. Here, we describe a bacterium, strain GFAJ-1 of the Halomonadaceae, isolated from Mono Lake, California, which substitutes arsenic for phosphorus to sustain its growth. Our data show evidence for arsenate in macromolecules that normally contain phosphate, most notably nucleic acids and proteins. Exchange of one of the major bioelements may have profound evolutionary and geochemical significance.

Perhaps  only one quote stands out from this storm in all of this as having an air of truth:

“I have no idea how they’re doing what they’re doing,”
-Felisa Wolfe-Simon, lead author.

So what do we actually know? And what does it mean?

What We Know
1. If you take GFAJ-1 out of its environment (which does include phosphorous) and put it in the lab on an As+/P- medium, it will still grow. However this growth is significantly less than growth either a rich medium or on an As-/P+ medium. (growth on an As+/P- medium also involves an initial dieback, which might be explained by the time it takes for vesicle formation, see below).
2. Analysis reveals that at this point the cells will be .19 (+/-.25)% As and .019 (+/-.0009)% P by dry weight (~7.3 As:P ratio).
3. NanoSIMS analysis reveals As associated with DNA. X-ray absorption data indicate that the presence of As-O-C bonding. It further suggests that certain residues that are usually phosphorylated are arsenylated.
4. The structure of GFAJ-1 changes quite strikingly in an As+/P- media, including the formation of vesicles.

What it Means
1. Most likely, what we are seeing is the actual incorporation of arsenate into DNA and macromolecules much in the same way phosphate would be were it available. That is A) really cool; and B) not at all unexpected. In brief, the reason why arsenic is poisonous to you is that it incorporates where phosphorous should, but these incorporations are highly unstable and wind up crashing your biological pathways. What GFAJ-1 has discovered is a way to stabilize these arsenic reactions. That is probably what the vesicles are for. Since water would hydrolyze the hypothesized bonds, GFAJ-1 shunts it to reservoirs subdividing itself into an area for wet reaction and an area for dry reactions. It is important to note that this is a stress response. It is neither the preferred way nor the most efficient way for the organism to live. It is not an "arsenic-based lifeform" and does not "thrive" in arsenic. It's much more analogous to the way cells begin eating themselves when they starve, or how heat shock induces the transcription of chaperones.

or

2. The arsenic is involved in a phosphate stabilization/salvage pathway that takes that ~.02% phosphorous and makes it go the extra mile in these starvation conditions. The association of the arsenate with DNA is a putative part of this pathway.

It is really too early to say, which of these scenarios is true. Either way we have discovered a cool new biological mechanism employed by extremophiles. But that's pretty much where this begins and ends. This is does not redefine biochemistry. This is not a new form of life (we know many other members of the Halomonadaceae family, this may be a new genus, and is a new species). At the moment, we don't even know if it can survive without a minimum trace amount of phosphorous (and we do know that it survives much better with phosphorous, and preferentially uses it if available).

So it is cool. Very cool. But it is not, by any stretch of the imagination, what it is hyped to be. Once again, the media and publicists make promises without a firm grasp of the science behind them.



Obviously the source for all of the above is:
A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus

    * Felisa Wolfe-Simon,
    * Jodi Switzer Blum,
    * Thomas R. Kulp,
    * Gwyneth W. Gordon,
    * Shelley E. Hoeft,
    * Jennifer Pett-Ridge,
    * John F. Stolz,
    * Samuel M. Webb,
    * Peter K. Weber,
    * Paul C. W. Davies,
    * Ariel D. Anbar,
    * and Ronald S. Oremland

Science 1197258Published online 2 December 2010 [DOI:10.1126/science.1197258]


EDIT: Brandon, get a basic education in microbes. There are more prokaryotes in your body alone than there are eukaryotic cells. They undergo mutation at a higher rate, and they have a generation time orders of magnitude below any of us. New species rise and fall daily. Worldwide. We haven't even put a dent in cataloging the number of extant microbe species in America (nor will we, because it is generally unprofitable unless they do something interesting).

And as covered above, no one actually involved with this believes it is an alien microbe. The phylogeny is fully published in the supplemental materials to the article.

[Oniya]

So, in a way, it's like a creature with a normal hemoglobin system of transporting oxygen somehow adapting to be able to survive CO exposure (which normally latches on where the O₂ molecules would and crowds them out).  The normal configuration is still far preferable, but the normally toxic configuration is no longer incompatible with survival.

[DarklingAlice]

The normal configuration is still far preferable, but the normally toxic configuration is no longer incompatible with survival.

Exactly! Which is awesome, but a fairly common strategy for extremophiles. This is what they do, find a niche that will kill of competition and come up with a way to survive in it.

As a sidenote, this isn't even the weirdest one of them either. I think that Deinococcus Radiodurans still holds first place.

[mystictiger]

Presumably there must still be a limited amount of Phosphorus floating around in this environment. Or is there an alternative to the various phosphate coenyzmes like cAMP and ATP?

[Shjade]

Exactly! Which is awesome, but a fairly common strategy for extremophiles.

Every time I see you write "extremophiles" I can't help but picture some kind of anthropomorphized bacterium in mid-air at the top of one side of a half-pipe grabbing his skateboard with one hand (err...cell wall? membrane?) and flashing some kind of gang sign with the other, all of this floating above XTREME EVOLUTION, as some kind of microbial skate park advertisement poster.

Oh, and a little speech bubble has the skater bacterium shouting, "Rad!" And it's wearing a sideways baseball cap.

I know, I'm a bad person. v.v