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