NASA Confirms Discovery of Organism With Phosphorus-Free DNA

GNUALMAFUERTE writes "As we mentioned before, NASA's Department of Astrobiology had an important announcement to make today. It looks like Gizmodo was right. You can watch the presentation online right now. It looks like the bacteria in question uses arsenic as a phosphorus replacement in its DNA."

Not Phosphorus-Free

[Elder Entropist]

It replaces MOST phosphorus atoms with arsenic, but not all.

Not phosphorus free, not just DNA.

[Confusedent]

It wasn't phosphorus free, in fact they hadn't confirmed how much of the phosphorus had been substituted with arsenic, but they did mentioned it was not 100%. They also mentioned it was more than just DNA (ATP was also mentioned, although they implied more).

real info

[burris]

According to this NYT article [nytimes.com] this is a normal earthly bacterium that, when placed in an environment full of arsenic, started swapping arsenic for phosphorus. It's not a totally new form of life unrelated to what we know.

Gizmodo was not right

[commisaro]

The Gizmodo article, like most of the speculation, was largely overblown:

NASA has discovered a completely new life form that doesn't share the biological building blocks of anything currently living in planet Earth, using arsenic to build its DNA, RNA, proteins, and cell membranes. This changes everything.

That is not the case. The DNA is largely the same, except that phosphorous has been exchanged with Arsenic. Don't get me wrong, this is still a hugely interesting discovery, but it was implied during the pre-conference speculation that this was an entirely separate instance of abiogenesis, and that is simply not the case, unfortunately.

Re:Not Phosphorus-Free

[Mindcontrolled]

Well, as much as anything is carbon based, yes. We are carbon-hydrogen-oxygen-nitrogen-sulfur-phosphorus-based, this one is carbon-hydrogen-oxygen-nitrogen-sulfur-phosphorus/arsenic-based. That still makes for a major metabolic difference, but it is still biologically related to us. Same tree of life. Still way cool, though.

Re:Hardly deserves the "New Life" headline..

[andrewd18]

This wasn't "bred" or modified by the scientists from an existing bacterium, it was occurring naturally in Mono Lake and was transported to the lab for concentrated study. That was the second-to-last question answered in the NASA TV broadcast.

Re:real info

[blair1q]

But it sort of is.

We've always ignored the chances of life on extraterrestrial bodies with significant levels of arsenic on the empirically founded theory that arsenic doesn't work in place of phosporus in living systems.

So while this is a lifeform we already knew about, it's a different form of life from what we understood.

The question remains, is it possible for DNA to have evolved in an environment rich in arsenic, or would it have had to evolve in an arsenic-free environment, and just happen to have enough integrity once it's formed to tolerate the replacement of phosphorus atoms with arsenic atoms?

Re:News flash: NASA discoveres there's life on ear

[Defenestrar]

My thoughts are as follows:

THIS IS BLOODY AMAZING! followed by a little more tempered cogitation:

Arsenate is a triprotic species just like phosphate, each has a valence of +5, and it's directly one period down on the table so available electron shells in ground state will appear very similar. However arsenic possesses filled d orbitals and is about 7% less electronegative than phosphorous - these factors, among others, tend to make arsenate a little more reactive than phosphate which would make it less stable as a backbone of DNA. So if the degree of replacement is as thorough as NASA claims (they said they cultured it with zero phosphorous present - so only trace impurities) the cell has either found a way to strengthen the backbone or has developed an amazing repair mechanism which can deal with frequent DNA damage.

NASA has two summaries here [nasa.gov] and here [nasa.gov].

Astrobiology has an article here [astrobio.net].

And http://www.sciencemag.org/ [slashdot.org]">Science will release a paper later today.

Re:Not Phosphorus-Free

[Mindcontrolled]

From a biochemist's point of view, this is a huge substitution, as phosphate and arsenate compounds do usually not coexist well in organisms, hence the toxicity of arsenic. While "everything is made out of carbon", carbon is the rather boring compound that gives stuff its structure. High-energy-bonds, like formed by certain phosphate compounds, give stuff the energy to actually DO things. The virus defense theory is way off, btw - this bacterium evolved in a high-arsenic environment, so this is way more likely a way to cope with the chemical composition of its evolutionary niche.

I just read the Science paper

[Anonymous Coward]

What they did was take samples of bacteria from the mud, and placed them in three conditions. In one condition they kept raising the cells in normal, phosphorous containing substrate, removing a small portion to another phosphorous containing substrate, and repeating for generations. In another they put the cells on a substrate lacking phosphorous or arsenic, and removed a small portion to another empty substrate, and so on. Finally, they put some on a substrate containing phosphorous and arsenic, and kept pulling out small proportions an introducing them to plates higher and higher in arsenic. The serial dilutions eventually decreased the amount of phosphorous to amounts too small to account for the needs of bacteria. Cells grew on both phosphorous and arsenic plates, but they grew better in phosphorous. The arsenic cells had some weird vacuoules which might be helping to stabilize the arsenic based compounds.

They don't know if cells in the wild have this ability or if they evolved the ability over the course of serial dilutions. A simple mass spec can tell that the ones in the wild are not mostly arsenic based though.

Re:Not Phosphorus-Free

[ColdWetDog]

It doesn't appear that they have got to the fun bits yet. Research is pretty much at the overview stage. They appear to have some crystallography data that suggests that the arsenic is bound to the DNA which suggests it's replacing the phosphorus backbone, but I don't see anything that shows the critter has replaced ATP (Adenosine TriPhosphate, the cellular power source) with Adenosine TriArsinate.

Of course, one doesn't expect research to just dump everything out at once, there are many years of digging through this to sort it out.

If arsenic is really powering the bacterium, then it's pretty impressive because the thing seems to grow at about 60% of maximum rate in a phosphate depleted source.

MORONS POSTING ARTICLES WITH NO INFORMATION

[DavidTC]

See, this is why I hate slashdot.

Instead of telling us 'Gizmodo was right', like we all read Gizmodo and keep constantly up to date about what's going on over there, how about TELLING US THE ACTUAL THING THAT HAPPENED.

No, I shouldn't have to follow a link to figure it...there's supposed to be an 'article summary', which, you know, gives some hint as to what happened.

Instead of just saying 'Oh, hey, these other people were right in their guess about a thing which i won't mention that they thought NASA would say.'. Well, woo-fucking-hoo. I'm sure we were all on the edge of our seat betting in the 'How correct is Gizmodo?' pool, and they just got a point! Wow! Who cares about actual news events, let's all sit there and count Gizmodo's points, or something.

Timothy, you goddamn fucking moron. It's one thing when the article summary is misleading or just flat out incorrect, but slashdot has now managed to hit a new low where the article summary doesn't even exist.

Link to Video of Press conference

[Danathar]

I captured and converted it to mp4 format for anybody that wants to view it.

http://www.wuala.com/danathar/public [wuala.com]

file is nasa.mp4 (it's the only one on that page)

Re:First

[mcgrew]

Actually, they DID discover a new life form. They [nasa.gov] didn't actually coax an existing bacteria to "use phosphorus". Instead, they discovered an existing organism that can use arsenic in its DNA and RNA rather than the phorphorus other life on earth uses.

Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur are the six basic building blocks of all known forms of life on Earth. Phosphorus is part of the chemical backbone of DNA and RNA, the structures that carry genetic instructions for life, and is considered an essential element for all living cells.

Phosphorus is a central component of the energy-carrying molecule in all cells (adenosine triphosphate) and also the phospholipids that form all cell membranes. Arsenic, which is chemically similar to phosphorus, is poisonous for most life on Earth. Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate.

The newly discovered microbe, strain GFAJ-1, is a member of a common group of bacteria, the Gammaproteobacteria. In the laboratory, the researchers successfully grew microbes from the lake on a diet that was very lean on phosphorus, but included generous helpings of arsenic. When researchers removed the phosphorus and replaced it with arsenic the microbes continued to grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new GFAJ-1 cells.

The key issue the researchers investigated was when the microbe was grown on arsenic did the arsenic actually became incorporated into the organisms' vital biochemical machinery, such as DNA, proteins and the cell membranes. A variety of sophisticated laboratory techniques was used to determine where the arsenic was incorporated.

Re:Neat, but...

[c6gunner]

It wasn't "political based bashing", it was a joke at the expense of David Icke and his weirdos. And it was damn funny, too.

Re:Not Phosphorus-Free

[robotkid]

Makes me wonder if this is an organism which has adapted to tolerate the damage from arsenic which would kill us.

This organism, almost certainly not. Most of these extremophiles are miserably slow growers (the doubling time was ~2 days vs 20 minutes for E. coli), so unless there's a niche somewhere in your body that allows the extremophile's adaptations to be a major advantage, it would never gain a foothold in your body as the many strains of bacteria we symbiotically live with will outcompete it for resources.

But as to the more general question of whether any dangerous extremophiles exist out there - this is a recurring topic of speculation (over beer) amongst those that work with pathogenic microbes. Consensus seems to be that it's not impossible that an extremophile such as an archaea, or, in this case, a protobacteria could potentially be an opportunistic pathogen as well, but we haven't found one yet so it's probably not a common occurrence. The organism in this press release is a distant, distant cousin of helicobacter Pylori, an acid-loving bacteria which causes ulcers and is linked with gastric cancer, so it's not insane to think it could happen. Just unlikely.

Re:Not Phosphorus-Free

[Anonymous Coward]

The Science paper states that the organism creates vacuole like structures that might provide a hydrophobic environment for the DNA to reside. These structures are not unique to this organism. This would protect the DNA backbone from hydrolysis since exposure of water to the arsenic esters would be decreased.