I’m not being hyperbolic. This is something that will have a dramatic impact on biology, the search for extraterrestrial life, and evolutionary thought:
Hours before its special news conference today, the cat is out of the bag: NASA has discovered a completely new life form that doesn’t share the biological building blocks of anything currently living on planet Earth. This changes everything.
At its conference today, NASA scientist Felisa Wolfe-Simon will announce that NASA has found a bacteria whose DNA is completely alien to what we know today. Instead of using phosphorus, the bacteria uses arsenic. All life on Earth is made of six components: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. Every being, from the smallest amoeba to the largest whale, shares the same life stream. Our DNA blocks are all the same.
But not this one. This one is completely different. Discovered in poisonous Mono Lake, California, this bacteria is made of arsenic, something that was thought to be completely impossible. While Wolfe-Simon and other scientists theorized that this could be possible, this is the first discovery. The implications of this discovery are enormous to our understanding of life itself and the possibility of finding beings in other planets that don’t have to be like planet Earth.
Now the real fun begins. Quite literally, this bacteria is alien life — it is a species whose line has diverged from every single other species on Earth that we’ve found. But when did it diverge? A million years ago? A billion? Or did it diverge at all? Is it a part of a completely different lineage, of arsenic-based lifeforms that were outcompeted by us? Or is it an example of abiogenisis, a literally new lifeform that has sprung up out of nothing? Or did it find its way here on a rock from another world, from Titan or Mars, and find a resting place where it could survive? Are there more species like it, hiding in areas that are poisonous to species like ours? Or is it unique on this planet? In this solar system? In the universe?
No matter what, it presents something exciting and new. Life on other planets is likely to be based on different biochemistry than ours; DNA is our coding system not because it’s the best or only system that works, but because it’s the one that won the dance of evolution. This species represents something alien to us — a species that is not a sibling, like whales or platypuses, nor a cousin, like spiders or earthworms, nor even far-flung relation, like pine trees or E. coli. It’s a species that is, for the first time, completely different than us. And that makes it perhaps the most important thing we’ve ever found.
This New York Times piece says that the bacteria was trained to subsist on arsenic, and “swapped atoms of phosphorus for… atoms of arsenic.”
A look at current news reports reveals that these bacteria, while living on arsenic, are also clearly descended from normal earth life, not least because the NASA scientists took more ordinary bacteria and fed them only arsenic with no phosphorus for a while.
Sadly much of the journalism on this appears to be even more horrid than the usual sad state of science journalism, and sadly, Jeff, it looks like you saw one of the more overblown reports on the matter.
It’s not the discovery of the millennia. It’s not alien life, or life that has nothing to do with regular earth life. These are Earth bacteria, closely related to many other more normal bacteria, that can thrive in an environment with tons of arsenic, as found in certain salt lakes.
The new discovery is that these bacteria can actually incorporate arsenic into their proteins and DNA, using it in place of phosphorous. Phosphorous is one of 6 elements that the textbooks say is essential to all Earth life. It’s part of APT, the cellular engine that extracts energy from food, it’s part of DNA, it’s part of a lot of things. That these bacteria can make APT and DNA using arsenic instead of phosphorous is very interesting and cool news that means all those textbooks are going to have to be rewritten, but it isn’t the most earth-shattering discovery of all time.
My source for this kind of thing is the science blogosphere rather than newspapers or magazines. CF http://blogs.discovermagazine.com/notrocketscience/2010/12/02/mono-lake-bacteria-build-their-dna-using-arsenic-and-no-this-isnt-about-aliens/ for more details.
It’s not a case of independent origins of life – it’s a member of the existing bacterial class Gammaproteobacteria, family Halomonadaceae. Given the lake has only been present since the last Ice Age, it’s probably fairly recent, too.
The discovery is important, don’t get me wrong, as it shows that under the right evolutionary and chemical conditions, not only can other elements function in place of the usual ones, but organisms can evolve to ‘switch’ functions or even utilize both.
But all of this “MOST IMPORTANT THING EVAR!!1!eleven!!” crap is just overblown. Every damn time some microbe is found in an extreme environment or doing something chemically interesting (breathing with sulfur, etc.), the media jumps all over it, screaming about aliens and how this changes everything we’ve ever known. 3 months later, everyone’s forgotten, a few more years pass, and yet another odd bug shows up, ad nauseaum.
I’ll bet my car that of the first 100 inhabited worlds we find, zero use arsenic as a major component of cellular metabolism. Why? It’s *rare*. Any organism using arsenic would rapidly be out-bred by competitors using more common elements. And the fact that it’s rare is largely due to how planets form – there’s not going to be an Arsenic-World.
Honestly, I’m just annoyed at things being blown out of proportion. It’s important, but all it does is expand the already-known concept of “microbes can do weird shit with their metabolisms” a bit.
I have to agree with the other commenters – you have been a victim of hype. If you have a university (or other) subscription to Science, you can read the original article here. To summarize, this bacterium is very peculiar, but it’s a fairly ordinary member of a large family of halophile bacteria. Arsenic is chemically similar to phosphorus – in fact that’s why it’s poisonous, because our metabolisms confuse the two – and some organisms that could tolerate it were known. But these researchers were looking for an organism that could live on only arsenic, without phosphorus. So they took a random soup of bugs from a high-arsenic environment, and grew it on media with less and less phosphorus and more and more arsenic. Gradually almost all the bacteria died, but one strain from the original soup survived. That’s the one they did their study on.
This bacterium mostly uses arsenic instead of phosphorus, but they weren’t able to get rid of all the phosphorus – the bug hoarded all the phosphorus it could scavenge from trace impurities in the reagents. But there was only a tiny amount (less than a thirtieth than they found in the same cells given all the phosphorus they wanted). And they did a number of tests that seem to show that the arsenic really is getting substituted for phosphorus, particularly in the DNA.
So: a weird bacterium, capable of using a peculiar biochemistry. But not alien, not evolutionarily peculiar, and not an example of researchers modifying an existing organism. Evolutionarily, it’s an example of existing life adapting to do something we hadn’t known was possible. It’s of interest to people looking for extraterrestrial life because it means that phosphorus isn’t an absolute requirement. But as Mokele says, it’s not like phosphorus is scarce.
As for the publicity side of things, well, I’ve been on the other end of the press release machine (for a much less exciting discovery). You struggle to keep the press releases honest, and the publicity folks struggle to make them as exciting as possible. And then the reporters get a hold of them and throw away all your careful qualifications anyway, and inject their own imagination. So I’ve learned to go as close to the primary source as I can – read the original paper if possible, read a blog post from the author, or at least a scientist in the same area, if not. It’s a shame the raw papers are so often behind paywalls; they’re not usually as impenetrable as one might expect, and they generally give the whole story.
[ETA: Just to be clear, I’m not knocking the folks who wrote either the press release or the article I linked to; in fact, they were about the best I saw. It’s the system as a whole that encourages hyperbole and fluff over science. -A]
Because of the similarities of their chemical properties it’s long been suggested that arsenic could substitute for phosphorous under certain biological conditions. Looks like Moro Lake has those conditions, and NASA found a way to take advantage of that. This is pretty cool.
It’s also illustrative of typical science reporting in the MSM. A team of scientists comes up with a discovery. They report it, being careful to note the conditions and limitations on what they did and what conclusions can be drawn. The MSM then ignores the the limitations and conditions the scientists noted and print whatever will inflame the public’s imagination and, perhaps, confirm any pre-established ideas in the reporters’ or editor’s minds. Of course, given the sad state of science education in this country, perhaps I shouldn’t ascribe to malice that which can be adequately explained by ignorance. But whether it’s scientific work on biology, human sexuality, climate, or anything else, you just can’t trust scientific reporting in the MSM.
Damn. Bunch of party-poopers on this thread.
Life on other planets is likely to be based on different biochemistry than ours; DNA is our coding system not because it’s the best or only system that works, but because it’s the one that won the dance of evolution.
Well, not really.
Life on other planets MIGHT be based on different biochemistry than ours. But there’s no reason to assume that it will be, and one mildly convincing reason to think that it won’t be. Even this result (which IS tremendously exciting for biology) only indicates that alternative pathways are feasible; it doesn’t mean they’ve arisen anywhere in the state of nature.
It’s a bit like driving from New Mexico to to Montana. Yes, there are alternative routes to I-25; thousands of them, or billions if you’re willing to go far enough out of your way. The routes can be found, even if they are literally archaeological remnants of previous routes in some cases. But they’re all somewhat- to much- less efficient, which is why I-25 carries 99.99% of the traffic.
The odds are pretty good, if not a lock, that in fact our method of chemically organizing life IS the best way possible.I’d be willing to bet that the arsenic-acclimated bacteria that can use arsenic, are less energy efficient in doing so than they would be if they had phosphorus instead.
What this finding does indicate, and where it will have an impact on biology and exobiology, is that biological systems may have capabilities in reserve that are not obvious. We know far less about life than we thought we did, and need to have a more open mind about many possibilities of organisms.
The mildly convincing reason to think that life on Alpha Centauri III will have a similar structure to life hear on Sol III? Panspermia, which still is in the lead for nontheistic explanations of life. It’s hardly a proven theory but it has its adherents and is more intellectually satisfying than the “it just happened to happen here” theory of genesis.
@8:
You don’t have to bet; the researchers tested this, and they are less efficient. What’s more, they cling desperately to every trace of phosphorus they can scavenge. So yeah, it looks like phosphorus is a better choice, at least given our biochemistry.
We shouldn’t assume too strongly that alien biochemistries work like ours, though; we really don’t have any idea which aspects of our biology are the way they are because they’re the best possible and which are historical artifacts. For example, amino acids are normally all left-handed, while sugars are normally all right-handed. As far as we can tell, the mirror chemistry would have worked just as well, and it seems likely (though there is debate about this) that the handedness of our amino acids and sugars is an accident of history. What’s more, the biochemistry that’s optimal for one set of conditions (21% free oxygen, ~30 Celsius, say) is not at all optimal for other conditions (no free oxygen, 70 Celsius, say). On Earth, we see different biochemistries for these settings (aerobic metabolism versus anaerobic metabolism). We also see plenty of examples of convergent evolution, places where terrestrial life came up with very different solutions to the same problem – the classic example is cephalopod eyes and human eyes, which do the same thing but work rather differently. So I personally expect that extraterrestrial life would be different in all sorts of ways from terrestrial, and I think it would be very interesting to examine those differences.
Here I have to disagree with you. Panspermia, as an idea, has been around for a while. But it doesn’t solve the problem of how life originated. What it says is that life originated somewhere, and was carried across interplanetary and/or interstellar space to the Earth. One still needs to somehow explain how life can have arisen somewhere. If we found that the spontaneous formation of life were possible but unlikely – too unlikely to have happened in the few-hundred-million-year window available on Earth – then panspermia might be a plausible explanation. But even if only one planet in a million would give rise to life, well, even if panspermia is impossible, the weak anthropic principle just means we’re living on that one planet in a million.
That said, panspermia at least within the solar system is not totally outrageous as an idea – we have found meteorites from Mars here on Earth, after all. So almost certainly some hunks of the Earth have fallen on Mars. And if some of those hunks contained bacteria, which survived the long freezing and irradiation followed by a blazing crash-landing, terrestrial bacteria could have wound up on Mars. If they fell in congenial conditions, well, perhaps they could have flourished. Who knows?
OK, not more plausible. Cooler.
Totally on-topic:
http://xkcd.com/829/
Oh, I don’t know. From the press reports I’ve seen and photographs of the organism I think there is a definite resemblance to Klaatu. Gort will shortly vaporize the above doubters.
Our biochemistry didn’t evolve purely by happenstance. We are carbon-based and have particular kinds of structures because of the physical and chemical properties of various molecules and the constraints of the 3 laws of thermodynamics. Sure, life can and likely did evolve in a great many places, and there’ll be variations from place to place. But I’d be very surprised if complex life elsewhere doesn’t end up having a whole lot more similarities than differences compared to ours.
we have found meteorites from Mars here on Earth, after all. So almost certainly some hunks of the Earth have fallen on Mars.
Don’t forget that we are deeper in the Sun’s gravity well than Mars is and have a deeper gravity well of our own to boot. Debris that escapes Mars is a lot more likely to fall in towards the Sun – and thus cross our orbit and possibly hit us – than debris from a collision with Earth is likely to a) escape Earth, b) go up the gravity wells to Mars’ orbit and c) be captured by Mars. I’m not saying it’s impossible, but it’s a lot less likely.
The discovery is important, don’t get me wrong, as it shows that under the right evolutionary and chemical conditions, not only can other elements function in place of the usual ones, but organisms can evolve to ‘switch’ functions or even utilize both.
I find this encouraging. In the sense that possibly, even if we humans mess up the earth so badly that life-as-we-know-it can’t make it, life-as-we-know-it can become life-different-from-what-we-know, at least on the bacterial level.