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Discussion in 'Et Cetera, Et Cetera' started by Big Al, Dec 2, 2010.
NASA Finds New Life (Updated with Pictures)
To borrow the words of our Vice Prez, "this is fuckin' HUGE'!!!
I'm not a scientist but I have wonder about something that can live as a result of posionous matter; is that really a good thing?
*YAWN* Old news.
Arsenic to build DNA, that's interesting
That is an interesting comment. I am curious why you had a reaction to that. A poision is nothing more than a chemical compound that is incompatible with an organism's biology. And if the biochemistry of an organism is different enough, then the set of compatible and incompatible compounds for it would be different than other organisms.
Or, to put it another way, one organism's poison is another organism's food.
What interests me is how its DNA will position it in the tree of life. Is it different enough for us to consider it to be "exobiotic"?
In this organism, the arsenic seems to replace the role played by phosphorous. This is not too surprising in some respects since As and P both appear in the same column of the periodic table. They both have a 4 molecule form that has the same tetrahedral shape. As4 and P4 form a pyramid shape with three atoms at the base and one above them.
There are quite a few chemical reactions where arsenic can be substituted for phosphorous. So its not puzzling that arsenic can be used in biochemical pathways.
What is puzzling is why this particular organism is not susceptible to the way that arsenic interferes with the production of thiol which are chemical groups that play important roles on different sites of enzymes. This is the chief reason why arsenic is toxic to most organisms.
One more comment to nudeyorker's question: Arsenic used to be used in a lot of different medicines before antibiotics came along. And it is still used in some cancer treatments. So one man's poison might also be another man's life saving medicine.
Sorry to barrage the thread, but this is an area of great interest to me. I might be restating the obvious, but the "huge" part of this is not that we found a life form that metabolizes arsenic, but that we found the first life form that does it.
What I mean to say is that we did not expect to find an arsenic metabolizing life form so we were not looking for one. The implication is that if we find one life form that is "outside the box" of our expectations here on Earth, we should surely find more.
And this has implications for how we search for life outside of our own planet. We search for life in a lot of different ways besides actually getting soil samples, like we do on Mars. The search usually involves analyzing the spectrum of light coming off of compounds in space or on the surface of planets and moons that we observe by telescopes or space craft.
In other words, we look for the possiblity of life by looking for environments that might support life as we know it. Up until now, we would not be looking for a mixture of compounds that was missing phosphorous but had a lot of arsenic.
This goes for life on Earth, too. This is why some of the articles are referring to the fact that we probably live in the midst of a lot of "shadow biology" that we are not tuned in to yet. So we miss the fact that these forms of life exist at all.
I think the last example of this before the arsenic bacteria would be the prolific life we found around very hot deep sea thermal sulphur vents. Not only did we find life where we did not expect to find it, but life around those vents are now so obvious to our thinking that some suspect that the first life forms may have come about around those vents.
erm, is it definately native? could this be literally alien?
Thank you for the thoughtful and intelligent analysis JustAsking. My only undergraduate 'F' was Organic Chem 110...so this is a realm WAY out of my league. I appreciate you breaking it down.
Yes, it could be literally alien having come to us on a meteorite or something, but we would have know by now with a high degree of certainty. We could tell that by sequencing its DNA and I am sure we have already done that, since the interesting thing about the critter is that it uses arsenic in making amino acids rather than phosphorous.
The reason why we could tell with such certainty is that one of the pillars that support the notion that all life on the planet has descended from a common life form (or forms) is that they all use the same universal genetic code.
Besides the fact that all life on earth seems to use either RNA or DNA as its genetic database, the amino acid combinations that all life uses is also universal. Given that the number of informationally equivalent alternative codes number in the 10^70 (ten to the power of 70), any life form that is not descended from the first life forms on earth would be immediately obvious.
This is because the chances of it using the same unversal genetic code without having descended from the first life forms that earth life did, would be one in 10^70.
So that rules out the possiblity that it fell to earth in a meteorite having evolved independently in some other way that puts it outside the family tree of life on earth.
However, as solid as the notion of common descent is, the question of abiogenesis (the origin of the first life form or forms) is highly speculative. That leaves open the possibility that the first life forms that all life evolved from on earth came from somewhere else having seeded the earth so many billions of years ago. (this is called the "panspermia hypothesis").
And this leaves open the possibility that this critter evolved from the same first life forms that earth life did, but the first life forms themselves lived somewhere else outside of our planet. In other words, the tree of life on earth is intact, but the roots of it are not from earth and this critter shares a very early exobiological common ancestor.
But finally, there is no suggestion that this guy is different enough for that to be a bigger question for this critter than some other life forms on earth. It simply has figured out how to metabolize arsenic instead of phosphorous and it may have done that recently rather than billions of years ago.
After all, we have bacteria that has evolved on its own to eat nylon and other recent created synthetic compounds, so the arsenic trick is not so special to suspect it is an alien.
As I said before, the big story is not that it metabolizes arsenic so much as that we just never anticipated something that. It says more about our limited vision that it does about the uniqueness of this critter.
And it is not that we are suprised by our limited vision, either. There is a field called "exobiology" which is the study of life forms from outside of the earth. You might be say that a field like that is as ridiculous as "unicornology" given that we have no examples of exobiology. But the field is also involved in speculating what other kinds of biochemistry might be possible. Carl Sagan was an exobiologist who did this sort of thing, for example.
As the article in the OP implied, such speculation is important if you want to search for life outside of our planet. We expect that life to have different biochemistry, but lacking knowledge of what that might be, we don't know what to look for in terms of a viable environment or viable signs of that life itself.
What this arsenic critter told us that that this is also true to some extend here on earth. We have life around us on earth that we are not tuned in to be looking for.
But it is not really possible for us to judge if our speculations on other kinds of alien biology are very visionary or very naive. I think the reason why the arsenic critter is getting so much press, is that it demonstrates that we are way over on the naive side of the spectrum rather than the visionary one.
Once we analyzed the mechanism it uses for metabolizing arsenic we said, "Oh, yeah. Why didn't we think of that before?". You see what I mean? We were surprised more by our lack of vision than we were the uniqueness of the arsenic critter.
Finally, I don't want to sound dismissive of this finding as if I know it all. I find it amazing and fascinating but not because it might be alien. I think it deserves all the press it is getting and I think it reminds people how miraculous life is to begin with.
That was a very thorough response J A. Thanks. Though i'm somewhat saddened that i'm not going to see a winged dinosaur flying through the shopping precinct or a poor unfortunate black dude being sucked up the ass of a giant amoeba any time soon....
Thank you! You have given me something new to consider. I looked at it from a different perspective I suppose in that it could perhaps be dangerous if incorporated to live or be cultivated in our atmosphere. It would be interesting to see if the the components that support life here would be toxic to these organisms.
as uninteresting as this sounds it is the best science can come up with. Sadly it cost us hundreds of millions of dollars,probably. When are they going to get those space ships built I ordered.
I ask the same thing, i have a pretty fair idea that from a UK perspective, the little cash we spend on a space program is currently being spent on an enquiry....... 'How, when the US can come up with cool names like Endeavour, Discovery, Challenger and Voyager etc etc, we come up with 'Beagle'?.
Not so fast. Endeavor, Discovery, etc are really cheesy but hollow names that are supposed to be inspiring. Beagle, on the other hand, was the name of that great explorational vessel that Darwin sailed on when he made the discoveries that led to his theory of evolution.
It also honors your countryman. Go with Beagle and be proud.
Damn your intelect! :wink:
I want cheesy and hollow!
Reread some of your old threads!:redface:
So the gloves come off.... :biggrin1::biggrin1::biggrin1:
Doesn't this pretty much prove that evolution is real?