Arsenic-eating microbe

[magicsiew]

Hi, I read an interesting article, about bacteria that eat arsenic. Here is the link of that paper.

http://www.nature.com/news/2010/101202/ ... 0.645.html

However, it doesn't state what kind of bacteria is it? Anyone has any idea on what species is this? Or at least genus?

[JackBean]

and they wrote it was in Science...

[canalon]

More detail here. Truly fascinating. And quite the example of an ability that could be dubbed macro-evolution if there was such a thing.

And they belong to the Oceanospirillales. So definitely not some weird unique case, a real case of evolution of a fundamental change within a known group.

[Awol]

So what are the arsenic equivalents of ATP and DNA/RNA?

[canalon]

ATAs I guess.
The As atom is very similar to P. But the final structure are less stable (see the link I posted). So also completely new molecules are created, they are still very close to the original (P-containing) one. Unlike what is implied in another thread on the same subject, it does not appear to be a completely new biochemistry, just the same old structure with other atoms. Still fascinating and a demonstration that some radically new things can evolve, but this is not yet a new independant tree of life

[magicsiew]

Thanks Canalon, the link provides a lot more of information.

[Awol]

So it just uses Arsenate ( AsO4^3− ) instead of Phosphate ( PhO4^3- ) ?

This is fascinating stuff, however I cant help but feel we shouldn't be surprised that life had adapted to flourish in more inhospitable environments, it has a good track record when it comes to that sort of thing

What do you think about the need for the presence of water as an essential medium for life? If you take the Atacama desert for example. No water and not even bacteria in the soil. Life cant seem to get a foothold? Or could the methane liquid/gas atmosphere of planets or moons such as titan serve as a alternative?

[Tranc3r]

This is why cell biology is so fucking amazing, you can't find this stuff by reading the bible.

[biohazard]

What do you think about the need for the presence of water as an essential medium for life? If you take the Atacama desert for example. No water and not even bacteria in the soil. Life cant seem to get a foothold? Or could the methane liquid/gas atmosphere of planets or moons such as titan serve as a alternative?

Here on the Earth water seems to be pretty damn crucial. At least I cannot think of any example a life form that would be able to carry on its metabolic functions in the complete absence of water. But then again, we don't really have liquid ammonia or methane lakes here for life to have a try. Maybe on some other planet or moon this could happen. And my skills in chemistry don't go so far that I could speculate whether life could evolve in a completely gaseous medium - like in an atmosphere of a gas giant or such.

One thing about this ongoing "arsenic-eating" bacterium conversation puzzles me: why are many people now drawing to a conclusion that this means life could have evolved several times on this planet? I mean, it is possible of course, but to me this bacterium looks pretty much like something that has a common ancestor with all other life on this planet, it has just evolved to live in a very unusual environment and apparently in a very unusual way. But surely this has little to do with completely another kind of life form - not even if it had arsenic in its DNA as they claim (which of course would be extraordinary still).

A completely new form of life would surely require something else than nucleic acids as its replicating element, otherwise it would look more like a descentant of whatever was the first nucleic acid-based life form anyway?

[Awol]

Here on the Earth water seems to be pretty damn crucial. At least I cannot think of any example a life form that would be able to carry on its metabolic functions in the complete absence of water. But then again, we don't really have liquid ammonia or methane lakes here for life to have a try. Maybe on some other planet or moon this could happen. And my skills in chemistry don't go so far that I could speculate whether life could evolve in a completely gaseous medium - like in an atmosphere of a gas giant or such.

One thing about this ongoing "arsenic-eating" bacterium conversation puzzles me: why are many people now drawing to a conclusion that this means life could have evolved several times on this planet? I mean, it is possible of course, but to me this bacterium looks pretty much like something that has a common ancestor with all other life on this planet, it has just evolved to live in a very unusual environment and apparently in a very unusual way. But surely this has little to do with completely another kind of life form - not even if it had arsenic in its DNA as they claim (which of course would be extraordinary still).

A completely new form of life would surely require something else than nucleic acids as its replicating element, otherwise it would look more like a descentant of whatever was the first nucleic acid-based life form anyway?

Thanks for you insight. It is truly a thought provoking.

We have already thrown out one rule of biology with the absence of phosphorous in this microbe. Which of the other laws of biology can we get rid of.

For example water is a polar molecule, making other polar molecules soluble in it. This is essential for life on earth as it act as a medium for our cellular chemical reactions could an atmosphere of ammonia or methane preform the same function? In addition to this water exists as a gas/liquid/solid in our atmosphere similar to the moon titan however its unique property of ice being less dense that water seems to of been essential to our existence, ie. the sea floor was not covered in a sheet of ice allowing life to get a foothold in the nutrient rich soil.

I would love to hear other thoughts on this topic, as far as i see it there are 2 possibilities. Either there is only one way life can exist, as DNA/RNA such as our own, in that possibility we should look for earth like planets or at least the presence of water. Or life can get started as long as there is the coming about of a self replicating molecule (what ever its composition) and natural selection can get started, driving evolution and producing complex life.

[canalon]

We have already thrown out one rule of biology with the absence of phosphorous in this microbe. Which of the other laws of biology can we get rid of.

Actually when looking at the paper in details, it seems that the claims might have been exaggerated and that basic test to confirm presence of arsenate in DNA (Mass spec of purified DNA or lipids or other molecules) have simply not been carried out. So life in absence of phosphorus is not yet proved and my first post fell for the hype.
Still I wish they carry those out and that it proves to be true.
And I think that your formulation of whatever you call the laws of biology is as much an hyperbole as what I made in response to your original post. There is no such things really, just generalized observations. Remember the black swans.

I would love to hear other thoughts on this topic, as far as i see it there are 2 possibilities. Either there is only one way life can exist, as DNA/RNA such as our own, in that possibility we should look for earth like planets or at least the presence of water. Or life can get started as long as there is the coming about of a self replicating molecule (what ever its composition) and natural selection can get started, driving evolution and producing complex life.

I would think that most serious biologist would go for the second option. The fact that water is abundant on earth make it a very good base for life on earth, but then again methane and ammonia lake are quite rare around this planet. In different set of conditions, I would think that life could exist, would probably evolve according to the same broad rules (accumulation and selection of mutations in a genetic code defined by available resources), but would be completely different. There is no reason that it should use the same molecules that we find on earth. Historical contingency is quite important to define what we see now.

[magicsiew]

I have read the original paper. The bacteria mentioned is from Halomonadaceae family in the Gammaproteobacteria.