The Peon Posted December 3, 2010 Share Posted December 3, 2010 http://www.escapistmagazine.com/news/view/105811-NASA-Discovers-New-Life http://www.nasa.gov/topics/universe/features/astrobiology_toxic_chemical.html Link to comment Share on other sites More sharing options...
Red Hypergiant Posted December 4, 2010 Share Posted December 4, 2010 Yes, this is an excellent discovery, and I think that it was mentioned on Through the Wormhole once. It's almost certain that we will find other life in the solar system. Link to comment Share on other sites More sharing options...
divagreen Posted December 13, 2010 Share Posted December 13, 2010 (edited) I found it amazing... Mono Lake, CaliforniaImage: Image © 2010 Henry Bortman The finding, published today (December 2) on the Science Express Web site, throws into doubt the long-held belief that phosphorus is absolutely essential to life, and broadens the range of environments in which scientists might expect to find extraterrestrial organisms. "This is a surprise," said biochemist Barry Rosen of Florida International University, who was not involved in the research. "Not just for bacteria but for life in general, arsenic is one of the few elements that is considered to be only toxic and has no role in metabolism." It's "pretty damn surprising," agreed ecologist James Elser of the Arizona State University, who also did not participate in the study. "I've spent my career studying phosphorus limitation, and how organisms use phosphorus, and how nucleic acids always have phosphorus in them, and now there's this exception. That's what's really weird." Arsenic falls directly below phosphorus on the period table, and thus has many similar chemical properties. In contrast to relatively stable phosphorus-based molecules, however, arsenic compounds are extremely unstable. While phosphorus compounds take years, decades, or even millennia to break down, the rate of hydrolysis of arsenic compounds is usually measured in seconds or minutes. In fact, its similarity to phosphorus and its instability partly explains why arsenic is so toxic. The body may not be able to distinguish between phosphate -- the most common form of phosphorus in organisms -- and its arsenic equivalent, arsenate. As a result, scientists suspect that arsenate can be incorporated into molecules and pathways that normally use phosphate, causing downstream processes to fail if the arsenate molecules are quick to break down or otherwise don't work properly. But at least one organism seems to have tackled this problem. Sampling the sediment of Mono Lake in California, a salt lake with high dissolved arsenic concentrations, NASA astrobiologist Felisa Wolfe-Simon of the US Geological Survey and her colleagues identified a bacterium that can grow when cultured with arsenic, but only trace amounts of phosphorus. Under conditions of high arsenic, the bacteria didn't grow as well as when phosphorus was abundantly available, but they grew significantly more than when neither arsenic nor phosphorus was provided. "That says, to me, that they really are using the arsenic," Rosen said. Read more: Arsenic supports life? - The Scientist - Magazine of the Life Sciences http://www.the-scientist.com/news/displ ... z170W6QMUC The component that makes up DNA has been changed? I find that startling, especially since the science behind it presents it on a molecular and metabolic level. Edited December 13, 2010 by divagreen Link to comment Share on other sites More sharing options...
CharonY Posted December 13, 2010 Share Posted December 13, 2010 (edited) I think, i commented on ti elsewhere already, but it has to be noted that the bacterium does not have an arsenic base. It only has been shown that it is able to incorporate a lot of arsenic, including levels in which P has presumably been exchanged by As (this has mostly been demonstrated indirectly). Moreover, the data is not perfectly clear on whether the cells really utilized As for growth or e.g. managed to do it in presence of the limited P still present (or released from the increased rate of dying cells). At least that was my impression after a quick read a while ago. I still have not gotten to re-read it in more detail, but this paper has been criticized heavily elsewhere. I still consider it a very interesting finding, however, it is not a demonstration of an organism with an As base. Edited December 13, 2010 by CharonY Link to comment Share on other sites More sharing options...
Incendia Posted December 13, 2010 Share Posted December 13, 2010 People are over-reacting...the scientists aren't even sure how Arsenic is incorporated into it... Link to comment Share on other sites More sharing options...
jimmydasaint Posted December 26, 2010 Share Posted December 26, 2010 I think that I would like more reproducibility in other laboratories, and more critical evaluation before I find it particularly awesome. Charon Y has highlighted my main concerns already. Link to comment Share on other sites More sharing options...
CharonY Posted December 28, 2010 Share Posted December 28, 2010 (edited) People are over-reacting...the scientists aren't even sure how Arsenic is incorporated into it... Well that is not a particular mystery for the most part. The basic asumption is that due to the equilibrium shift P would subsequently be replaced by As. Normally, this would result in inactive biomolecules and eventually death of the organism. Edited December 28, 2010 by CharonY Link to comment Share on other sites More sharing options...
Horza2002 Posted January 12, 2011 Share Posted January 12, 2011 (edited) From what I've read and using my chemistry knowledge, what they mean is that they have found bacteria that can survive very high levels of As (higher than would be fatal for humans). However, given that any As bond formed in a biolical system would hydrolyse very rapidly (they are rather weak), its unlikely that the bacteria would have any of them in te first place...but isolating them would be nearly impossible as well. Edited January 12, 2011 by Horza2002 Link to comment Share on other sites More sharing options...
mississippichem Posted January 12, 2011 Share Posted January 12, 2011 From what I've read and using my chemistry knowledge, what they mean is that they have found bacteria that can survive very high levels of As (higher than would be fatal for humans). However, given that any As bond formed in a biolical system would hydrolyse very rapidly (they are rather weak), its unlikely that the bacteria would have any of them in te first place...but isolating them would be nearly impossible as well. Yeah, I think I said this in the other thread about this. Show me the [ce]^{75}As [/ce] of the DNA oligomer then I'll believe it. Until then, mass spec doesn't mean much. Great, there's arsenic somewhere in your sample... As you stated, on stability grounds, I doubt they will ever find arsenate subbed out for phosphate between the ribose sugars. Link to comment Share on other sites More sharing options...
Horza2002 Posted January 12, 2011 Share Posted January 12, 2011 I don't think you will ever have As subsituted for P in a biological system. Im pretty sure that As is so toxic because it takes the place of P in compounds like ATP where it then rapidly hydrolyses degrading the molecule making it useless for the organism. So for an organism to have As bonds then it'l never survive. Link to comment Share on other sites More sharing options...
CharonY Posted January 12, 2011 Share Posted January 12, 2011 I would have just used soft ionization of the DNA and see whether there is a mass increase from P to As. If there was a significant exchange at least some should be detectable. Considering the relative ease of that experiment, I am quite confused why they did not try that. Link to comment Share on other sites More sharing options...
Horza2002 Posted January 12, 2011 Share Posted January 12, 2011 CharonY, how is that experiment performed? Do you need to have isolated the DNA first before you can analyse it. If so, I think that'l be the problem because the As bond wouldn't survive being isolated. Link to comment Share on other sites More sharing options...
mississippichem Posted January 13, 2011 Share Posted January 13, 2011 I would have just used soft ionization of the DNA and see whether there is a mass increase from P to As. If there was a significant exchange at least some should be detectable. Considering the relative ease of that experiment, I am quite confused why they did not try that. You mean like electro-spray mass spec? Link to comment Share on other sites More sharing options...
CharonY Posted January 13, 2011 Share Posted January 13, 2011 (edited) Probably I would use the MALDI. The likelihood of fragmentation is probably a bit lower. Also I suspect quite a bit of salt contamination.It could be a bit tricky to deal with adduct formation. Edited January 13, 2011 by CharonY Link to comment Share on other sites More sharing options...
Horza2002 Posted January 14, 2011 Share Posted January 14, 2011 For MALDI though, you would need to isolate the DNA and then suspend it in the appropriate matrix...and as I said in the previous posts, any As bond in the system would be extremely unlikely to survive the isolation process Link to comment Share on other sites More sharing options...
CharonY Posted January 14, 2011 Share Posted January 14, 2011 (edited) It may depend on the isolation and (if required) separation method, I would say. However if it would not even survive that one would require serious explanations how it is going to maintain integrity within a cell (where it is processed heavily).However, if it we end up with single nucleotides, it does make things easier to interpret, as we have defined m/zs to search for. Edited January 14, 2011 by CharonY Link to comment Share on other sites More sharing options...
Horza2002 Posted January 14, 2011 Share Posted January 14, 2011 That is my point...if the As bond couldn't survive being isolated, how could it ever be found in the cell. But I guess we will have to wait and see if they release any further data released by them providing some evidence of the As incoporation into some structure.... Link to comment Share on other sites More sharing options...
mississippichem Posted January 14, 2011 Share Posted January 14, 2011 Does anyone know if the arsenic analogue of tri-phosphate [tri-arsenate] has every been observed, even en vitro [perhaps in dichloromethane]? A cell running on ATA instead of ATP would be a more noteworthy find. Seems doubtful that could occur though do to the As-O bond's tending to be hydrolyzed as has been mentioned many times before. Link to comment Share on other sites More sharing options...
Horza2002 Posted January 14, 2011 Share Posted January 14, 2011 http://www.johndcook.com/blog/2010/12/02/nasa-arsensic-based-file/ This page seems to outline more clearly what they are implying...although they still give no evidence of isolating any compounds, nucleotides or anything that contain arsenic. Ive just done a search using Web of Knowledge for "adenosine tri arsenate" and there doesn't seem to be any papers based on them....that doesn't mean its not though. Link to comment Share on other sites More sharing options...
hypervalent_iodine Posted January 16, 2011 Share Posted January 16, 2011 (edited) I read the actual paper that this was presented in some time ago. They were of the belief that they would only ever incorporate As if P was in very low abundance, which makes sense. It's more of an evolutionary adaptation to survive in certain extremes. It has obvious implications in terms of metabolism, and from memory when the As was incorporated the colonies didn't proliferate so well, they just maintained themselves. If you look up "A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus" you should find the paper published in Science. Edited January 16, 2011 by hypervalent_iodine 1 Link to comment Share on other sites More sharing options...
thewanderingjack Posted January 21, 2011 Share Posted January 21, 2011 Thank you very much hypervalent_iodine, found the paper right off, and it answered some questions (raised a lot more). As you suggest, this seems more in line with evolutionary adaptation, not much different from a lot of research that's gone into developing organisms that feed on pollutants, except that this doesn't seem as effective so far. Anyone have info on any (even vaguely) similar studies? Link to comment Share on other sites More sharing options...
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