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NASA Earth Science

NASA Confirms Discovery of Organism With Phosphorus-Free DNA 380

Posted by timothy
from the well-it's-not-that-shaggy dept.
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."
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NASA Confirms Discovery of Organism With Phosphorus-Free DNA

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  • by yincrash (854885) on Thursday December 02, 2010 @04:09PM (#34422076)
    To be very clear, Felisa (the primary paper author) stated during the Q&A that all they know for sure is that there is not enough phosphorus in the bacteria for it's biochemical processes and the only reasonable conclusion is that arsenic is taking it's place. Not enough analysis to know percentages of what is using what.
  • by MichaelSmith (789609) on Thursday December 02, 2010 @04:26PM (#34422340) Homepage Journal

    In fact arsenic is toxic to you precisely because it takes the place of phosphorus so easily, without doing all of the jobs. Except for this little guy, who manages to work around the differences and survive nearly phosphorus-free.

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

  • by mcgrew (92797) * on Thursday December 02, 2010 @04:49PM (#34422640) Homepage Journal

    This link [purdue.edu] may help. If not (it is, after all, a link to the chemistry department of a university), this [wikipedia.org], this [wikipedia.org], or this [wikipedia.org] may.

    And yes, since it has to do with DNA it is indeed porn on acid. Or maybe acid on porn.

  • by gilleain (1310105) on Thursday December 02, 2010 @04:56PM (#34422728)

    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

    Hmmm. Maybe it methylates the DNA more? Or the histones are different. I guess - as you say - more repair enzymes is quite likely, since that just requires some promoter mutations.

    The interesting question for me is whether any of the mechanisms are different for this organisms enzymes. For the last few months I've been sitting on the next desk to the maintainer of a database of biochemical mechanisms (MACiE - hi gemma, assuming you read slashdot, and happy birthday...) so maybe that's why it occurs to me. Many enzymes use ATP/NAD/other phosphate cofactors to make stuff, so if AsO4 has a slightly different chemistry, I wonder if different sidechains are used. Or, as I say, some completely different mechanisms (or pathways?).

  • by Defenestrar (1773808) on Thursday December 02, 2010 @04:56PM (#34422730)
    Sounds good except for the fact that you're forgetting that arsenate is more reactive than phosphate which means the arsenate based backbone of DNA should be constantly getting ripped to shreds. Either this bacteria has found a way to protect the backbone or it has a hyper effective repair mechanism. Either would be very worth learning about. (Immortality anyone)?
  • by patjhal (1423249) on Thursday December 02, 2010 @05:20PM (#34423098)
    Yes. This is pretty significant. I wonder if there are any viruses that can effect them. Read about the Hershey–Chase experiment if you want to see how significant this is https://secure.wikimedia.org/wikipedia/en/wiki/Hershey%E2%80%93Chase_experiment [wikimedia.org]
  • by Defenestrar (1773808) on Thursday December 02, 2010 @05:35PM (#34423366)

    Thanks for filling in the blanks. There's some things that I deal with so often that I forget I can sound a little weird when I get excited about science and open my mouth - phosphate is one of them.

    But yeah - the short story is that phosphate (and arsenate) have three spots to kick hydrogen on or off with - and the number of hydrogens that hang out on a phosphate ion is very much related to the pH.

    The long story (for anyone who cares) is that each of those hydrogens has a different equilibrium constant (pKa) at which it will pop off. H3PO4 is phosphoric acid but if you increase the amount of OH- in solution (or reduce the amount of H+) the first of those hydrogens will hook up with the OH- to make water which leaves H2PO4-. So the next hydrogen to take a hike will leave the phosphate at HPO4- - which means it's harder to leave and has a different pH (which is a fancy way of talking about the levels of H+ and OH- in water) it will hit equilibrium with. So on and so forth for each of the four phosphate species (0, -1, -2, -3 charge).

    The really long version throws out concentration of the different species of phosphate and talks about activities, taking into account that the activity coefficient is affected by the square of the ion's charge... [We interrupt this chemistry lesson for the sake of sanity]

    Strange - I forgot what I was talking about - but back to your question: yeah - DNA is both sex and acid

  • Holy crap! (Score:4, Interesting)

    by DG (989) on Thursday December 02, 2010 @07:22PM (#34425008) Homepage Journal

    What if this microbe isn't "new" - what if it is old?

    As in - what if life on Terra initially evolved based around an arsenic atom, and then later evolved to use the much better and more stable phosphorus?

    DG

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