NASA discovers new lifeform with totally different DNA than anything else

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  • #26
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Yeah i wonder if it would be possible to produce a media that would have almost no trace of phosphate.
 
  • #28
mheslep
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Someone's got to do it:


Source: http://xkcd.com/829/
Arg. Beat me by 5 mins. I'll post the mouse-over text then.

According to a new paper published in the journal Science, reporters are unable to thrive in an arsenic-rich environment.
 
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  • #33
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Yeah ummmmmmmm the science out of nasa seems to get shakier every year. After a few days of reading on this im not sure theyve found anything but a bacteria that can tolerate lots of As crippleing its chemistry without dieing.
 
  • #34
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Here is another source that is skeptical
http://news.yahoo.com/s/yblog_thelookout/20101208/sc_yblog_thelookout/scientists-poking-holes-in-nasas-arsenic-eating-microbe-discovery [Broken]
 
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  • #35
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So did this turn out to be legit?
 
  • #36
Borek
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I guess the best way of describing the case is that they found something interesting, but it is probably not quite what they seem to be suggesting it is.
 
  • #37
Ygggdrasil
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So did this turn out to be legit?
It is still unclear. I'll probably take another few years for additional experiments to be done to figure out in detail which of the Science papers' claims are true and which are not (yes, science is a slow process, but it's slow because we want to get things right).

However, based on the data presented in the paper and what we know about the chemistry of arsenate esters, many are very skeptical of the claim that the bacterium's DNA has a different chemistry than normal DNA. There is no proof yet that the DNA is P-DNA but there is also no convincing proof that the DNA is As-DNA either.
 
  • #38
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Here is another source that is skeptical
http://news.yahoo.com/s/yblog_thelookout/20101208/sc_yblog_thelookout/scientists-poking-holes-in-nasas-arsenic-eating-microbe-discovery [Broken]
Here's the pertinent info from that ref I think:

"Redfield and other detractors point out that when NASA scientists removed the DNA from the bacteria for examination, they didn't take the steps necessary to wash away other types of molecules. That means, according to the critics, that the arsenic may have merely clung to the bacteria's DNA for a ride without becoming truly ingrained into it.

The report's detractors also note that the NASA scientists fed the bacteria salts that contained trace amounts of phosphate, so it's possible that the bacteria were able to survive on those tiny helpings of phosphate instead of the arsenic."
I mean I'm a little disappointed at the level of analytical chemistry going on here. Just seems like a simple matter to determine if arsenic is being incorporated into the biochemistry. I don't know, mass spec, atomic absorption maybe? Whatever, some good tools of analytical chemistry such as what's that reference for analytical pharmacology? I forgot but all the standard analytical methods. Surely there are reliable methods to determine if arsenic is presence in adenosine combinations such as adensone tri-arsenate (I think that's the right name) and in ribose-arsenate substitutions in the backbone of DNA.
 
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  • #39
Ygggdrasil
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Update: Rosie Redfield, a professor of zoology at the University of British Columbia and outspoken critic of the arsenic life paper, claims she has performed experiments to refute the main conclusion of Wolfe-Simon et al.'s paper. She has posted a non-peer-reviewed preprint of her manuscript on Arxiv.

In the manuscript, Redfield and co-workers detail experiments attempting to replicate growth of samples of the GFAJ-1 bacterium and, contrary to what was reported in the original paper, do not find that the bacterium displays arsenic-dependent growth. The authors also set out to test one of the boldest claims of the Wolfe-Simon paper: that the bacterium incorporates arsenic into its DNA. The authors employ a more rigorous DNA purification procedure than Wolfe-Simon et al. (they add a CsCl density centrifugation step), then digest the DNA for LC-MS analysis to look for evidence of arsenic. They find no evidence of arsenic incorporation into the DNA. Furthermore, their results suggest that the purification methods used in the Wolfe-Simon paper leave traces of free arsenic associated with the DNA, but this free arsenic is removed with more extensive washing and purification. This result suggest that the apparent incorporation of arsenic into DNA seen by Wolfe-Simon et al. was merely free arsenic that was incompletely purified from the DNA.

For more, you can read the following news articles from Science and Chemical and Engineering News or follow the story on Redfield's blog:
http://news.sciencemag.org/scienceinsider/2012/02/closely-watched-study-fails-to.html [Broken]
http://cen.acs.org/articles/90/web/2012/01/Arsenic-Based-Life-Aftermath.html
http://rrresearch.fieldofscience.com/search/label/#arseniclife
 
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  • #40
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Arsenic used as a replacement for phosphorus. Someone mentioned that phosphorus is more abundant than arsenic. However, this abundance of phosphorus on Earth is said to be unique to earth - http://www.reasons.org/where-did-earth-get-its-phosphorus.

Article does open up the possibility of life much different than on Earth, elsewhere. Not to suggest that because of this life does exist off planet, but if it does it can be more unusual than anticipated.
 
  • #41
Ryan_m_b
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Arsenic used as a replacement for phosphorus...

Article does open up the possibility of life much different than on Earth, elsewhere. Not to suggest that because of this life does exist off planet, but if it does it can be more unusual than anticipated.
Did you not read the post directly above yours? Here it is again (key points bolded):
Update: Rosie Redfield, a professor of zoology at the University of British Columbia and outspoken critic of the arsenic life paper, claims she has performed experiments to refute the main conclusion of Wolfe-Simon et al.'s paper. She has posted a non-peer-reviewed preprint of her manuscript on Arxiv.

In the manuscript, Redfield and co-workers detail experiments attempting to replicate growth of samples of the GFAJ-1 bacterium and, contrary to what was reported in the original paper, do not find that the bacterium displays arsenic-dependent growth. The authors also set out to test one of the boldest claims of the Wolfe-Simon paper: that the bacterium incorporates arsenic into its DNA. The authors employ a more rigorous DNA purification procedure than Wolfe-Simon et al. (they add a CsCl density centrifugation step), then digest the DNA for LC-MS analysis to look for evidence of arsenic. They find no evidence of arsenic incorporation into the DNA. Furthermore, their results suggest that the purification methods used in the Wolfe-Simon paper leave traces of free arsenic associated with the DNA, but this free arsenic is removed with more extensive washing and purification. This result suggest that the apparent incorporation of arsenic into DNA seen by Wolfe-Simon et al. was merely free arsenic that was incompletely purified from the DNA.

For more, you can read the following news articles from Science and Chemical and Engineering News or follow the story on Redfield's blog:
http://news.sciencemag.org/scienceinsider/2012/02/closely-watched-study-fails-to.html [Broken]
http://cen.acs.org/articles/90/web/2012/01/Arsenic-Based-Life-Aftermath.html
http://rrresearch.fieldofscience.com/search/label/#arseniclife
 
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