arsenic based life form

[David Morris]

First, I'm quoting & linking to the blog post of Dr. Athena Andreas on
the Huffington Post:
http://www.huffingtonpost.com/athena-andreadis-phd/arsenic-and-odd-lace_b_791454.html

She says:
The tables in the Science paper are eloquent on how reluctant even
hardy extremophiles are to use As instead of P. Under normal growth
conditions, the As:P ratio in their biomass was 1:500. When P was
rigorously excluded and As had been raised to three times the level in
lake Mono, the As:P ratio remained at a measly 7:1. Furthermore, upon
fractionation As segregated almost entirely into the organic phase.
Very little was in the aqueous phase that contains the nucleic acids.
This means that under extreme pressure the bacteria will harbor
intracellular As, but they will do their utmost to exclude it from the
vital chains of the genetic material.

But she later updates:
Addendum: Upon re-reading, the paper has evidence that the DNA of the
final isolate contains 11% of the total arsenic by incorporation of
radioactivity and mass spectrometry comparison studies. The crucial
questions are: exactly where is it located, how much substitution has
occurred and how does it affect the layers of DNA function
(un/folding, replication, transcription, translation)? Definitive
answers will require at least direct sequencing and/or
crystallographic data. The leading author, Dr. Felisa Wolfe-Simon,
said that this is fertile ground for thirty years of future work --
and she's right.

So maybe she was being premature?


On Fri, Dec 3, 2010 at 3:17 PM,  <malignd at aol.com> wrote:
> <<Nor do they tell us anything about terrestrial evolution, because they showcase a context-driven re-adaptation, not a de novo alternative biochemistry. >>
>
> David, could you go a little further?  What I've read suggested that it might be either a re-adaptation or a de novo alternate.  Too early to say, is what I gathered.  If not, why not?