Re: Life's range = 0-50C
- From: "Perplexed in Peoria" <jimmenegay@xxxxxxxxxxxxx>
- Date: Fri, 29 Jun 2007 13:33:41 -0400 (EDT)
<Jeremy.Winfield@xxxxxxxxx> wrote in message news:f5u870$2euo$1@xxxxxxxxxxxxxxxxxxxxxx
I feel it my duty as a biologist who has worked with hyperthermophilic
organisms to correct you on multiple points.
Thx for the informed response. But you should be aware that Tom, to
whom you responded, is not a scientist and has no ambition to become a
scientist. He is an amateur with a fascination for the problem of the
origin of life. Like myself (though I like to tell myself that I know
a bit more about chemical thermodynamics than Tom.)
You are about 71C off on your upper temperature limit of. The limit
for reproducible life, that is, a bug that divides and grows is
currently at 121C (http://www.sciencemag.org/cgi/content/citation/
301/5635/934), and biologists continue to probe this upper limit,
believing it can be expanded. Allow me to reemphasize, life not only
grows at this temperature, it *thrives.* Some Thermotoga microbes are
impossible to keep in culture because they lyse when brought to
normal mesophilic temperatures.
There is also strong evidence, as shown between the free energy of
binding between alpha and beta subunits of tryptophan synthase in
Thermus thermophilus (http://www.jbc.org/cgi/content/abstract/
M210893200v1), that the enthalpy of salt bridges helps to drive
folding rather than the entropy of hydrophobic collapse. This would
explain the bias of salt bridges in thermophilic proteins. The
knowledge base in which you are stating your broad hypothesis also
appears to lack a thorough understanding of thermodynamics and protein
folding.
Interesting. Is there also a structural feature common to thermophilic
structural RNAs? I've heard that they are more GC rich in their stems,
but I've also seen this disputed.
It is also a general consensus amongst biologists that the last common
ancestor was most likely a thermophile, since it is so deeply rooted
in the tree of life. Read the following for more detail: [URL snipped]
It is a fairly widespread belief, but I wouldn't call it a consensus.
And hyperthermophily (or not) of the LCA really tells us little about
the conditions for the origin of life.
It is also a general consensus that life evolved from spontaneous
events of polymerization from early protein-metal precursors around
volcanic vents. I would google "composomes" to find out more on this
([snip big URL]).
Interesting. I had never heard of this hypothesis. At least not the
part about spontaneous polymerization. Are the ideas of the Segre group
considered 'consensus' now. Personally, I like the slogan of a
'lipid world', but I'm pretty skeptical regarding their specifics.
Especially their lingering commitment to a heterotrophic origin.
[Snip invective against Tom. No doubt he deserves this abuse, but the
more common practice here is to either ignore him or humor him.]
.
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