Re: Life's range = 0-50C


<Jeremy.Winfield@xxxxxxxxx> wrote in message news:f693d1$2819$1@xxxxxxxxxxxxxxxxxxxxxx

You're correct in showing criticism for the hyperthermophilic origin
of the LCA. Truth is that the first dividing cell may have been a
mesophile.

Er. The LCA and the first dividing cell could have been a billion years
apart.

However, given how deeply rooted thermophiles are in the
tree of life, I feel its better evidence than the contrary. It is
also good to note that many enzymes using metal cofactors are also
highly divergent and well rooted. Since there is a high concentration
of metal ions around deep sea volcanic vents, this seems to point us
toward that location for the origin of life. To make a terrible
metaphor, I can just see in my minds eye a sea of thermodynamic and
reduction/oxidation energy around deep sea vents as being favorable
for the first enzymes to ride the free energy roller coaster.

I have not read deeply into spontaneous polymerization, but it is
possible under some laboratory conditions, and there are references in
the composomes paper that I sited earlier. It's curious seeing a
trade off here- RNA's h-bonds are too unstable at high temperatures,
yet any kind of genetic templating cannot occur without RNA (or
possibly not?), and proteins are indeed more stable, and yet cannot
systematically self clone themselves amino acid per amino acid. How
did these two interact in the LCA?

Why should they have interacted any differently than they do today?
Ie. no spontaneous polymerization of amino acids. And no self-replication
of peptides. Only polymerization driven by expenditure of phosphate
bond energy and guided by nucleic acid genes. And I suspect that
this was true all the way back to the first dividing cell. Because
spontaneous polymerization is uncontrolled polymerization and can't
create anything useful with a defined sequence.

[snip]


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