The Oldest Ancestor Genome?

The origins of life represent a fascinating problem that has been
addressed using different approaches and a wide variety of technologies. A
theoretical approach consists of inferring a possible oldest ancestor
genome from a well-defined comparison of current ones. Mushegian and
Koonin did
this in 1996, creating a hypothetical Minimal Gene Set (MGS). In this new
paper from PLoS Computational Biology, Davide Chiarugi, Pierpaolo Degano,
and Roberto Marangoni, from the universities of Siena and Pisa, prove that
this MGS would not have been able support life.



One of the difficulties of such a hypothetical genome is validating it as
a functional biological system. The direct solution of synthesizing such a
genome in a laboratory is often extremely difficult, due to the great
complexity of a biological cell. In this paper, the authors present an
approach
for evaluating the chances a hypothetical organism has to be really
viable, relying on computer simulations.



The authors assumed the two conditions of reaching equilibrium and
producing biomass to be essential for an organism to live. The previous
MGS-prokaryote clearly does not express these qualities, but by adding new
genes and changing some of the previous ones, the authors managed to
produce a genome which adhered to their criteria of life - Virtual Cell
(ViCe). This is some 60 genes smaller than the MGS, and demonstrates
qualities similar to those seen in live bacteria, therefore indicating,
that this, in fact, could be the oldest ancestor genome.




A previous version of this article appeared as an Early Online Release on
July 26, 2007 (doi:10.1371/journal.pcbi.0030174.eor).
Please click here.



CITATION: Chiarugi D, Degano P, Marangoni R (2007) A computational
approach to the functional screening of genomes. PLoS Comput Biol 3(9):
e174.
doi:10.1371/journal.pcbi.0030174




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