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posted 26. July 2002 12:15
The Three Domains of Life: A Challenge to the concept of the Universal Cellular Ancestor?
by Pattle.P.Pun, Stephen Schuldt, and Benjamin T. Pun
pattle.p.pun@wheaton.edu
ABSTRACT—With the discovery of the uniqueness of Archaebacteria in rRNA sequence and by comparative studies with well-characterized molecular systems, cell walls, lipid compositions and features of the transcriptional and translational machineries, the three domains of life, namely Archaea, Bacteria and Eukarya, has become the currently accepted paradigm in the field of molecular taxonomy. Sequence analyses based on functional proteins across the three domains also suggest each of the three domains as independent monophyletic lineage representing ribosomal, metabolic, biosynthetic proteins as well as the replicational, transcriptional and translational machineries. Current view suggests that the universal tree of life branched from the universal ancestor in separate lineages leading to Bacteria and Archaea, the latter then diverged into Eukarya. The search for the universal ancestor has led to postulating a universal communal gene pool (progenotes) in which lateral or horizontal gene transfer (HGT) played the most important role in diversification since the three domains of life are resistant to HGT after they have crystallized into cellular communities. This scenario challenges the concept of the Universal Cellular Ancestor and may be open to alternative views based on design.
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