As opposed to any macro manifestation, when the cellular form is deemed central to all eukaryotic multicellular organisms, the unicellular state through which all multicellular eukaryotes must recapitulate can be reappraised.
Some of the NCLDV encode ATP-dependent ligases that, among cellular life forms, are ubiquitous and essential for replication in archaea and eukaryotes, but are only sporadically found in bacteria where they seem to contribute to distinct forms of DNA repair [ 14- 16].
In this case, the expression profile patterns for the cellular and extracellular forms are the same (upregulation).
The nature of the primary divide in prokaryotes – and actually among all cellular life forms is clear, and it is between archaea and bacteria.
We maintain, however, that the purported formal demonstration of the Universal Common Ancestry of all known cellular life forms is illusory.
Firstly, the conservation of the hallmark proteins in extremely diverse classes of viruses with widely different replication/expression strategies (Table 3) but not in cellular life forms is hardly compatible with the rapid divergence interpretation.
My general view which I see no reason whatsoever to change is expressed in the following quote from my review of a previous publication by the same authors: "The nature of the primary divide in prokaryotes - and actually among all cellular life forms is clear, and it is between archaea and bacteria.
The simplest explanation of the fact that the hallmark proteins involved in viral replication and virion formation are present in a broad variety of viruses but not in any cellular life forms is that the latter never had these genes in the first place.
Nature is thrifty, and the genetic codes behind many cellular processes in simpler life forms "are very much mirrored in humans," said Professor Hartman.
With improved detection methods eukaryotic features are increasingly being identified in prokaryotes and it is becoming clear that the transition between these two major cellular forms may have been more gradual that previously suspected (Table 1).
