Archaea were separated from Eubacteria after discovery of their specifics in cell outer membrane that
usually not affected by common antibiotics. Phylogenetic analysis introduced by Karl Wöese supported this
separation. Presently, only two phyla Crenarchaeota and Euryarchaeota include the valid representatives. Another
three phyla that were proposed based on the sequence analysis of environmental samples, do not contain validly
published species, and for this reason they are not included in this review. The phylum Euryarchaeota currently
includes eight classes and ten orders, while the Crenarchaeota phylum contains the only class with five orders.
Members of the phyla Crenarchaeota have two or three family B and no family D DNA polymerases, but members
of the Euryarchaeota contain the only family B polymerases and the only family D polymerases, and it is still not
clear, which is the main functional enzyme in the replication process.
In this article, we are present an update and comparative analysis for this domain, discussing unique
features of this group and Evolution, estimating their physiology within the matrix of physic-chemical factors, and
outlining future perspectives in their study. Rules of the diagonal for the diagrams with all Archaea are presented