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The two-domain system is a biological classification by which all organisms in the tree of life are classified into two domains, Bacteria and Archaea. [ 1 ] [ 2 ] [ 3 ] It emerged from development of knowledge of archaea diversity and challenges the widely accepted three-domain system that classifies life into Bacteria, Archaea, and Eukarya . [ 4 ]
Two kingdoms, Archaebacteria (archaea) and Eubacteria (for bacteria) were established. [22] Based on further studies, Woese, Otto Kandler and Mark Wheelis introduced the concept of "domain" in 1990 as the highest level of biological classification, and proposed the three-domain system consisting of Eucarya, Bacteria and Archaea. [23]
The word archaea comes from the Ancient Greek ἀρχαῖα, meaning "ancient things", [16] as the first representatives of the domain Archaea were methanogens and it was assumed that their metabolism reflected Earth's primitive atmosphere and the organisms' antiquity, but as new habitats were studied, more organisms were discovered.
In 1990 Carl Woese et al. introduced the three-domain system. [35] [36] The prokaryotes were split into two domains, the archaea and the bacteria, while the eukaryotes become a domain in their own right. The key difference from earlier classifications is the splitting of archaea from bacteria.
The two-empire system would later be expanded to the three-domain system of Archaea, Bacteria, ... the diagram below is an 'organization chart', ...
The two-empire system or superdomain system, proposed by Mayr (1998), with top-level groupings of Prokaryota (or Monera) and Eukaryota. [11] [12] The eocyte hypothesis, proposed by Lake et al. (1984), [13] which posits two domains, Bacteria and Archaea, with Eukaryota included as a subordinate clade branching from Archaea. [14] [13] [15]
Metagenomic analyses recover a two-domain system with the domains Archaea and Bacteria; in this view of the tree of life, Eukaryotes are derived from Archaea. [ 58 ] [ 59 ] [ 60 ] With the later gene pool of LUCA's descendants, sharing a common framework of the AT/GC rule and the standard twenty amino acids, horizontal gene transfer would have ...
Schematic diagram of the Thermococcus gammatolerans cell pictured above. Pyrococcus furiosus. In taxonomy, the Thermococci are a class of microbes within the Euryarchaeota. [1] They live in extremely hot environments, such as hydrothermal vents, and they have optimal growth temperatures above 80 °C.