Figure 2.

Genome trees of archaea. (A) Gene content tree. (B) Tree based on conserved gene pairs. Solid lines show terminal branches and internal branches with >90% bootstrap support, and dotted lines show internal branches with <90% support. The three methanogen species are highlighted by red, green, and blue. The bacterial species included as an outgroup are shown in magenta. Species abbreviations: Euryarchaeota: A. fulgidus (Arcfu), M. thermoautotrophicum (Metth), M. jannaschii (Metja), M. kandleri (Metka), Pyrococcus horikoshii (Pyrho), Pyrococcus abyssi (Pyrab), Thermoplasma volcanium (Thevo), Thermoplasma acidophilum (Theac), Halobacterium sp. (Halsp); Crenarchaeota: Aeropyrum pernix (Aper), Sulfolobus solfataricus (Sulso); bacteria: Thermotoga maritima (Thema), Deinococcus radiodurans (Deira), Escherichia coli (Escco).