A subkingdom of the Prokaryotae (See Classification). The archaebacteria are placed in a group separate from the rest of the bacteria (the eubacteria) on the basis of a variety of biochemical characteristics (distinctive compounds in their cell walls and membranes, differences in rare bases found in their tRNAs, and distinctive structures of RNA polymerase subunits). The archaebacteria are thought to have been dominant organisms in the primeval biosphere, since its atmosphere was rich in carbon dioxide and included hydrogen but virtually no oxygen. The magnitude of the molecular differences between these microorganisms and other bacteria supports the proposal that the taxonomic name be changed from Archaebacteria to simply Archaea. See Chronology, 1977, Woese and Fox; extremophiles, flagellin, halophiles, methanogens, sulfur-dependent thermophiles, TATA box-binding protein (TBP).
Subjects: Genetics and Genomics.