Work and Discoveries
Having defined Archaea as a new domain, Woese redrew the taxonomic tree. His three-domain system, based on genetic relationships rather than obvious morphologic similarities, divided life into 23 main divisions, incorporated within three domains: Bacteria, Archaea, and Eucarya. Archaea are neither bacteria nor eukaryotes. They can be viewed as prokaryotes that are not bacteria.
Notably, Woese's elucidation of the tree of life shows the overwhelming diversity of microbial lineages; single-celled organisms represent the vast majority of the biosphere's genetic, metabolic, and ecologic niche diversity. As microbes are crucial for many biogeochemical cycles and to the continued function of the biosphere, Woese's efforts to clarify the evolution and diversity of microbes provided an invaluable service to ecologists and conservationists.
Acceptance of the validity of Woese's classification was a slow process. Famous figures, including Salvador Luria and Ernst Mayr, objected to his division of the prokaryotes. Not all criticism of him was restricted to the scientific level. Not without reason has Woese been dubbed "Microbiology's Scarred Revolutionary" by the journal Science. The growing amount of supporting data led the scientific community to accept the Archaea by the mid-1980s. Today, few scientists cling to the idea of a unified Prokarya.
Woese also speculated about an era in which considerable horizontal gene transfer occurred between organisms. Species formed when organisms stopped treating genes from other organisms with equal importance to their own genes. Horizontal gene transfer during this era was responsible for the fast early evolution of complex biological structures.
Woese's work is also significant in terms of its implications for the search for life on other planets. Prior to Woese, Archaea were thought to be extreme organisms that evolved from the organisms more familiar to us. Many scientists now believe they are ancient, and may have robust evolutionary connections to the first organisms on Earth. Organisms similar to those archaea that exist in extreme environments may have developed on other planets, some of which harbor conditions conducive to extremophile life.
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