Early work on the genetic code Woese turned his attention to the
genetic code while setting up his lab at
General Electric's
Knolls Laboratory in the fall of 1960.
Discovery of the third domain For much of the 20th century, prokaryotes were regarded as a single group of organisms and classified based on their
biochemistry,
morphology and
metabolism. In a highly influential 1962 paper,
Roger Stanier and
C. B. van Niel first established the division of cellular organization into
prokaryotes and
eukaryotes, defining prokaryotes as those organisms lacking a
cell nucleus. Adapted from
Édouard Chatton's generalization, Stanier and Van Niel's concept was quickly accepted as the most important distinction among organisms; yet they were nevertheless skeptical of microbiologists' attempts to construct a natural
phylogenetic classification of bacteria. However, it became generally assumed that all life shared a common prokaryotic (implied by the
Greek root πρό (pro-), before, in front of) ancestor. 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. Notably, Woese's elucidation of the
tree of life shows the 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
biogeochemical cycles and to the continued function of the biosphere, Woese's research on how microbes evolve and their different types has provided data used by
ecologists and
conservationists. It was a major contribution to the theory of
evolution and to our knowledge of the history of life. Woese wrote, "My evolutionary concerns center on the bacteria and the archaea, whose evolutions cover most of the planet's 4.5-billion-year history. Using ribosomal RNA sequence as an evolutionary measure, my laboratory has reconstructed the phylogeny of both groups, and thereby provided a phylogenetically valid system of classification for prokaryotes. The discovery of the archaea was in fact a product of these studies". First described by Woese and Fox in a 1977 paper and explored further with microbiologist
Jane Gibson in a 1980 paper, these organisms, or
progenotes, were imagined as protocells with very low complexity due to their error-prone translation apparatus ("noisy genetic transmission channel"), which produced high mutation rates that limited the specificity of cellular interaction and the size of the genome. This early translation apparatus would have produced a group of structurally similar, functionally equivalent proteins, rather than a single protein. The transition to modern cells (the "
Darwinian Threshold") occurred when organisms evolved translation mechanisms with modern levels of fidelity: improved performance allowed cellular organization to reach a level of complexity and connectedness that made genes from other organisms much less able to displace an individual's own genes. He worked on detailed analyses of the phylogenies of the aminoacyl-tRNA synthetases and on the effect of horizontal gene transfer on the distribution of those key enzymes among organisms. The goal of the research was to explain how the primary cell types (the archaeal, eubacterial, and eukaryotic) evolved from an ancestral state in the
RNA world. == Perspectives on biology ==