rRNA unlocks the domains Emile Zuckerkandl (1922-2013); Austria & USA. Molecular biology and molecular clock Linus Carl Pauling (1901-1994) USA Founder of fields like quantum chemistry and molecular biology Suggested that a tree of life might be generated by comparing sequences of biopolymers like RNA Zuckerkandl and Pauling
What’s the ‘S’? • Svedberg units: a measure of how quickly particles sediment in an ultracentrifuge • Larger the particle, the greater its S value • Smaller subunit of a ribosome sinks slower than the larger subunit
The system we propose here will repair the damage that has been the unavoidable consequence of constructing taxonomic systems in ignorance of the likely course of microbial evolution, and on the basis of flawed premises (that life is dichotomously organized; that negative characteristics can define meaningful taxonomies). - Carl R. Woese, Otto Kandler, and Mark L. Wheelis. 1990. Towards a natural system of organisms: Proposal for the domains Archaea, Bacteria, and Eucarya. Proceedings of the National Academy of Sciences. USA. 87: 4576-4579.
Eubacteria >9 Kingdoms Same type of ribosomes Polysaccharide of outer wall made of Murein Most groups involved in global nutrient cycling Many of economic importance Disease Other functions (e.g. antibiotic producers)
Three Domains Modified from McInerney et al. 2015 Eukaryotes Early Eocyte Ring of Life Argued that the domain concept was indefensible because eukaryotes are not monophyletic unless we consider all of life