Within what had previously been called prokaryotes, there exist two distinct groups of organisms no more related to one another than they were to eukaryotes. Because of Woese’s work, it is now widely agreed that there are three primary divisions of living systems – the Eukarya, Bacteria, and Archaea, a classification scheme that Woese proposed in 1990.
The new group of organisms – the Archaea – was initially thought to exist only in extreme environments, niches devoid of oxygen and whose temperatures can be near or above the normal boiling point of water. Microbiologists later realized that Archaea are a large and diverse group of organisms that are widely distributed in nature and are common in much less extreme habitats, such as soils and oceans. As such, they are significant contributors to the global carbon and nitrogen cycles.
The method Woese used to identify this “third form of life,” which involved comparing the sequences of a particular molecule central to cellular function, called ribosomal RNA, has become the standard approach used to identify and classify all organisms. These techniques have also revolutionized ecology, because it is now possible to survey an ecosystem by collecting ribosomal DNA from the environment, thus sidestepping the often impossible task of culturing the organisms that are there. These microorganisms and the revolutionary methods that Woese introduced into science can offer insights into the nature and evolution of cells.
In 1996, Woese and colleagues (University of Illinois professor Gary Olsen and researchers from the Institute for Genomic Research) published in the journal Science the first complete genome structure of an archaeon, Methanococcus jannaschii. Based on this work, they concluded that the Archaea are more closely related to humans than to bacteria. “The Archaea are related to us, to the eukaryotes; they are descendants of the microorganisms that gave rise to the eukaryotic cell billions of years ago,” Woese said at the time.
“The Archaea are related to us, to the eukaryotes; they are descendants of the microorganisms that gave rise to the eukaryotic cell billions of years ago,” Woese said at the time.
Woese’s experimental discoveries were made in the context of his search for a deep understanding of the process of evolution. As early as the 1970’s Woese was thinking about what sort of theory of evolution one would need in the era before genes as we know them had emerged. At such a time, the standard population genetics theory of evolution would not be applicable. Woese articulated early clear proposals about the nature of what has come to be known as the last universal common ancestor, concluding for a variety of reasons that the universal ancestor was not a single organism, but rather groupings of loosely structured cells that existed together during a time when genetic mutation rates were high and the transfer of genes between cells occurred more frequently than in the present day. The most detailed version of these proposals was put forward on the basis of Woese’s work here at IGB (with University of Illinois professor Nigel Goldenfeld). These groups of primitive cells, called progenotes, evolved together and eventually formed the three ancestral lineages.
“Carl’s work, in my view, ranks along with the theory of superconductivity as the most important scientific work ever done on this campus – or indeed anywhere else,” says Dr. Nigel Goldenfeld, leader of the IGB Biocomplexity research theme and long-time colleague of Dr. Woese. “It remains one of the 20th century’s landmark achievements in biology, and a rock solid foundation for our growing understanding of the evolution of life.”
Woese passed away in December of 2012 at the age of 84.
Carl Woese was a professor of microbiology at the University of Illinois Urbana-Champaign and a faculty member of the Carl R. Woese Institute for Genomic Biology. He was awarded the John D. and Catherine T. MacArthur Foundation “genius” award in 1984, and the National Academy of Sciences elected him to membership in 1988. In 1992 the Dutch Royal Academy of Science gave him the highest honor bestowed upon any microbiologist, the Leeuwenhoek Medal, awarded only once every 10 years. He was given the National Medal of Science in 2000 “for his brilliant and original insights, through molecular studies of RNA sequences, to explore the history of life on Earth.” In 2003 the Royal Swedish Academy of Sciences awarded Woese the Crafoord Prize in Biosciences for his discovery of the third domain of life. The Crafoord award honors scientists whose work does not fall into any of the categories covered by Nobel Prizes. The Royal Society, the world’s oldest continuously active scientific organization, elected Woese as a foreign member in 2006. He held the Stanley O. Ikenberry Endowed Chair and served as Center for Advanced Study Professor of Microbiology.
