The taxonomy of life first set out by Linnaeus is familiar to anyone who has taken a basic interest in natural history. At the finest level life on Earth is divided into species that are grouped together in genera. Higher level groupings define families, orders, classes, phyla and then kingdoms. The original system of 1735 Linnaeus listed just two kingdoms for animals and plants. With the invention of the microscope it was realised that there are also bacteria that do not fit into either of these kingdoms. They are distinct because their DNA is not held in a nucleus. Over time the taxonomy system was refined until the 1969 classification of Whittaker with five kingdoms became accepted by biologists.
Initially classification was based on simple morphology. Later the chemical composition became more important. For example, fungi were placed in their own kingdom distinct from plants because their cell walls contain chitin instead of cellulose. Then in the 1970s a few scientists started to look at the RNA in the cells. One of them was Carl Woese who wanted to use the technique to help classify bacteria. When he was asked to apply his method to specialised bacteria that live in extreme conditions he found that the RNA was so different from other bacteria that it was wrong to put them in the same kingdom. At first he called them Archaebacteria, but then he decided that a more radical change to the top levels of taxonomy was needed. In the new system there would be three domains, bacteria, archaea and eukarya with the latter containing the more familiar kingdoms.
Carl Woese was born in 1928 in Syracuse and still holds a professorship at the University of Illinois. His scientific training was more in biophysics than traditional microbiology so to some extent he was an outsider in the field he was revolutionising. As we have seen before it is sometimes such people who come along with a different outlook on a subject, untethered by the ruling dogma. These are the people with a mind open enough to shift the paradigm, but they should expect a lot of resistance from the authorities on the subject. This was certainly the case for Woese.
Although Woese’s research was published in a top scientific journal, most biologists knew of it only through newspaper accounts. Unfamiliar with the new techniques used they immediately set about criticizing it. Nobel Laureat Salvador Luria openly derided any possibility of a three domain taxonomy believing it to be based on a classification game. Privately he contacted Ralph Wolfe, a colleague and supporter of Woese and told him ” you’re going to ruin your career. You’ve got to disassociate yourself from this nonsense!'” Others followed with a hostility that shocked Woese. Because they saw him as a physicist rather than a microbiologist they did not hesitate to call him a crank. They did not believe that the RNA studies he had carried out could be used to classify bacteria. They did not even bother to look at the data. Ernst Mayr, an icon of evolutionary biology could never accept the new conventions even when they became more widely accepted in 1990.
Woese was never allowed to defend his work on the conference circuits and his funding remained at a scathingly low level. Try as he might he could never get the money from the NFS Systematics panel increased even though with retrospect it was by far the most important research they ever funded.
Over time acceptance of his work grew and he started to collect some honours. Finally it was the possibility to sequence genomes that confirmed the verity of his work in 1996. Now it is widely understood and Woese has the recognition he always deserved. His work has been absorbed into the textbooks without any embarrassing mention of just how bitterly it was opposed for nearly twenty years. In some cases the name of Woese is conveniently left out when his work is described by those who attacked it for so long.
The taxonomy of the simplest lifeforms is tied into the study of early evolutionary biology and is a field that continues to develop. The groupings into domains and kingdoms will no doubt be modified again, but the work and techniques of Woese that recognised the differences of archae will remain as a revolutionary step that advanced microbiology to its modern form.