Biography
The development of technology for molecular sequence analysis in the 1970's revolutionized the way we can evaluate evolutionary relationships between different organisms. Gene sequence comparisons provide some objective measure of the evolutionary distances by which modern organisms are separated; the more different the gene sequences, the more different the organisms. The information can be used to infer how gene sequences must have evolved over time, yielding a sort of family tree for genes. Carl Woese, at the University of Illinois, generated, and subsequently compared, molecular sequences (known as rRNA) that contain the code for part of the cell's ribosome---a complex structure that makes proteins, and thus is present in all cells. His studies established the outlines of the universal tree of life and showed that known biological diversity falls into three groups, or so-called phylogenetic domains: archaea, bacteria and eucarya (eucaryotes).
The identification of organisms by sequences - analogous to barcodes - also meant that molecular technology could be used to fish genes out of the environment for sequence analysis and comparative studies, independently of the traditional requirement for laboratory culture. For the first time it was possible to explore meaningfully the makeup of the natural microbial world. Studies of rRNA and other genes obtained from many environments have dramatically expanded our knowledge of the diversity and distribution of environmental microbes. The results significantly flesh-out the molecular tree of life - but also tell us that we are merely scratching the surface of an enormous extent of biological diversity.
