The Tangled Tree: A Radical New History of Life

by David Quammen

Then, in 1978, a new paper of high interest to both men appeared in a relatively obscure European journal. This paper, from a French team in Strasbourg, offered something never yet seen: the complete sequence of bases (not just a sampling of fragments) for Woese’s molecule of record, 16S rRNA, from a single bacterium. The bacterium was that familiar bug E. coli. The method of sequencing was essentially Fred Sanger’s, modified by use of a new ingredient: extract of cobra venom, to help cut the molecule. The information value of the full sequence, to researchers such as Woese and Doolittle, was huge. Until this point, they had been comparing fragments—those short blurts of letters—without knowing how the fragments might fit together. The French team, with their cobra venom, had revealed the fit. But that European journal was slow in reaching the University of Illinois. Woese, having caught wind of the paper, was impatient. So he called Doolittle in Halifax, where the journal had arrived, and asked a favor: “Would you read me the sequence?” Doolittle obliged. Sitting in his office, with the October issue of the journal, he recited all 1,542 letters to Woese by telephone. He found that reading them in triplets gave a natural rhythm, making it easier to avoid omissions or duplications. That is, he said: “AAA, UUG, AAG, AGU, UUG, AUC,” and so on. He said, “AUG, GCU, CAG, AUU, GAA, CGU,” and so on. He said, “UGG, GAU, UAG.” UAG is a stop codon, a signal to terminate, when it appe...