to Benzer's research, it was not known whether the gene was a linear structure, or if it had a branching pattern. E. coli was one of the first organisms to have its genome sequenced; the complete genome of E. coli K-12 was published by Science in 1997. Lenski's long-term evolution experiment The long-term evolution experiments using E. coli, begun by Richard Lenski in 1988, have allowed direct observation of major evolutionary shifts in the laboratory. In this experiment, one population of E. coli unexpectedly evolved the ability to aerobically metabolize citrate. This capacity is extremely rare in E. coli. As the inability to grow aerobically is normally used as a diagnostic criterion with which to differentiate E. coli from other, closely related bacteria such as Salmonella, this innovation may mark a speciation event observed in the lab. References Escherichia coli Gram-negative bacteria