Long-Term Evolution Experiment with E. coli

In 1988, Richard Lenski started the LTEE, or long-term evolution experiment, in order to observe and analyze the process of evolution in action. Twelve populations were started from the same ancestral strain of Escherichia coli B, and they have been propagated in a glucose-limited minimal medium at 37 C ever since. Every day, 1% of each population is transferred into fresh medium, and this process has continued ever since. Every 500 generations, samples are frozen at -80 C for later analyses. This experiment has provided insights into the process of adaptation by natural selection, the repeatability of evolution, the dynamics of genome evolution, the origin of new functions, the evolution of mutation rates, and more.