What is the name of the long-term evolution experiment with E. coli that has been running since 1988?

The long-term evolution experiment with E. coli that began in 1988 is Lenski's experiment. Its formal name is the E. coli Long-Term Evolution Experiment, or LTEE, founded by evolutionary biologist Richard Lenski.

The study began on February 24, 1988, with 12 initially identical E. coli populations. Each population grows in a glucose-limited medium, and every day researchers transfer a small sample into fresh medium. This rapid life cycle allows scientists to observe tens of thousands of bacterial generations in a human lifetime.

One of the experiment's most famous discoveries occurred in population Ara-3, which evolved the ability to grow aerobically on citrate—an unusual trait for E. coli. Researchers used periodically frozen samples as a living “fossil record,” allowing them to replay earlier stages and compare ancestral bacteria with evolved descendants.

The experiment is often called simply “Lenski's experiment,” although LTEE is the more precise name. It is not the Miller-Urey experiment, which studied possible chemical origins of life, or Mendel's pea experiments, which helped establish classical genetics.