Monday, January 13, 2014

On the unpredictability of evolution and potentiation in Lenski's long-term evolution experiment

Richard Lenski's long-term evolution experiment (LTEE) has yielded a number of interesting results over the past two decades. Back in 1988, he set up twelve flasks of E. coli B growing in minimal medium. The cultures were diluted 1/100 every day. There were 6.64 generations per day or almost 2,500 per year. By now, the cultures have evolved for 60,000 generations.

All twelve cultures are under strong selection for rapid growth and all twelve cultures have evolved. One, and only one, of the cultures evolved to utilize citrate as a carbon source (normal E. coli cultures cannot use citrate but it's in the medium as a chelating agent). You can read about the mutations that gave rise to this phenotype in: Lenski's long-term evolution experiment: the evolution of bacteria that can use citrate as a carbon source.

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