Evolution ‘replay’ shows that unknown catastrophe wiped out bacterial strain
NEERJA HAJELA AND BRIAN BAER/MICHIGAN STATE UNIVERSITY
Sometimes extinction is just a fluke, a long-term experiment in evolution has shown.
Scientists captured an extinction in a bottle during a 27-year-long study in evolutionary biologist Richard Lenski’s lab at Michigan State University in East Lansing. Researchers there have been growing 12 flasks containing Escherichia coli bacteria. Those bacteria have been evolving for more than 60,000 generations.
In one of those flasks, called Ara-3, some of the bacteria evolved the ability to eat a chemical called citrate (SN: 1/31/09, p. 26; SN: 10/20/12, p. 8). For more than 10,000 generations, the citrate eaters, called Cit-plus, lived side-by-side with Cit-minus E. coli that couldn’t digest the chemical. But then sometime between generation 43,500 and 44,000, the Cit-minus