WIKIMEDIA; BRIAN BAER, NEERJA HAJELAFor more than 30 years, Richard Lenski and his team at Michigan State University have been propagating the same 12 cultures of E. coli, transferring the cells to new media every day. The experiment has allowed the researchers to see how the bacteria evolve, and in 2008 they published results suggesting that some of the cultures had begun to use citrate as a carbon source. But it took 15 years for such citrate-eating microbes to arise—a delay Lenski and colleagues attributed to “historical contingency,” or the slow accumulation of mutations required for the adaptation.
This month (February 1), however, researchers publishing in the Journal of Bacteriology suggested that perhaps the exciting development was simply a result of the experimental conditions, and showed that making certain tweaks to the culture environment could elicit such citrate-eating mutants much sooner than in Lenski’s long-running study. “We’re showing that there’s a simple genetic explanation for the acquisition of citrate mutants in the long-term evolution experiments—that there’s no historical contingency required,” the University of Idaho’s Scott Minnich, a fellow of the Seattle-based nonprofit Discovery Institute, told The Scientist.
“What the new experiment has told us is [that] actually these phenotypes can evolve much more readily than we initially thought,” said Rees Kassen, who was not involved in the research. “To me [this] suggests that ...
