"The coupling between genomic and adaptive evolution is complex and can be counterintuitive," Lenski concluded. "The genome was evolving along at a surprisingly constant rate, even as the adaptation of the bacteria slowed down a lot. But then suddenly the mutation rate jumped way up, and a new dynamic relationship was established."
A mutation involved in DNA metabolism arose around generation 26,000, causing the mutation rate everywhere else in the genome to increase dramatically. The number of mutations jumped to 653 by generation 40,000, but researchers surmise that most of the late-evolving mutations were not helpful to the bacteria.
Gene mutations involved in human DNA replication are involved in some cancers. Many of the patterns observed in the experiment also occur in certain microbial infections, "and cancer progression is a fundamentally similar evolutionary process," observed collaborator Jeffrey Barrick. "So what we learn here can help us better understand the course of these diseases."
Barrick, a postdoctoral researcher in MSU's Department of Microbiology and Molecular Genetics, developed computational tools to discover and validate often complex mutations. "We know an astounding amount about the details of evolution in these little Erlenmeyer flasks," he said.
The Nature paper involved collaboration with scientists from South Korea as well as France and MSU. The research, said genomics team leader Jihyun Kim of the Korea Research Institute of Bioscience and Biotechnology, "is not only useful in understanding the tempo and mode of evolution, but can serve as a nice framework for practical applications in biotechnology, such as improving the performance or productivity of an industrial strain."
Thousands of generations later, the MSU experiment continues to evolve. "Like a lot of science, our study answers some questions but raises many others," Lenski said.
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| Contact: Mark Fellows mark.fellows@ur.msu.edu 517-884-0166 Michigan State University Source:Eurekalert |