Jeffrey Barrick and his colleagues find that bacteria that are slow to adapt end up "winning" the evolutionary race against bacteria that adapt fast. Image from "The Æsop for Children," by Æsop. Illustrated by Milo Winter.
AUSTIN, Texas–When it comes to survival of the fittest, it’s sometimes better to be an adaptable tortoise than a fitness-oriented hare, researchers say.
In this week’s Science magazine, Jeffrey Barrick, assistant professor of chemistry and biochemistry at The University of Texas at Austin, Richard Lenski, the Hannah Distinguished Professor of Microbiology and Molecular Genetics at Michigan State University, and colleagues show that more adaptable bacteria oriented toward long-term improvement prevailed over competitors that held a short-term advantage.
The result that the less-fit organisms overtook their in-shape counterparts surprised the researchers at first. But it turns out to work something like a game of chess.
“In games it makes sense to sacrifice some pieces for an eventual winning move,” explains Lenski, co-principal investigator of BEACON, the National Science Foundation-funded Science and Technology Center at Michigan State University. “The eventual winners were able to overcome their short-term disadvantage over the course of several evolutionary moves by producing more beneficial mutations.”
Lenski and his team recently revived a frozen population of E. coli and compared the fitness and ultimate fates of four clones representing two genetically distinct lineages. One lineage eventually took over the population even though it had significantly lower competitive fitness than the other lineage that later went extinct.
By replaying evolution over and over with the clones, the researchers showed that the eventual winners likely prevailed because they had greater potential for further adaptation.
“In essence, the eventual loser lineage seems to have made a mutational move that gave it a short-term fitness advantage but closed off certain routes for later improvement,” Lenski explains. “And the dead-end strategy allowed the eventual winners to catch up and eventually surpass the eventual losers.”
So, yes, sometimes the tortoise really does beat the hare.
Barrick and Lenski’s collaborators include co-author Robert Woods, an MSU graduate who worked in Lenski’s laboratory and is now a physician scientist at the University of Michigan; Tim Cooper from the University of Houston; MSU undergraduate student Mark Kauth; and University of Houston student Utpala Shrestha.
For more information contact: Layne Cameron, Michigan State University, 517-353-8819; Jeffrey Barrick, The University of Texas at Austin, 512-471-3247; Lee Clippard, The University of Texas at Austin, 512-232-0675
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