Ever since Charles Darwin traveled to the Galapagos Islands in the 19th century, “use it or lose it” has been the adopted theory when studying the evolution of organisms.
Scientists at MSU have recently learned that successful adaptation to a specific environment is all about trade-offs.
In a paper published in the Oct. 12 edition of the British science journal “Nature,” university researchers work to untangle one of the big questions in evolution: Do populations become more specialized and give up functions because it’s efficient or because unused functions allow genetic mutations to accumulate?
“What leads to a reduction in function is a big question, and we’ve never been able to identify which mechanism is more important,” said Vaughn Cooper, a former MSU postdoctoral researcher who’s now an assistant professor of biology at the University of Michigan.
“The two mechanisms are always coinciding in evolution and are hard to disentangle.”
Cooper, a co-author of the “Nature” paper, said he studied a series of 12 strains of E. coli bacteria confined to growing on glucose. The bacteria had been kept for more than 10 years, accumulating more than 20,000 generations.
And Cooper said most of that bacteria lost the ability to grow on other sugars after being confined to the glucose. The research indicated the E. coli grew stronger by what is called antagonistic pleiotropy - or dumping unnecessary attributes and focusing on what works best.
The conclusions reached can be seen working in organisms living in caves, such as bats. They’ve evolved blind, and Cooper said studying bacteria in a laboratory can be translated into other areas.
“You can’t observe a cave environment over hundreds of years,” he said. “But you need to be cautious about extrapolating from bacteria to cave organisms.”
Richard Lenski, a Hannah professor of microbial ecology who co-authored the “Nature” paper, said there’s no other comparable experiment on the dynamics of evolution done on such a scale.
“We’ve been running this particular experiment for over a decade, and that’s given us more than 20,000 generations of bacteria to study,” he said. “Some of our previous work with these bacteria demonstrated so-called ‘punctuated’ dynamics, where there are periods of rapid change alternating with relative constancy.”
Lenski said the next step for researchers is finding and manipulating some of the genes that mutated while the bacteria adapted to glucose.
“If we’re successful, I think we will have one of the most detailed pictures of evolution ever,” he said. “One that spans from the genomic level up to the macro-level changes we’ve observed in cell morphology, physiology and ecology.”
