Team gives ancient life another chance to evolve

Posted by Emma Woollacott

Researchers at the Georgia Institute of Technology are attempting to repeat the path of evolution by taking a gene from an ancient organism and watching it evolve.

In a process called paleo-experimental evolution, they've resurrected a 500-million-year-old gene from a bacterium and inserted it into modern-day E. coli bacteria - which has now been growing for more than 1,000 generations.

"This is as close as we can get to rewinding and replaying the molecular tape of life," says Betül Kaçar of Georgia Tech's NASA Center for Ribosomal Origins and Evolution.

"The ability to observe an ancient gene in a modern organism as it evolves within a modern cell allows us to see whether the evolutionary trajectory once taken will repeat itself or whether a life will adapt following a different path."

After placing the ancient gene in the right chromosomal order and position in place of the modern gene within E. coli, Kaçar produced eight identical bacterial strains and allowed 'ancient life' to re-evolve. The resulting bacteria, composed of both modern and ancient genes, survived - but grew only half as fast as its modern counterpart.

"The altered organism wasn't as healthy or fit as its modern-day version, at least initially," says associate professor of biology Eric Gaucher.

"This created a perfect scenario that would allow the altered organism to adapt and become more fit as it accumulated mutations with each passing day."

The growth rate did eventually increase - and, after the first 500 generations, the scientists sequenced the genomes of all eight lineages to determine how the bacteria adapted. Not only did the bateria's fitness levels increase almost to modern-day levels, but some of the altered lineages actually became healthier than their modern counterparts.

Interestingly, the bacteria appear to be evolving in a different manner to their ancient equivalents.

"We think that this process will allow us to address several longstanding questions in evolutionary and molecular biology," says Kaçar.

"Among them, we want to know if an organism's history limits its future and if evolution always leads to a single, defined point or whether evolution has multiple solutions to a given problem."