Ancient gene planted in modern bug to track evolution

Friday July 13, 2012 08:12:16 AM, IANS

Washington: US researchers have resurrected a 500-million-year-old gene from bacteria and inserted it into modern-day E. coli bug to see whether the evolutionary trajectory once taken will repeat itself or whether a life will adapt following a different path.

They relied on a process called paleo-experimental evolution. The bug has now been growing for more than 1,000 generations, giving the scientists a front seat to observe evolution in the real world, just as Jurassic Park did with the reel version.

"This is as close as we can get to rewinding and replaying the molecular tape of life," said scientist Betul Kacar, NASA astrobiology postdoctoral fellow in Georgia Institute of Technology NASA Centre 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," said Kacar.

In 2008, Kacar's postdoctoral advisor, Eric Gaucher, associate professor of biology, successfully determined the ancient genetic sequence of Elongation Factor-Tu (EF-Tu), an essential protein in E.coli, according to a Georgia statement.

EFs are one of the most abundant proteins in bacteria, found in all known cellular life and required for bacteria to survive. That vital role made it a perfect protein for the scientists to answer questions about evolution.

After placing the ancient gene in the correct chromosomal order and position in place of the modern gene within E. coli, an extremely difficult task, Kacar produced eight identical bacterial strains and allowed "ancient life" to re-evolve.

"The altered organism wasn't as healthy or fit as its modern-day version, at least initially," said Gaucher, "and 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 eventually increased 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 fitness levels increase to nearly modern-day levels, but also some of the altered lineages actually became healthier than their modern counterpart.

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

These results were presented at the recent NASA International Astrobiology Science Conference.

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