Georgia Institute of Technology researchers have been dabbling with a process known as paleo-experimental evolution in order to resurrect a 500 million-year-old bacterial gene, according to a recent press release on the Georgia Tech website. By injecting the 500 million-year-old gene into modern day Escherichia coli (E. coli), scientists have been able to observe 1,000 generations of evolution in action.
“This is as close as we can get to rewinding and replaying the molecular tape of life,” said Betül Kaçar, NASA astrobiological postdoctoral fellow in Georgia Tech’s NASA Center for Ribosomal Origins and Evolution. Mr. Kaçar says, “The ability to oberve 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.“
According to the press release, “In 2008, Kaçar’s postdoctoral advisor, Associate Professor of Biology Eric Gaucher, successfully determined the ancient genetic sequence of Elongation Factor-Tu (EF-Tu), an essential protein in E.coli.” These EFs are found in all known cellular life but are particularly prevalent in bacteria, which require the gene to survive.
Mr. Kaçar first delicately replaced the modern gene with the ancient one, producing eight replicas of ancient bacterial strains in order to observe the re-evolution of life. The bacteria survived the transplant, but according to the press release, “grew about two times slower than its counterparts.” Mr. Gaucher was quoted as saying, “The altered organism wasn’t as healthy or fit as its modern-day version, at least initially, but 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.”
After the first 500 generations, scientists sequenced each strain’s genome in order to examine how the bacteria had evolved. The article states, “Not only did the fitness levels increase to modern-day levels, but also some of the altered lineages actually became healthier than their modern counterpart.” Rather than mutating itself, the ancient EF-Tu interacted with modern proteins in such a way that rapidly improved the bacteria’s fitness, giving it what the article calls a new evolutionary trajectory to adapt.
Results of the study were presented at the NASA Astrobiology Science Conference. Scientists at Georgia Tech will continue to observe generations of bacteria to explore where the new evolutionary path will take them.
Mr. Kaçar says, “We think that this process will allow us to address several longstanding questions in evolutionary and molecular biology. 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.”