Scientists have resurrected a 500-million-year-old bacterial gene and inserted it into modern E. coli bacteria. The new chimera bacteria have grown for more than 1,000 generations and have given scientists opportunity to observe a replay of evolution.
According to a Georgia Tech news release, the researchers determined the sequence of the 500 million years old form of a gene called Elongation Factor-Tu (EF-Tu). EF-Tu is found in all cellular life and cells need it to survive, so finding its ancient version provides opportunity for insight into the course of genetic evolution. Betul Kacar, an astrobiology postdoctoral fellow at Georgia Tech's NASA Center for Ribosomal Origins and Evolution, determined the location for the gene in E. coli chromosomes and inserted the "ancient" gene into modern E. coli . Then she produced eight identical strains of E. coli carrying the "ancient" gene.
The new "chimeric" versions of E. coli at first grew about twice as slowly as its modern counterpart.
According to the Georgia Tech researchers, the bacteria were cultured in the laboratory and have now lived through 1,000 generations. The Daily Mail reports that the scientists are hoping to find out whether the "ancient" bacteria will evolve the same way they did the "first time round" or whether they will evolve into a different organism.
According to Betul Kacar, a NASA astrobiology postdoctoral fellow at Georgia Tech, "This is as close as we can get to rewinding and replaying the molecular tape of life."
Kacar and her colleagues allowed the bacteria to grow for 500 generations. They observed that the growth rates increased gradually after the first 500 generations until some of them were even better off than the modern, unaltered strains.
According to Kacar: "The altered organism wasn’t as healthy or fit as its modern-day version, at least initially, 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." She added: "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."
The scientists sequenced the genomes of all eight lineages to determine how the bacteria have adapted. They found that the ancient EF-Tu did not accumulate mutations. Instead, the modern proteins that were interacting with the ancient gene inside the bacteria mutated. The mutations were responsible for the increased fitness of the chimera strains. That is, the ancient genes did not mutate to become more similar to the modern form but found a novel evolutionary pathway.
The researchers concluded that the observation was important because it answers the question whether the evolutionary process always yields the same outcome or whether it can lead to different outcomes or different solutions to the same problem. According to the researchers, the result so far suggests that nature can be creative, coming up with different solutions to the same problem.
According to Popsci.com, results were presented at the recent NASA International Astrobiology Science Conference. The scientists said they are still studying the new bacterial generations to determine whether the proteins will follow the historical path and become more similar to the modern form or whether a new or novel evolutionary path will be selected.
Kacar said: "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."