In two parallel projects, researchers have created new genomes inside the bacterium E. coli in ways that test the limits of genetic reprogramming and open new possibilities for increasing flexibility, productivity and safety in biotechnology.
In one project, researchers created a novel genomethe first-ever entirely genomically recoded organismby replacing all 321 instances of a specific "genetic three-letter word," called a codon, throughout the organism's entire genome with a word of supposedly identical meaning. The researchers then reintroduced a reprogramed version of the original word (with a new meaning, a new amino acid) into the bacteria, expanding the bacterium's vocabulary and allowing it to produce proteins that do not normally occur in nature.
In the second project, the researchers removed every occurrence of 13 different codons across 42 separate E. coli genes, using a different organism for each gene, and replaced them with other codons of the same function. When they were done, 24 percent of the DNA across the 42 targeted genes had been changed, yet the proteins the genes produced remained identical to those produced by the original genes.
"The first project is saying that we can take one codon, completely remove it from the genome, then successfully reassign its function," said Marc Lajoie, a Harvard Medical School graduate student in the lab of George Church. "For the second project we asked, 'OK, we've changed this one codon, how many others can we change?'"
Of the 13 codons chosen for the project, all could be changed.
"That leaves open the possibility that we could potentially replace any or all of those 13 codons throughout the entire genome," Lajoie said.
The results of these two projects appear today in Science. The work was led by Church, Robert Winthrop Professor of Genetics at Harvard Medical School and founding core faculty member at the Wyss Institute for Bi
|Contact: David Cameron|
Harvard Medical School