Researchers at Harvard Medical School have come up with a find-and-replace tool for editing the genetic code of living bacteria. The technique offers a more powerful way to manipulate living organisms, and could eventually be used to make industrial microbes that are safer, more robust, and produce new kinds of drugs and chemicals.
Most of the genes that make up an organism’s genetic code are essentially design plans for making proteins. Each gene consists of a long strand of molecules, called nucleotides. Three such nucleotides—a group known as a codon—tell a cell which amino acids it should use while building a protein.
Cells can use 22 naturally occuring amino acids as building blocks to make proteins, but chemists have synthesized over a hundred so-called “unnatural amino acids” in the lab using the tools of chemistry, not biology. Naturally occuring organisms can’t make or build with these chemicals. Organisms that could build proteins using these amino acids would open up new possibilities, particularly in drug development. But normal cells lack the necessary genetic code to work with these unnatural amino acids.
A team at Harvard, led by George Church, has developed a tool for editing genes that could change this. To make microbes capable of building proteins that incorporate unnatural amino acids, researchers need to be able to both edit all of certain codons in the genome, and to manipulate the cell machinery that reads those codons. The new tool lets them do the first part.
Church says he hopes to achieve three goals with the approach. First, he wants to build bacteria that can produce new drugs and other chemicals. Second, he wants to genetically engineer bacteria that cannot live outside the lab because they need unnatural amino acids to survive—a feat that could prevent the environmental damage that might result from such bacteria being let loose in the world. And third, he wants to make bacteria that are immune to viruses, since viruses can cause problems in industrial production. “The way to achieve all these things is to change the [meaning of the] genetic code of your favorite organism,” says Church.