Biologists are Engineering Kill Switches for GM Microbes

DNATo keep old trains running, operators had to keep a firm grip on a dead man’s switch. If the operator became incapacitated or, well, dead, his hand would loosen, the brakes would engage, and the train wouldn’t turn into a runaway—no active intervention required. That was 20th century engineering. In the 21st century, where scientists are as likely to engineer microbes as locomotives, “Deadman” is a kill switch created by MIT biologists to prevent engineered microbes from running out of control in the wild. Deadman and another microbial kill switch called Passcode are the newest of the increasingly sophisticated ways biologists hope to control microbes they’re building to cure diseases or clean up oil and toxic spills. Without those controls, the bugs will never leave the lab. “The biggest enemy we have is uncertainty,” says Karmella Haynes, a synthetic biologist at Arizona State University. “We don’t have a practical way to prove tomorrow that GMOs are absolutely dangerous or absolutely safe. The appropriate response to uncertainty is, let’s arm ourselves with an engineering solution.”

The simplest kill switches simply deleted a gene that made some molecule critical to the life of the organism. Without scientists feeding that molecule to the microbe, it died. The risk was that microbes in the wild might find an unexpected source for it. As paradoxical as it might sound, synthetic biology companies have good reason to want to kill their products under the right circumstances: protect the public from possible dangers and protect it from competitors. That’s two for the price of one technology, even better than the dead man’s switch of trains.

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