Synthetic biologists have been able to encode a kind of rewritable memory directly into DNA, after seeking ways to use biological data-storage systems effectively. This would be the fundamental function of any kind of digital circuitry that synthetic biologists hope to integrate into living cells.
The researchers, led by Drew Endy of Stanford University in California, published their findings yesterday in the journal Proceedings of the National Academy of Sciences. There have been rewritable biological memory circuits in the past, but in the previous ones, once the memory had been set into the circuit, it could be erased and encoded with a new memory state. Endy and his group tried to create rewritable memory systems by splicing genetic elements from a bacteriophage into the DNA of the bacterium Escherichia coli.
The system is made up of a stretch of DNA that’s flanked by sites that will signal to enzymes made by the bacteriophage, giving them instructions to cut out the DNA and paste it back into the chromosome in reverse orientation. Endy has shown that this can be done repeatedly, up to 16 times. The advantage of this system compared to ones using transcription factors is that it has a digital analogue, with forward and reverse orientations of DNA acting like the ‘0’ and ‘1’ in the binary system.
The group had chosen a specific bacteriophage for the work, but it didn’t work as planned. In turn, Jerome Bonnet spent three years tweaking the system in order to make it work and troubleshooting various aspects of the design. He created 750 different versions to find one that could work.