“Programmable data storage within the DNA of living cells would seem an incredibly powerful tool for studying cancer, aging, organismal development and even the natural environment,” said Stanford assistant professor Drew Endy. Researchers could count how many times a cell divides, for instance, and that might someday give scientists the ability to turn off cells before they turn cancerous.
In the computer world, their work would form the basis of what is known as non-volatile memory — data storage that can retain information without consuming power. In biotechnology, it is known as “recombinase-mediated DNA inversion,” after the enzymatic processes used to cut, flip and recombine DNA within the cell.
The team calls its device a “recombinase addressable data” module, or RAD for short. They used RAD to modify a particular section of DNA with microbes that determines how the one-celled organisms will fluoresce under ultraviolet light. The microbes glow red or green depending upon the orientation of the section of DNA. Using RAD, the engineers can flip the section back and forth at will.
To make their system work, the team had to control the precise dynamics of two opposing proteins, integrase and excisionase, within the microbes. “Previous work had shown how to flip the genetic sequence irreversibly — in one direction through the expression of a single enzyme,” said Stanford postdoctoral scholar Jerome Bonnet, “but we needed to reliably flip the sequence back and forth, over and over, in order to create a fully reusable binary data register.”