According to current estimates, the amount of data produced by humans and machines is rising at an exponential rate, with the digital universe doubling in size every two years. Very likely, the magnetic and optical data-storage systems at our disposal won’t be able to archive this fast-growing volume of digital 1s and 0s anymore at some point. Plus, they cannot safely store data for more than a century without degrading.
One solution to this pending global data-storage problem could be the development of DNA — life’s very own information-storage system — into a digital data storage medium.
Researchers already are encoding complex information consisting of digital code into DNA’s four-letter code comprised of its A, T, G, and C nucleotide bases. DNA is an ideal storage medium because it is stable over hundreds or thousands of years, has an extraordinary information density, and its information can be efficiently read (decoded) again with advanced sequencing techniques that are continuously getting less expensive.
What lags behind is the ability to write (encode) information into DNA. The programmed synthesis of synthetic DNA sequences still is mostly performed with a decades-old chemical procedure, known as the “phosphoramidite method,” that takes many steps that, although being able to be multiplexed, can only generate DNA sequences with up to around 200 nucleotides in length and makes occasional errors. It also produces environmentally toxic by-products that are not compatible with a “clean data storage technology.”
Previously, George Church’s team at Harvard’s Wyss Institute for Biologically Inspired Engineering and Harvard Medical School (HMS) has developed the first DNA storage approach that uses a DNA-synthesizing biological enzyme known as Terminal deoxynucleotidyl Transferase (TdT), which, in principle, can synthesize much longer DNA sequences with fewer errors. Now, the researchers have applied photolithographic techniques from the computer chip industry to enzymatic DNA synthesis, and thus developed a new method to multiplex TdT’s superior DNA writing ability. In their study published in Nature Communications, they demonstrated the parallel synthesis of 12 DNA strands with varying sequences on a 1.2 square millimeter array surface.
“We have championed and intensively pursued the use of DNA as a data-archiving medium accessed infrequently, yet with very high capacity and stability. Breakthroughs by us and others have enabled an exponential rise in the amount of digital data encrypted in DNA,” said corresponding author Church. “This study and other advances in enzymatic DNA synthesis will push the envelope of DNA writing much further and faster than chemical approaches.”
Church is a core faculty member at the Wyss Institute and lead of its Synthetic Biology Focus Area with DNA data storage as one of its technology development areas. He also is professor of genetics at HMS and Professor of Health Sciences and Technology at Harvard and MIT.
While the group’s first strategy using the TdT enzyme as an effective tool for DNA synthesis and digital data storage controlled TdT’s enzyme activity with a second enzyme, they show in their new study that TdT can be controlled by the high-energy photons that UV-light is composed of. A high level of control is essential as the TdT enzyme needs to be instructed to add only one single or a short block made of one of the four A, T, G, C nucleotide bases to the growing DNA strand with high precision at each cycle of the DNA synthesis process.