Harvard scientists led by Jeff Nivala and Seth Shipman have discovered a remarkable way to store lines of code in living bacteria, which can then be passed down to the next generation as genetic information. Based on a new study, bacteria colonies when fed by a series of human-written data can transform tiny cells into living hard drives. According to Shipman, genotyping the bacteria could easily read the data from these living memory sticks. This type of experiment allows the transfer of 100 bytes of data, almost ten times more than possible with artificial DNA. Previously, the scientists had attempted this experiment but with synthetic DNA. The technique used by the scientists practically tricked the bacteria into copying actual computer code into their DNA without compromising their own cellular activities. “Rather than synthesizing DNA and cutting it into a living cell, we wanted to know if we could use nature’s own methods to write directly onto the genome of a bacterial cell, so it gets copied and pasted into every subsequent generation,” says Shipman. “But working within a living cell is an entirely different story and challenge.” “We write the information directly into the genome. While the overall amount of DNA data we have currently stored within a genome is relatively small compared to the completely synthetic DNA data storage systems, we think genome-based information storage has many potential advantages,” Nivala told Gizmodo. He says that these advantages could include higher fidelity and the capability to directly interface with biology. For example, a bacterium could be taught to identify, provide information, and even kill other microorganisms in its midst, or provide a record of genetic expression. “Depending on how you calculate it, we stored between about 30 to 100 bytes of information,” said Nivala. “Which is quite high compared to the previous record set within a living cell, which was ~11 bits.” Going forward, the kind of bacteria one uses is important. The researchers used E. coli for this particular experiment that clocks in a fairly respectable storage of 100 bytes. However, certain bacteria, such as Sulfolobus tokodaii may be capable of storing thousands of bytes. To protect certain bacteria from viral infection, the scientists used the bacteria’s built-in immune system called CRISPR or Cas system. When the bacteria are attacked by viruses, they physically cut out a segment of the invaders’ DNA and paste it into a specific region of their own genome. This way, if that same virus attacks again, the bacteria can identify it and respond accordingly. Thus, the cell passes this information over to its progeny of the bacteria, transferring the viral immunity to next generations. The bacteria research team discovered that by introducing a segment of genetic data that looks like viral DNA into a colony of bacteria that have the CRISPR/Cas system, the bacteria would devour it and include it in their genetic code. Therefore, the scientists spread the loose segments of DNA into the E.coli bacterial colony that had the CRISPR. They gulped it all up essentially becoming tiny, living hard drives. The segments used were arbitrary strings of A, T, C, G nucleotides with pieces of viral DNA at the end. Shipman introduced one segment of information at a time and allowed the bacteria do the rest, storing away information like fastidious librarians. Conveniently enough, the bacteria store new immune system entries in sequence, with earlier viral DNA recorded before that of more recent infections. “That’s quite important,” Shipman says. “If the new information was just stored randomly, that wouldn’t be nearly as informative. You’d have to have tags on each piece of information to know when it was introduced into the cell. Here it’s ordered sequentially, like the way you write down the words in a sentence.” The findings have been published in Science.
