Scientists work ways to store digital information in DNA

Her computer, Karin Strauss says, contains her “digital attic” - a place where she stores that published math paper she wrote in high school, and computer science schoolwork from college. She’d like to preserve the stuff “as long as I live, at least,” says Strauss, 37. But computers must be replaced every few years, and each time she must copy the information over, “which is a little bit of a headache.” It would be much better, she says, if she could store it in DNA - the stuff our genes are made of.

Strauss, who works at Microsoft Research in Redmond, Washington, is working to make that sci-fi fantasy a reality. She and other scientists are not focused in finding ways to stow high school projects or snapshots or other things an average person might accumulate, at least for now. Rather, they aim to help companies and institutions archive huge amounts of data for decades or centuries, at a time when the world is generating digital data faster than it can store it.

To understand her quest, it helps to know how companies, governments and other institutions store data now: For longterm storage it’s typically disks or a specialized kind of tape, wound up in cartridges about three inches on a side and less than an inch thick. A single cartridge containing about half a mile of tape can hold the equivalent of about 46 million books of 200 pages apiece, and three times that much if the data lends itself to being compressed.

A tape cartridge can store data for about 30 years under ideal conditions, says Matt Starr, chief technology officer of Spectra Logic, which sells data-storage devices. But a more practical limit is 10 to 15 years, he says. It’s not that the data will disappear from the tape. A bigger problem is familiar to anybody who has come across an old eight-track tape or floppy disk and realized he no longer has a machine to play it. Technology moves on, and data can’t be retrieved if the means to read it is no longer available, Starr says.

So for that and other reasons, long-term archiving requires repeatedly copying the data to new technologies. Into this world comes the notion of DNA storage. DNA is by its essence an information-storing molecule; the genes we pass from generation to generation transmit the blueprints for creating the human body. That information is stored in strings of what’s often called the four-letter DNA code. That really refers to sequences of four building blocks - abbreviated as A, C, T and G - found in the DNA molecule. Specific sequences give the body directions for creating particular proteins. Digital devices, on the other hand, store information in a two-letter code that produces strings of ones and zeroes. A capital “A,” for example, is 01000001. Converting digital information to DNA involves translating between the two codes. In one lab, for example, a capital A can become ATATG. The idea is once that transformation is made, strings of DNA can be custom-made to carry the new code, and hence the information that code contains.

One selling point is durability. Scientists can recover and read DNA sequences from fossils of Neanderthals and even older life forms. So as a storage medium, “it could last thousands and thousands of years,” says Luis Ceze of the University of Washington, who works with Microsoft on DNA data storage. Advocates also stress that DNA crams information into very little space. Almost every cell of your body carries about six feet of it; that adds up to billions of miles in a single person. In terms of information storage, that compactness could mean storing all the publicly accessible data on the internet in a space the size of a shoebox, Ceze says.

In fact, all the digital information in the world might be stored in a load of whitish, powdery DNA that fits in space the size of a large van, says Nick Goldman of the European Bioinformatics Institute in Hinxton, England. What’s more, advocates say, DNA storage would avoid the problem of having to repeatedly copy stored information into new formats as the technology for reading it becomes outmoded.

“There’s always going to be someone in the business of making a DNA reader because of the health care applications,” Goldman says. “It’s always something we’re going to want to do quickly and inexpensively.” Getting the information into DNA takes some doing. Once scientists have converted the digital code into the 4-letter DNA code, they have to custom-make DNA. For some recent research Strauss and Ceze worked on, that involved creating about 10 million short strings of DNA. — AP