Scientists in Britain on Wednesday announced a breakthrough in the quest to turn DNA into a revolutionary form of data storage.
A speck of man-made DNA can hold mountains of data that can be
freeze-dried, shipped and stored, potentially for thousands of years,
they said.
The contents are "read" by sequencing the DNA - as is
routinely done today, in genetic fingerprinting and so on - and
turning it back into computer code.
"We already know that DNA is a robust way to store information
because we can extract it from bones of woolly mammoths, which date back
tens of thousands of years, and make sense of it," said Nick Goldman of
the European Bioinformatics Institute (EBI) in Cambridge.
"It's also incredibly small, dense and does not need any power for storage, so shipping and keeping it is easy."
DNA is the famous double helix of compounds - a long, coiled
molecular "ladder" comprising four chemical rungs, adenine, cytosine,
guanine and thymine, which team up in pairs. C teams up with G, and T
teams up with A.
The letter sequence comprises the genome, or the chemical
blueprint for making and sustaining life. Human DNA has more than three
billion letters, coiled into packages of 24 chromosomes.
The project entails taking data in the form of zeros and 1s in
computing's binary code, and transcribing it into "Base-3″ code, which
uses zeros, 1s and 2s.
The data is transcribed for a second time into DNA code, which
is based on the A, C, G and T. A block of five letters is used for a
single binary digit.
The letters are then turned into molecules, using lab-dish chemicals.
The work does not entail using any living DNA, nor does it seek
to create any life form and in fact the man-made code would be quite
useless in anything biological, the researchers said.
"We have absolutely no intention of messing with life," said Goldman.
Only short strings of DNA can be made, which means the message
has to be chopped up into small sections of 117 letters, each attached
to a tiny address tag, rather like packet-switching in Internet data,
which enables data to be reassembled.
To prove their concept, the team encoded an MP3 recording of
Martin Luther King's "I Have A Dream" speech; a digital photo of their
lab; a PDF of the landmark study in 1953 that described the structure of
DNA; a file of all of Shakespeare's sonnets; and a document that
describes the data storage technique.
"We downloaded the files from the Web and used them to
synthesise hundreds of thousands of pieces of DNA. The result looks like
a tiny piece of dust," said Emily Leproust of Agilent, a US biotech
company that took the digital data and used it to synthesise molecules
of DNA in the lab.
Agilent then mailed the sample back across the Atlantic to the
EBI, where the researchers soaked the DNA in water to reconstitute it
and used standard sequencing machines to unravel the code. They
recovered and read the files with 100-percent accuracy.
The work follows a big step last year when scientists at Harvard
announced they had stored 700 terabytes of data - enough for around
70,000 movies - in a gram of DNA.
The new method eliminates the risk of error when the DNA is read, say the researchers, whose work appears in the journal
Nature.
"We figured, let's break up the code into lots of overlapping
fragments going in both directions, with indexing information showing
where each fragment belongs in the overall code, and make a coding
scheme that doesn't allow repeats," said co-author Ewan Birney.
"That way, you would have to have the same error on four different fragments for it to fail, and that would be very rare."
Data is accumulating massively around the world, and storing it
is a headache. Magnetic and optical discs are voluminous, need to be
kept in cool, dry conditions and are prone to decay.
"The only limit (for DNA storage) is the cost," said Birney.
Sequencing and reading the DNA takes a couple of weeks with
present technology, so it is not suitable for jobs needing instant data
retrieval.
Instead, it would be appropriate for data that would be stored
for between 500 and 5,000 years, such as a doomsday encyclopaedia of
knowledge and culture.
But on current trends, sequencing costs could fall by a factor
of 20 within a decade, making DNA storage economically feasible for
timeframes of less than 50 years, the authors claim.
Source: Agency France-Presse
