Pacific Biosciences and the 15-minute genome

36 megabases an hour

Turner pointed out several key advantages of the SMRT system. Each nucleotide carries its fluorescent tag at the very end of the molecule, such that the tag is cleaved away and not incorporated into the growing DNA strand.

And because the system is a close facsimile to in vivo DNA synthesis, the read lengths will be comparable to Sanger sequencing – hundreds or thousands of contiguous bases – thus avoiding the bioinformatics challenges of assembling very short reads. Moreover, there are no moving parts, aside from the polymerase itself, once a run is started.

Turner presented preliminary data on synthetic DNA templates. He presented CCD images showing a grid of 1000 ZMWs on a chip smaller than a pinkie fingernail, which burst into fluorescent life when all the necessary ingredients were presented to the enzymes sitting in each well.

That's a throughput of 36 megabases an hour. (The video had to be slowed down, because the human eye wouldn't be able to register the images in real time.) "No-one's ever seen 1000 polymerases making DNA before in real time," Martin says.

Although PacBio is still a couple of years at least from debuting its instrument, Turner outlined several future enhancements that will, he predicts, deliver the 15-minute human genome.

First, produce a chip with one million ZMWs (no bigger than the current prototype, which only uses 0.1 per cent of the available real estate). Second, increase the speed of DNA polymerisation from 10 to 50 bases per second – the limiting factor here is not the enzyme but the detection capability.

And finally, use a 20-megapixel CCD camera with on-chip magnification to make it single-photon sensitive. Both of these technologies exist now, he says: they just have to be brought together.

The projected output with these enhancements, in about five years' time, is 100 gigabases an hour. "This is what is required to get genome sequencing into routine medical practice," says Turner.

"It is disruptively faster than current next-generation technologies. Instead of being hours per base, it's bases per second."

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