Helicase and helicos

The Nature cover this week highlights the work on the helicase activity of the ribosome from Carlos Bustamante's lab*, mentioned here previously. It's a cute picture, complete with little tweezers.

Also, I previously noted some work out of Steve Quake's lab via his company, Helicos, on single molecule sequencing, but noted, "I don't really know much about how this thing performs in the field, and how many of these they've sold." Well, the proof is in the pudding, and they just published a paper in which they demonstrate their instrument by sequencing the genome of the M13 virus, which is about 7 kb. They manage an average read length of about 25 bases, which is comparable to the 2005 work by the Church lab using emulsion PCR, where they achieved read lengths of 26 bases, but far below the 200 - 300 base read lengths claimed by 454. Of course, neither of these latter technologies are single-molecule based, but it's not clear what advantages accrue to the Helicos system by dint of being single-molecule based either. They clearly require a huge number of "single molecule" reads in order to actually sequence a genome, so the potential for scalability is not clear to me.

And, finally, speaking of George Church, if you want to have the crap scared out of you, just look at the title of this paper: Bacteria Subsisting on Antibiotics.

*Not to be confused with Carlos D. Bustamante, as I recently found out.