DNA engineers are apparently on a quest to belittle my fears, starting with arachnophobia (see Stojanovic’s nano-spiders, JACS 128, 12693, 2006). The next strike is the assembly of nano-germs by a team of partially certified geniuses.

Inspired by Rickettsia rickettsii, a bacterium which propels itself inside host cells by polymerizing a “comet tail” of actin filament, Venkataraman et al. invented a sequence of DNA hybridization reactions which lead to the polymerization of double-stranded DNA segments between two DNA strands termed “anchor” and “Rickettsia”. Native gels and AFM imaging are employed to prove that Rickettsia is pushed away from anchor as envisioned.

This proof-of-principle experiment raises intriguing engineering questions. Now that we can build a DNA polymerization motor and don’t have to rely on actin or tubulin, the question becomes: “Should we?”, and: “Does the presented DNA adaptation capture the essence of actin polymerization also with respect to mechanics and kinetics?”

In addition to its interesting science, the paper deserves critical attention due to the raw beauty of Figure 5b, which would not be out of place in the galleries of Lascaux.