Nanotubes: Shaking Hands, Talking, or Sharing?

differentiation to produce a dormant spore (Meisner et al., 2008). Contact-dependent inhibition is a reversible, contact-dependent means by which strains of E. coli induce a nonreplicating state in susceptible cells through direct transfer of two effector proteins (Aoki et al., 2005). These three mechanisms are all characterized by the specific transfer of a limited number of signals in response to highly specific environmental cues between cells of the same species. However, bacteria can also communicate with other species. The first, and best-known, form of interspecies contactdependent trafficking is conjugation. Most conjugative plasmid transfer is restricted to specific species, but a subset of promiscuous plasmids can transfer between many different species and have a broad-host-range specificity (Thomas and Nielsen, 2005). Thus, although the substrate transferred is very specific, there is a relaxed specificity for recipients, which can be almost any bacterium or even eukaryotic cells (Buchanan-Wollaston et al., 1987; Heinemann and Sprague, 1989). Symbiotic relationships based on syntrophy also provide examples of inter-species contact-dependent communication (Ishii et al., 2005; Shimoyama et al., 2009). In the February 18th issue of Cell, Sigal BenYehuda’s group now describes a new form of inter-bacterial communication: the transfer of cytoplasmic constituents through novel structures termed nanotubes. Remarkably, in contrast to the systems described above, there is no specificity in terms of the translocated substrate, the direction of transfer, or the species it is delivered to (Dubey and Ben-Yehuda, 2011). In their potentially ground-breaking paper, Dubey and Ben-Yehuda (2011) show that Bacillus subtilis cells grown on solid medium can transfer multiple cytoplasmic contents to neighboring cells. They showed that B. subtilis could transfer green-fluorescent protein (GFP), the non-genetically Nanotubes: shaking hands, talking, or sharing?