Return of the Sword-Bearer
Last year I wrote about a very obscure bacterium called Ensifer. Its name means “the sword-bearer” because it has a rod with which it appears to stab and kill other bacterial cells. I suggested that this was a Type VI Secretion System (T6SS – Hello Marek!). I still think that is what it is, although Marek Basler expressed doubts, and he is an expert.
The other day, I came across another paper about T6SS. The bacteria involved were Pseudomonas aeruginosa and Salmonella enterica (both gammaproteobacteria), and Burkholderia thailandensis (a betaproteobacterium). None of them were rhizobia, so I would not ordinarily mention it here, but I was struck by the title: ” Quantitative single-cell characterization of bacterial interactions reveals type VI secretion is a double-edged sword”.
So, the sword-bearer returns. As far as I can tell, the authors were not literally thinking of the physical structure as a sword. They observed that the deployment of the T6SS made the bearer more susceptible to attack by the T6SS of other cells, and described this as a “double-edged sword” in a purely abstract metaphor meaning a weapon that can also injure the holder. I like to think, though, that Ensifer had seeped into their subconscious.
LeRoux, M., De Leon, J.A., Kuwada, N.J., Russell, A.B., Pinto-Santini, D., Hood, R.D. et al. Quantitative single-cell characterization of bacterial interactions reveals type VI secretion is a double-edged sword. Proceedings of the National Academy of Sciences 109: 19804-19809. http://dx.doi.org/10.1073/pnas.1213963109