Dynamic instability of force-generating bacterial microtubules

Summary Dynamic instability refers to the ability of cytoskeletal polymers to switch between growing and shrinking phases. This phenomenon has been extensively studied for eukaryotic microtubules which consist of 13 protofilaments. Here we report on the dynamic properties of prokaryotic microtubules found in Prosthecobacter bacteria, which consist of 4-5 protofilaments and, like their eukaryotic counterparts, display dynamic instability. Using microfabricated barriers we show that the catastrophe rate of bacterial microtubules increases when their growth is stalled by a rigid barrier. We find that the lifetime distributions of both free and stalled bacterial microtubules can be fitted using the same phenomenological model that we previously introduced for eukaryotic microtubules, suggesting that bacterial microtubules may be considered a model system for eukaryotic microtubules. We further use cryo-electron tomography to reveal structural details of dynamic ends and show that bacterial microtubules may form doublets similar to axonemal microtubules in eukaryotes.