Switching and Torque Generation in Swarming E. coli

作者：Katie Ford, Jyot D. Antani, Aravindh Nagarajan, Madeline M. Johnson, Pushkar P. Lele · 发表于：Frontiers in Microbiology · 年份：2018 · DOI：10.3389/fmicb.2018.02197 · 被引用次数：19 · 研究领域：Micro and Nano Robotics、Diffusion and Search Dynamics、Lipid Membrane Structure and Behavior

Escherichia coli swarm on semi-solid surfaces with the aid of flagella. It has been hypothesized that swarmer cells overcome the increased viscous drag near surfaces by developing higher flagellar thrust and by promoting surface wetness with the aid of a flagellar switch. The switch enables reversals between clockwise (CW) and counterclockwise (CCW) directions of rotation of the flagellar motor. Here, we measured the behavior of flagellar motors in swarmer cells. Results indicated that although the torque was similar to that in planktonic cells, the tendency to rotate CCW was higher in swarmer cells. This suggested that swarmers likely have a smaller pool of phosphorylated CheY. Results further indicated that the upregulation of the flagellin gene was not critical for flagellar thrust or swarming. Consistent with earlier reports, moisture added to the swarm surface restored swarming in a CCW-only mutant, but not in a FliG mutant that rotated motors CW-only (FliGCW). Fluorescence assays revealed that FliGCW cells grown on agar surfaces carried fewer flagella than planktonic FliGCW cells. The surface-dependent reduction in flagella correlated with a reduction in the number of putative flagellar preassemblies. These results hint towards a possibility that the conformational dynamics of switch-proteins play a role in the proper assembly of flagellar complexes and flagellar export, thereby aiding bacterial swarming.