[ODP-051/W3-6] The directional switching of flagellar rotation affected by mutations in the stator protein PomA
The bacterial flagellar motor can rotate bi-directionally in counter-clockwise (CCW) and clockwise (CW) directions. The motor rotates at CCW in default, whereas when receiving a repellent chemotaxis signal, it rotates at CW. The motor is composed of a stator part and a rotor part. The stator unit is composed of a pentameric barrel of A subunits and a dimer axis of B subunits. Our recent study showed that highly conserved charged and neighboring residues of the A subunit are located close to the rotor for torque generation. It is hypothesized that the site of the stator gear which meshes with the that of rotor determine the rotational direction. The rotational direction is controlled by chemotaxis signaling transmitted to the rotor. However, there are only few reports that the stator is involved in the switching of the rotation direction. Here, we found novel mutations that affect the switching frequency of the rotational direction in pomA. They were located at the putative interaction surface of the stator with the rotor. We show that the appropriate interaction between the stator and rotor is critical for controlling the rotational direction of the flagellar motor.