Dynamics in the Dual Fuel Flagellar Motor of Shewanella oneidensis MR-1

The stator is an eminent component of the flagellar motor and determines a number of the motor's properties, such as the rotation-energizing coupling ion (H⁺ or Na⁺) or the torque that can be generated. The stator consists of several units located in the cytoplasmic membrane surrounding the flagellar drive shaft. Studies on flagellar motors of several bacterial species have provided evidence that the number as well as the retention time of stators coupled to the motor is highly dynamic and depends on the environmental conditions. Notably, numerous species possess more than a single distinct set of stators. It is likely that the presence of different stator units enables these bacteria to adjust the flagellar motor properties and function to meet the environmental requirements. One of these species is Shewanella oneidensis MR-1 that is equipped with a single polar flagellum and two stator units, the Na⁺-dependent PomAB and the H⁺-dependent MotAB. Here, we describe a method to determine stator dynamics by fluorescence microscopy, demonstrating how bacteria can change the composition of an intricate molecular machine according to environmental conditions.