Controlling the rotational behavior of bacterial flageller motors

Mutant strains of bacterial flagellar motors can be tethered to the sidewalls of microfluidic channels to perform mechanical functions. In most cases, the rotational behavior of the tethered motors must be properly controlled in order to achieve optimized performance. There are several approaches for carrying out this task but most of them involve techniques that affect the viability of the motors. The present paper describes the application of hydrodynamic loading to achieve cell rotation synchronization. This is a non-contact method that uses viscous drag force induced by a small fluid flow to either slow down or stop the motor rotation completely if necessary. No negative effect on the motors is observed when the loading time is kept short. By applying this method to a group of tethered motors, it is possible to stop and restart their rotation for the purpose of synchronization.