Myxococcus xanthus is Gram-negative, rod-shaped bacteria, with a very complex social life-style. These bacteria are able to move on surfaces along its long axis with defined leading and lagging cell poles. Upon cellular reversals the previous lagging pole becomes the new leading pole and the polarity axis is switched.
Underlying this process are two coupled modules: the Frz Chemosensory System and the Polarity Module. The Frz Chemosensory System is responsible for regulating reversal frequency. Downstream of this system is the Polarity Module. Its core is composed of two proteins: MglA, a small Ras-like GTPase, and MglB, its cognate GTPase activating protein. During movement, MglA is located at the leading pole where it coordinates cell movement, whereas MglB is mostly located at the lagging pole. Reversals triggered by the Frz system induce MglA relocation to the new leading pole and MglB to the new lagging pole. A third protein, the response regulator RomR, also plays a role in this process as previous evidence suggests that it may constitute a link between Frz-signaling and MglAB polar oscillations. The localization of these three proteins is interdependent.