Motile cells move in response to environmental cues, and have complex networks that allow them to change their direction accordingly. The rod-shaped bacterium Myxococcus xanthus controls its motility by switching its own polarity from the front (leading) to the back (lagging) end depending on which direction it is headed, meaning that the mechanisms controlling movement are able to switch rapidly. A recent paper finds that the leading side of the cell accumulates a protein called MglA, while MglB is found at the lagging end of the cell where it inactivates MglA. Image above shows MglB (green) on the lagging end of a bacterium, even after it changes direction (middle of image).
Reference: Yong Zhang, Michel Franco, Adrien Ducret, Tâm Mignot. Authors’ PLoS Biology paper can be found here.