Motility
M. xanthus cells exhibit a type of surface-mediated motility known as twitching motility. Twitching is mediated by a Type IV pilus that extrudes through the pole of the cell. The pilus is extended by the addition of pilin monomers at the base of the pilus. The tip of the pilus binding to a substrate in the biofilm sends a signal for the pilus to retract by the removal of pilin subunits. The shortening of the pilus leads to the cell being dragged along the surface towards the tip of the pilus. The mechanism of the Type IV pilus has been likened to a grappling hook. The pilus apparatus is only constructed at one pole at a given time, but the location is dynamic and dependent upon chemotactic signals.
In addition to Type IV pilus mediated group motility, M. xanthus cells also move individually using gliding motility on solid surfaces. Cells move in one direction along their long axis, then pause and continue movement in the opposite direction. The molecular mechanisms driving gliding motility are currently unknown.
Read more about this topic: Myxococcus Xanthus