Phase separation dynamics explains \emph{Myxococcus xanthus} aggregation

The soil-dwelling bacteria \emph{Myxococcus xanthus} exhibits a wide range of self-organizing social behaviors during its developmental cycle. When nutrients are scarce, \emph{M. xanthus} cells aggregate into multicellular structures and eventually form massive clusters called fruiting bodies, where cells sporulate as a self-preservation mechanism. In light of recent advancements in active matter theory, we identify the aggregation process of \emph{M. xanthus} as a spinodal decomposition phase separation. We show that without long-range communication, local mechanical interactions are sufficient to drive the system out of equilibrium. \emph{M. xanthus} cells actively modulate their gliding motility and reversal rate to cross a boundary in the P\'{e}clet~Number-density phase plane to achieve phase separation.