Dependence of Reversal Rate in Myxococcus xanthus on Inter-Cell Contact

Abstract

We have investigated how reversal rate changes with time in swarms of Myxococcus xanthus in starvation conditions by examining the motion of every cell at each point in time for four hours. Over this time, we observed a 43% increase in reversal rate, with most of this increase occurring in the first 33 minutes of starvation. We also observed a marked shift in the composition of the swarm as the average cluster size experienced by a cell increased more than four-fold, and the fraction of cells completely covered by neighbors increased dramatically at the expense of cells with little or no coverage. The majority of this population shift also occurred in the first 33 minutes of starvation. Speed was nearly invariant with time for cells in the swarm. We show that reversal rate depends significantly on the fraction of a cell contacted by its neighbors in a nonlinear way, and use this to suggest a model of the interaction between A- and C-signaling and reversal events in the aggregation process in M. xanthus.