  In this paper, we analyze the electrotactic movement of Dictyostelium
discoideum from the viewpoint of non-equilibrium statistical mechanics. Because
we can observe fluctuating behavior of cellular trajectories, we analyze the
probability distribution of the trajectories with the aid of the fluctuation
theorem. Recently, the validity of the fluctuation theorem was verified in a
colloidal system, and it has also been applied to granular systems, turbulent
systems and chemical oscillatory waves to investigate some of their statistical
properties that are not yet completely understood. Noting that the fluctuation
theorem is potentially applicable to cellular electrotaxis, here we employ it
to help us obtain a phenomenological model of this biological system.
