  The Bacillus subtilis Spo0J/Soj proteins, implicated in chromosome
segregation and transcriptional regulation, show striking dynamics: Soj
undergoes irregular relocations from pole to pole or nucleoid to nucleoid. Here
we report on a mathematical model of the Soj dynamics. Our model, which is
closely based on the available experimental data, readily generates dynamic Soj
relocations. We show that the irregularity of the relocations may be due to the
stochastic nature of the underlying Spo0J/Soj interactions and diffusion. We
propose explanations for the behavior of several Spo0J/Soj mutants including
the "freezing" of the Soj dynamics observed in filamentous cells. Our approach
underlines the importance of incorporating stochastic effects when modelling
spatiotemporal protein dynamics inside cells.
