Fig. 7: Crawling model.
a Two-state model for crawling. Adhesins (e.g., OMPs and LPS) bind to kidney cells via a spring. The release of the adhesin-surface bond depends on the spring extension (x) by the bacterial movement. b Qualitative prediction of the dependence of the fraction of bound adhesins on \({k}_{{{{{{{{\rm{off}}}}}}}}}^{{\prime} }/{k}_{{{{{{{{\rm{on}}}}}}}}}\). The inset shows accumulative displacements calculated by setting different values of \({k}_{{{{{{{{\rm{off}}}}}}}}}^{{\prime} }/{k}_{{{{{{{{\rm{on}}}}}}}}}\). The averages of 10 runs are shown. c The dependence of vCR/v0 on \({k}_{{{{{{{{\rm{off}}}}}}}}}^{{\prime} }/{k}_{{{{{{{{\rm{on}}}}}}}}}\). Based on the assumption of Nad ≪ Nr (i.e., \({N}_{{{{{{{{\rm{ad}}}}}}}}}^{{\prime} }={N}_{{{{{{{{\rm{ad}}}}}}}}}\)), calculations were performed using \({N}_{{{{{{{{\rm{ad}}}}}}}}}^{{\prime} }=\)1000 (gray), 2500 (red), or 5000 (blue). The averages of 10 runs are shown. d The upper schematic shows that a bacterium experiences a spatial change based on the density of host receptors (Nr). The lower panel demonstrates the change in the crawling speed with the variation of Nr. The simulations were performed using \({k}_{{{{{{{{\rm{off}}}}}}}}}^{{\prime} }/{k}_{{{{{{{{\rm{on}}}}}}}}}\)= 0.5 and 0.03 along with the temporal variation of Nr.
