Motility of \textit{Escherichia coli} in a quasi-two-dimensional porous medium

Abstract

Bacterial migration through confined spaces is critical for several phenomena like: biofilm formation, bacterial transport in soils, and bacterial therapy against cancer . In the present work, \textit{E. coli} (strain K12-MG1655 WT) motility was characterized by recording and analyzing individual bacterium trajectories in a simulated quasi-2-dimensional porous medium. The porous medium was simulated by enclosing, between slide and cover slip, a bacterial-culture sample mixed with uniform 2.98 $\mu m$ spherical latex particles. The porosity of the medium was controlled by changing the latex particle concentration. By statistically analyzing trajectory parameters like: instantaneous velocity and turn angle, as well as mean squared displacement, we were able to quantify the effects that different latex particle concentrations have upon bacterial motility. To better understand our results, bacterial trajectories were simulated by means of a phenomenological random-walk model (developed ad hoc), and the simulated results were compared with the experimental ones.