Mathematical modeling related to bacterial gliding mechanism at low Reynolds number with Ellis Slime

The self-propelling mechanism of rod-shaped bacteria over complex rheological slime is vital. These bacteria glide near the surface by producing waves in their body and secrete an extracellular polymeric substance (EPS) that allows them to move without flagella. During gliding motion, bacteria experience hydrodynamic interactions with complex rheological fluid attached to the surfaces which are either rigid or soft. Their natural response to such interactions affects their gliding speed and power required for propulsion. Motivated by this fact, we investigate the fundamental mechanics of bacterial locomotion by utilizing an undulating surface model combined with the Ellis fluid model. The substrate beneath the organism is considered a wavy (soft substrate) or a rigid surface. The equations of motion are reduced into a single ordinary differential equation under the lubrication approximation. A numerical solution of this equation is computed via the MATLAB bvp5c routine. The code is adjusted in such a way that it refines the unknowns, i.e., flow rate and gliding speed by employing a modified Newton-Raphson algorithm until the satisfaction of equilibrium conditions. The computed pairs of speed and flow rate are then utilized to compute the energy consumed by the glider. Work done by the glider, gliding speed, flow rate, velocity of the slime, and streamlines patterns are also visualized by graphs.

Automated summary

The self-propelling mechanism of rod-shaped bacteria over complex rheological slime is vital. In this study, the fundamental mechanics of bacterial locomotion were investigated using an undulating surface model combined with the Ellis fluid model. The results showed the impact of hydrodynamic interactions on gliding speed, power, and energy consumption of the bacteria.