Modeling E coli. Motility through Viscoelastic Networks in Stokes Flow

E. coli bacteria swim and maneuver through complex fluid environments such as porous media containing polymeric filaments called viscoelastic networks. Because such bacteria can impact humans by causing sickness or contaminating water sources, researchers are motivated to understand how moving through viscoelastic networks affects bacteria trajectory and velocity. Using the method of regularized Stokeslets we model an E. coli cell initially encapsulated in a viscoelastic network. We vary network parameters to see how an E. coli cell would be affected in terms of its trajectory, velocity, efficiency, and power. We quantify the effect of the cell on the network by measuring the network’s deformation and potential energy relative to equilibrium. We found that pore size and number of layers have a strong influence on the interaction between the cell and the network. For example, sometimes the network has a positive effect on the cell, increasing its velocity, and other times it has a negative effect on the cell, decreasing its velocity. Our model allows us to better understand cell-viscoelastic network-fluid interactions and suggests different possibilities to design experiments using viscoelastic fluids with tunable properties that bacteria could swim in.