Bacterial swimmers with a polar flagellar bundle: pull, push, and wrapping

Flagellated bacteria swim in a fluid environment by rotating motors embedded in the cell membrane and consequently rotating helical flagella. Swimming strategies of such bacteria vary depending on the number of flagella and their arrangement across the cell body. In this talk, we present a mathematical model of lophotrichous bacteria such as Pseudomonas putida that have multiple flagella at one polar end. P. putida undergo a classical event of pull-wrapping-push cycle. To investigate the fluid-cell interaction, we explicitly model the cell as a neutrally buoyant rigid body, treat the flagella as helical elastic rods modeled by a nonstandard Kirchhoff rod theory, and couple the bacterium to a viscous fluid with the regularized Stokes formulation. The simulation results may provide the insight into the underlying swimming mechanism of lophotrichous bacteria.