(99e) Multiflagellarity Stabilizes Bacterial Locomotion Against Buckling

The locomotion of flagellated bacteria in viscous fluid provides the blueprint for a number of micro-scale engineering applications. The elasticities of both the hook protein (connecting cell body and flagellum) and the flagella themselves play a key role in determining the stability of locomotion. We use a coarse-grained discretization of elastic flagella connected to a rigid cell body to examine trajectories and flow fields for free swimmers. We indeed find that hook and/or flagellar buckling occurs above a critical flexibility relative to the swimmer’s torque input. This renders straight swimming ineffective, though not necessarily undesirable in practice. Simulations with two flagella show bundling greatly stabilize the buckling effect. We also examine the impact of higher flagellar multiplicity on locomotion, finding that while the straight swimming speed is quite similar to the uniflagellar case, multiflagellar swimming is robust to random placement and resists buckling as well. Ultimately our results may provide insight on how swimmers move through complex environments and how to design microrobotic swimmers for specific applications.