Control of Multicellular Magnetotactic Bacteria with a Magnetic Field

Bacteria of the species Magnetoglobus multicellularis form spherical colonies composed of tens of cells. A colony moves as a single unit as each cell rotates its flagella. Magnetic minerals within each cell cause the direction of the colony’s motion to align with the ambient magnetic field. Here we characterize the motion of these large, fast-swimming colonies both individually and collectively in an oscillating magnetic field. First, we observe the dynamics of individual colonies. We measure their swimming speed, magnetic moment, and diffusion coefficient.
Next, we observe the collective motion of dense swarms of colonies in a rotating magnetic field. We compare the these observations to the predictions of a simple model. We use these results to propose a method to direct swarms of swimming colonies to perform tasks, such as sorting tracer particles in a fluid.