(262e) Diffusion of an Ellipsoid in Bacterial Suspensions

Active matter such as swarming bacteria and motile colloids exhibits exotic properties different from conventional equilibrium materials. Among these features, the enhanced diffusion of tracer particles is generally deemed as a hallmark of active matter. Here, rather than spherical tracers, we investigate the diffusion of isolated ellipsoids in quasi-two-dimensional bacterial bath. Our study reveals a nonlinear enhancement of both translational and rotational diffusion. More importantly, we uncover an anomalous mode of coupling between translation and rotation that is strictly prohibited in normal Brownian motion. Combining experiments with theoretical analysis, we show that such an anomaly arises from a subtle bacteria-particle interaction. Our work sheds new light on fundamental transport processes in microbiological systems and provides important insights into organizing principles of active matter.