Decoding adaptive push–pull–wrap motility in the squid symbiont Vibrio fischeri

Bacteria navigate highly structured and dynamic environments, yet most studies examine only a handful of model organisms under simplified conditions. The squid symbiont Vibrio fischeri offers a powerful system to study adaptive motility in complex settings. During colonization of the Hawaiian bobtail squid (Euprymna scolopes), V. fischeri uses a striking “push-pull-wrap” locomotion strategy to navigate diverse physical landscapes, including bulk seawater, viscoelastic mucus, and confined ducts. Here, we leverage high-speed 3D fluorescence microscopy and optical trapping to capture swimming trajectories and flagellar dynamics of a wild-type V. fischeri strain ES114 isolated from the light organ of E. scolopes. We apply a data-driven switching dynamical systems framework to reveal how physical parameters such as viscosity and confinement modulate V. fischeri’s motility states and transitions between them. This approach connects flagellar mechanics to observable motility behavior and provides a predictive tool for understanding bacterial navigation in complex environments. By enabling quantitative analysis of adaptive motility, it lays the groundwork for studying locomotion strategies in other emerging model organisms.