Gliding Motion of Diatoms: Motors, Filaments, and Dynamic Trajectory Control

Raphid diatoms exhibit rapid gliding motility with remarkable directional flexibility, yet the underlying mechanisms remain poorly understood. Using Craspedostauros australis as a model, we combine phylogenomics, live-cell imaging, and high-resolution microscopy to dissect both force generation and trajectory control. We find that raphe-associated actin bundles do not show directional turnover, arguing against a direct role of actin dynamics in force production. Instead, we identify diatom-specific myosins (CaMyoB-D) that display coordinated movement during gliding, consistent with a motor function. At the cellular level, diatoms dynamically modulate their trajectories by switching between one- and two-raphe contact with the substrate. This switching controls path curvature, with single-raphe gliding producing curved paths and dual-raphe gliding resulting in straighter motion. Together, our results suggest a mechanism in which myosin-driven force generation is coupled to dynamic regulation of cell-substrate contact, enabling flexible navigation in complex environments.