Length heterogeneity of flexible bacteria enhances swarming

Bacterial swarming is a phenomenon characterized by the rapid migration of microorganisms on a surface powered by flagella. While extensive studies have explored various factors influencing swarming dynamics, the impact of length variation within a single strain on swarming remains to be elucidated. Here, we investigate the effect of length variants within a single strain, Vibrio alginolyticus, as an ideal model to explore the cooperative mechanisms driven by a heterogeneous, flexible population. Through individual cell tracking, we found that cell length directly impacts collective organization. Long, flexible cells move faster and more persistently than shorter cells, promoting the emergence of large-scale, coordinated flow. In contrast, shorter cells slow down due to frequent reverse movements, which create spaces and prevent jamming within the dense colony. This division of labor, where longer cells act as leaders and shorter cells serve as buffers, facilitates efficient collective movement and demonstrates the significant advantage of phenotypic heterogeneity within a single strain for robust swarming. Our findings suggest that the diversity in length of active matter may facilitate efficient spreading across soft interfaces.