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Abstract

Coordinated dynamics of individual components in active matter are an
essential aspect of life on all scales. Establishing a comprehensive,
causal connection between intracellular, intercellular, and macroscopic
behaviors has remained a major challenge due to limitations in data
acquisition and analysis techniques suitable for multiscale dynamics.
Here, we combine a high-throughput adaptive microscopy approach with
machine learning, to identify key biological and physical mechanisms
that determine distinct microscopic and macroscopic collective behavior
phases which develop as Bacillus subtilis swarms expand over five orders
of magnitude in space. Our experiments, continuum modeling, and
particle-based simulations reveal that macroscopic swarm expansion is
primarily driven by cellular growth kinetics, whereas the microscopic
swarming motility phases are dominated by physical cell-cell
interactions. These results provide a unified understanding of bacterial
multiscale behavioral complexity in swarms.