Hydration-dehydration cycles drive compartment dynamics in minimal protocells

Summary Compartmentalization is a defining feature of cellular systems, yet how early compartments could undergo repeated cycles of growth, division, and content organization without complex chemistry remains unresolved. Here we study a minimal membrane-based system subjected to periodic hydration– dehydration cycles, mimicking fluctuating physical environments on the early Earth. We show that cyclic environmental conditions alone drive a sequence of reproducible compartment dynamics, including macromolecule encapsulation, membrane growth, division, and the generation of a highly crowded interior. These processes emerge from biophysical transformations of a single-component membrane and do not require any chemical reactions or metabolic activity. Importantly, compartments retain their structural integrity across multiple cycles, enabling repeated encapsulation without loss of individuality. Our results demonstrate that fluctuating physical conditions can be transduced by membrane biophysics into sustained, cell-like cycles, challenging the view that primordial cellular dynamics necessarily required chemically driven growth and division. Competing Interest Statement The authors have declared no competing interest.