Asymmetric interactions and feast-famine cycles drive chaos in microbial populations.

Predicting the dynamics of ecological systems is a central challenge in biology. One factor that could contribute to limited predictability is the presence of ecological chaos. Theory has long suggested that even simple interactions could produce chaos, yet empirical demonstrations in living systems remain scarce. Here we show that chaos emerges naturally in a minimal microbial community exposed to feast-famine cycles. In a two-strain system of Escherichia coli, increasing the duration before replenishing resources reveals transitions from exclusion, to stable coexistence, to chaos, driven by asymmetric ecological interactions and periodic environmental forcing. A dynamical systems framework (under consumer-resource or much simpler generalized Lotka-Volterra models) both predicts and recapitulates these dynamics, confirming chaos under tractable laboratory conditions. Because feast-famine cycles and asymmetric interactions are widespread in nature, our findings provide a model for uncovering the ecological and evolutionary significance of chaos and reveal fundamental limits to predictability in living systems.