 The optimal allocation of cellular resources between protein synthesis and metabolism is essential for microbial growth. A new model has been developed which accurately predicts the growth rate of bacteria under different conditions. The model uses only a few biological parameters to explain the wide range of growth phenomena observed in and out of steady state. This suggests that the optimal flux regulation of metabolic and translational fluxes is key to understanding how cells adapt to changing environments. This article was authored by Griffin Chaw and Jonas Kramer.