Dynamic energy allocation model for microbial growth control and morphogenesis

Efficient allocation of energy resources to key physiological functions allows living organisms to grow in diverse environments and adapt to a wide range of perturbations. To quantitatively understand how unicellular organisms utilize their resources in response to changes in their environment, we introduce a theory of dynamic energy allocation which describes microbial growth dynamics based on partitioning of metabolizable energy into key physiological functions: growth, division, cell shape regulation, energy storage, and loss through dissipation. By optimizing the energy flux for growth, we derive the general equations governing the time-evolution of bacterial cell morphology and growth rate. The resulting model accurately captures experimentally observed dependencies of bacterial cell size on growth rate, superlinear scaling of metabolic rate with cell size, and predicts nutrient-dependent trade-offs in energy expenditure. By calibrating model parameters with experimental data for the model organism E. coli, our model is capable of describing bacterial growth control in dynamic conditions such as nutrient shifts and osmotic shocks. The model captures these perturbations with minimal added complexity and our unified approach predicts the driving factors behind a wide range of observed morphological and growth phenomena.