Bridging energy and proteome allocation models allows prediction of the resource cost of traits across environments

Many traits divert resources from reproduction and are costly due to the physiological trade-offs organisms face. These traits might require the allocation of different resources, e.g., energy expenditure or production of macromolecules, and it is unclear how their costs can be compared given their different units. Moreover, the effect of environmental conditions and genetic background on the cost of traits is not well understood. Two different frameworks have been proposed to quantify the resource costs of traits, focusing on either energy allocation or proteome allocation. These frameworks implicitly assume energy provisioning or protein production limits growth, respectively, but the connection between the two limitations has been underexplored. To better connect these frameworks, we develop a framework that considers limitations in energy provisioning and macromolecule biosynthesis simultaneously to quantify and compare the cost of traits that require different resources. Using this model, we explore how environmental quality and genetic background affect the cost of traits. Notably, our model predicts that increasing food quality increases the cost of traits that require the production of new structures, while decreasing the cost of traits requiring energy expenditure. Moreover, our model makes novel predictions about the effect of degradation, recycling, and energetic demands for maintenance on the relationship between the macromolecular composition of the cells and growth rate (also known as bacterial growth laws).