Arroyo, J.I. (2020). Thermodynamics, metabolic ecology, and microbial community genomics. Doctoral dissertation. Pontifical Catholic University of Chile.

The metabolic theory of ecology (MTE) integrates fundamental physical principles to predict biological times, rates, and properties at different levels of organization, based on body size and temperature. Here we extend the MTE by suggesting an alternative model of temperature dependence and making new predictions. In the first chapter, based on the Eyring-Polanyi equation, we derive a mechanistic but simple (three-parameter) model for temperature dependence and show how its integration with other simple chemical kinetics models allows us to predict thermodynamic parameters. The predictions of this model were supported by data from a hundred temperature response curves at different levels of organization. In the second chapter, using the general temperature dependence model derived in chapter 1, we integrate principles of metabolic ecology, macroecology, and DNA sequencing theory (the basis of metagenomics) to derive a theoretical framework for the genomic community structure of microbiomes in natural and host-associated environments, in both ectotherms and endotherms (whose body temperature varies between species). This model was supported by data from global microbiome projects. In the third chapter, we evaluated some of the predictions from chapter 2 (such as the temperature dependence of species richness, genes, and metabolisms) in microbiomes from hot springs on a global scale. These data also supported the predictions, and we further showed that other variables such as pH explain the microbial metagenomic structure.