Emily Zakem , Martin Polz, Mick Follows

Microbial activity mediates the global flow of carbon, oxygen, nitrogen, and other elements, including climatically significant gases. However, non-photosynthetic microbial activity is typically not resolved dynamically or mechanistically in global models of the marine and terrestrial biospheres, inhibiting predictive capability. Understanding the global-scale impact of complex microbial community activity requires a consistent framework with which to constrain the parameterizations of diverse metabolisms. Here, we describe how the key redox chemistry underlying specific metabolisms can be exploited to parameterize diverse metabolic strategies. By quantitatively relating metabolic yields to chemical gradients, the growth and respiration of microbial biomass is systematically related to stoichiometries of substrate consumption, oxidation, and reduction that constitute biogeochemical fluxes. Linked with parameterizations of resource acquisition rates, whole organism metabolism can be integrated into trait-based modeling frameworks as metabolic functional types. Benefits of this approach include prognostic metabolic biogeography and what we term `gene-fluent’ predictions of community metabolism. The theoretically grounded, electron-balanced framework progresses the description of microbial ecosystems towards conservation of energy as well as mass.