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Abstract
Most elemental cycles in Earth’s near-surface environment, including marine sediments, are mediated by microbial reactions. To quantify these transformations and predict the distribution of chemical species, biogeochemical models need to capture the transport and reaction rates of these processes. Reactions of this nature often depend on environmental conditions, including the availability of substrates, as well as the microbial community present. Rate expressions then often involve numerous model parameters that may be site-specific or poorly constrained. To address this, we describe a novel approach to derive rate expressions and their parameterization using symbolic regression. In addition, we present model developments at the microscale to characterize nitrogen utilization and growth efficiency calculation in a microbial aggregate, comprised of methanotrophic archaea (ANME) in syntrophic association with sulfate-reducing bacteria (SRB). We demonstrate model agreement with observed growth efficiencies when using ammonium and investigate potential triggers for N2 fixation activity in these consortia.