Implementation of a Reductive Route of One-Carbon Assimilation in Escherichia coli through Directed Evolution

Abstract : Endowing biotechnological platform organisms with new carbon assimilation pathways is a key challenge for industrial biotechnology. Here we report progress toward the construction of formatotrophic Escherichia coli strains. Glycine and serine, universal precursors of one-carbon compounds oxidized during heterotrophic growth, are produced from formate and CO2 through a reductive route. An adaptive evolution strategy was applied to optimize the enzymatic steps of this route in appropriate selection strains. Metabolic labeling experiments with 13C-formate confirm the redirected carbonflow. These results demonstrate the high plasticity of the central carbon metabolism of E. coli and the applicative potential of directed evolution for implementing synthetic pathways in microorganisms.