Integrated Proteomics and Metabolomics Reveal Altered Metabolic Regulation of Xanthobacter Autotrophicus Under Electrochemical Water-Splitting Conditions

Biological-inorganic hybrid systems are a growing area of study seek to combine microorganisms with abiotic materials for purposes such as chemical synthesis, environmental remediation, and energy generation. Recently, hybrid systems have been developed toward the sustainable generation of value-added chemicals from only electricity, water, and air. These hybrid systems typically consider microorganisms as catalysts that perform only the reaction of interest, however unaccounted for metabolic activity may influence that reaction and the overall system output. The investigation of biological responses to the hybrid environment is thus critical to future system development and optimization. The present study investigates this phenomenon in a system that uses electrochemical water-splitting to provide reducing equivalents to the nitrogen-fixing bacteria Xanthobacter autotrophicus for the reduction of N2 to biomass that may be used as fertilizer. Using integrated proteomic and metabolomic methods, we have found differentiated metabolic regulation under electrochemical water-splitting conditions. We further report an increased expression of certain key proteins, including those responsible for nitrogen fixation and assimilation, that indicate increased rates of nitrogen fixation and support previous findings of accelerated biomass accumulation under electrochemical water-splitting conditions. This work presents a challenge to an inert catalyst view of microorganisms in biological-inorganic hybrid systems while demonstrating the power of multi-omics analysis as a tool for detailed analysis of those systems.