Machinery of Anaerobic Butane Oxidation-Sulfate Reduction in Deep-Sea Microbial Consortia

The microbial process of butane anaerobic oxidation transforms deep-sea geological butane emissions to CO2, preventing the escape of the hydrocarbon into our atmosphere [1]. These microbes form consortia composed of two archaea releasing electrons from butane oxidation and a bacterial partner directing the electron flux towards sulfate reduction. The electron flow has been proposed to be directed by nanowire pili formed by cytochromes [2]. The process, close to the thermodynamic equilibrium, would offer fantastic perspectives in green carbon cycling technology by converting CO2 to butane with electricity [3]. To understand the overall reaction at the molecular level, we extracted the whole proteome from a decade-old microbial enrichment. The soluble catabolic enzymes catalyzing butane oxidation and sulfate reduction, together with cytochrome nanowires, have been fractionated, identified, and frozen on EM grids for structural characterization.