Conversion of Escherichia coli to generate all biomass carbon from CO₂

The living world is divided into autotrophs that convert CO₂ into biomass and heterotrophs that consume organic compounds. Can we transform heterotrophs into autotrophs, producing all their carbon mass from CO₂? In spite of widespread interest for renewable energy storage and more sustainable food production, so far industrially-relevant heterophic model organisms could not be engineered to use CO₂ as the sole carbon source. Here we report the achievement of this transformation on laboratory timescales. We constructed and evolved Escherichia coli to produce all biomass carbon directly from CO₂. Reducing power and energy, but not carbon, is supplied via the one-carbon molecule formate, which can be produced electrochemically. Rubisco and phosphoribulokinase were co-expressed with formate dehydrogenase to enable CO₂ fixation and reduction via the Calvin-Benson-Bassham cycle. Autotrophic growth was achieved following several months of continuous laboratory evolution in a chemostat under intensifying organic carbon limitation and confirmed via isotopic labeling.