Synthetic carbon fixation via the autocatalytic serine threonine cycle

Atmospheric CO 2 poses a major threat to life on Earth by causing global warming and climate change. On the other hand, it is the only carbon source that is scalable enough to establish a circular carbon economy. Accordingly, technologies to capture and convert CO 2 to reduced one-carbon (C 1 ) molecules (e.g. formate) using renewable energy are improving fast. Driven by the idea of creating sustainable bioproduction platforms, natural and synthetic C 1 -utilization pathways are engineered into industrially relevant microbes. The realization of synthetic C 1 -assimilation cycles in living organisms is a promising but challenging endeavour. Here, we engineer the autocatalytic serine threonine cycle, a synthetic C 1 -assimilation route in Escherichia coli . Our stepwise engineering approach in tailored selection strains combined with adaptive laboratory evolution experiments enabled the organism to grow on formate. The synthetic strain uses formate as the sole carbon and energy source and is capable of growing at ambient CO 2 concentrations, demonstrating the feasibility of establishing synthetic C 1 -assimilation cycles over laboratory timescales.