Review article from the ERA Chair and collaborators from LanzaTech and The University of Queensland published in the top journal Metabolic Engineering provides a comprehensive overview of advances in systems metabolic engineering of autotrophic carbon oxide-fixing biocatalysts towards a circular economy. The review focuses on biochemical identification of pathways, components, and activities; redox, energy, carbon, and electron balancing; thermodynamics and fluxes; regulatory mechanisms; and genotype-phenotype links in the key chemolithoautotrophic biocatalysts acetogens and hydrogenotrophs. Aspects of genetic engineering of cell factories and industrial gas fermentation are also covered.