Functional reconstitution of a bacterial CO ₂ concentrating mechanism in E. coli

Many photosynthetic organisms employ a CO ₂ concentrating mechanism (CCM) to increase the rate of CO ₂ fixation via the Calvin cycle. CCMs catalyze ≈50% of global photosynthesis, yet it remains unclear which genes and proteins are required to produce this complex adaptation. We describe the construction of a functional CCM in a non-native host, achieved by expressing genes from an autotrophic bacterium in an engineered E. coli strain. Expression of 20 CCM genes enabled E. coli to grow by fixing CO ₂ from ambient air into biomass, with growth depending on CCM components. Bacterial CCMs are therefore genetically compact and readily transplanted, rationalizing their presence in diverse bacteria. Reconstitution enabled genetic experiments refining our understanding of the CCM, thereby laying the groundwork for deeper study and engineering of the cell biology supporting CO ₂ assimilation in diverse organisms.