Bao, J.; Somvanshi, T.; Tian, Y.; Laird, M.; Garcia, P. S.; Schoene, C.; Rother, M.; Borrel, G.; Scheller, S.

Methanogens are essential players in the global carbon cycle. Methanosarcinales possess one of the most diverse metabolic repertoires for methanogenesis, but they have never been observed to utilize formate as a substrate. We successfully reprogrammed the primary metabolism of Methanosarcina acetivorans by introducing an exogenous formate dehydrogenase derived from a closely related species. The engineered strains acquired the capacity to harness energy from formate-dependent methanogenesis pathways, including formate-dependent methyl reduction and formate-dependent carbon dioxide reduction. The ability of M. acetivorans to thrive on formate suggests the existence of essential accessory machinery and metabolic redundancy for generating reduced ferredoxins from F420H2. This remarkable plasticity in energy metabolism raises the possibility that an ancestral lineage of Methanosarcinales may have possessed the capacity to utilize formate. By combining this genetically modified strain with a disruption in methyl disproportionation, we have created a novel tool for investigating and manipulating the components of the F420 reduction and methanogenesis pathways independently.