Extracellular electron transfer powers flavinylated extracellular reductases in Gram-positive bacteria

Significance Strategies of energy metabolism are variable across the microbial world and fundamentally reflect distinct ecological dynamics. The complex electron transfer mechanisms that support many such processes take place in the cell membrane but can be wired to the exterior of the cell in some circumstances. The results presented here reveal a family of extracellular reductases that possess a post-translationally flavinylated sequence motif. This motif provides a conserved framework that mediates electron transfer from the membrane to different extracellular small molecules. These findings advance our understanding of microbial energy metabolism and identify a generalized and modular electron transfer strategy that could be exploited for applications in metabolic engineering.