Decoupled respiration in electro-active bacteria.

Studies on electron-transfer pathways in certain bacterial strains have revealed that the degree of coupling of electron transfer to proton translocation along the respiratory chain can be regulated according to metabolic demands. This first line of metabolic response, based on the existence of energy dissipation mechanisms, has not been demonstrated to be a general pattern across the bacterial kingdom, let alone to be operative in electro-active bacteria. In this study, we hypothesized that electro-active cells should respond to over-polarization by also triggering energy decoupling mechanisms to prevent metabolic overloads. Based on electrochemical analyses, we propose that the recently discovered inner-membrane cytochrome CbcBA - used by electro-active Geobacter sulfurreducens bacteria for cellular respiration near the thermodynamic energetic limit - can also act as an energy dissipation gate when the metabolism is demanded, contributing to regulate the energy balance of the cell by decoupling carbon assimilation from electrode respiration.