(191bj) Efficient Energy Utilization in Carbon-Fixing Moorella Thermoacetica

Carbon dioxide is the main greenhouse gas that is produced in combustion and cellular respiration. On the other side of the carbon cycle, plants and algae reduce CO₂ using photosynthesis. Despite technological advances, industrial society emits CO₂ faster than the rate at which it can be eliminated, breaking balance in the carbon cycle. Metabolic CO₂ reduction requires energy in two forms: reducing power and ATP. Here we find that when glucose is the sole energy source, non-photosynthetic carbon-fixing anaerobe Moorella thermoacetica is limited by reducing power. Despite electron-limitation, we observe near-complete carbon utilization for acetate and biomass production. Using ¹³C glucose and ¹²CO₂, we observe that CO₂ accounts for most carbons of non-aromatic amino acids and secreted acetate. In this talk, we will introduce and apply simultaneous ¹³C and ¹⁸O tracing to identify energy-efficient pathways that allow cells to proliferate in chronically nutrient- and energy-limited environments. Identification of metabolic limitations using similar isotope tracer strategies should be broadly useful for improving bioprocesses.