Nonliving respiration: Another breath in the soil?

The present study challenges the traditional view that the respiration of organic carbon to CO2 is an exclusively intracellular process, revealing that organic compound respiration can occur spontaneously in an extracellular context in soils. Using 1H nuclear magnetic resonance spectroscopy to analyze the dynamics of the sterile soil exometabolomes alongside C-CO2 flux analyses and sterile soil fuel cells, we show that soil catalysts facilitate a diverse array of substrate-driven reactions, leading to the complete oxidation of organic compounds to CO2 with O2 consumption. Our results indicate that soil particles are capable of transferring electrons from substrates to the final acceptor, thereby sustaining metabolism-like processes independently of living cells. Notably, some soil catalysts and induced respiration remain stable for more than 6 years. These findings support the coexistence of cellular and noncellular metabolic pathways in soil respiration.