N2O could be a potential electron acceptor for anaerobic ammonium oxidation.
This perspective will expand our understanding of transformation process in N cycle.
Anaerobic ammonium (NH 4 + ) oxidation is one of the key processes in nitrogen cycling. After the canonical pathway for it using NO 2 − as the electron acceptor was first discovered, novel pathways for it using Fe3+, Mn4+, SO 4 2− , or AsO 4 3− , as electron acceptors have recently been confirmed. Nitrous oxide (N2O) is a strong oxidant, and there is currently no report on whether it can act as an electron acceptor to couple with anaerobic ammonium oxidation in natural habitats. From a thermodynamic perspective, the potential anaerobic ammonium oxidation driven by N2O reduction generates much higher free energy than the canonical anaerobic ammonium oxidation driven by NO 2 − reduction, indicating that it is more likely to occur spontaneously. Some specific habitats such as ammonium-rich wastewater, with low levels of active organic carbon and high concentration of N2O may be favorable for N2O-mediated anaerobic ammonium oxidation. The extracellular electron transfer between symbiotic bacteria may be an important way of electron transfer in this coupling process. By using enrichment culture combined with 15N labeling technique, oxidation rate, electron transfer pathway, and metagenome (and transcriptome) information of this coupling process could be powerfully investigated. The study could expanding our understanding of transformation process in nitrogen biogeochemical cycle.
