Dissimilatory nitrate reduction to ammonium driven by different electron donors: Mechanisms, recent advances, and future perspectives

Dissimilatory nitrate reduction to ammonium (DNRA) is a critical process in the global nitrogen cycle, transforming nitrate into ammonium. Various substances have been identified that can serve as electron donors in the DNRA process, including organic carbon, sulfides, methane, ferrous iron (Fe(II)), electrons produced by electrodes in bioelectrochemical systems and photoelectrons. Understanding these microbially mediated DNRA processes is essential for understanding nitrate reduction and maintaining the ecological nitrogen balance. This review summarizes the recent advances in metabolic pathways and key functional microorganisms involved in different electron-donor-driven DNRA processes. Furthermore, it explores the potential applications of DNRA for nitrogen retention, wastewater treatment and ammonia recovery. In addition, the review highlights the importance of DNRA in the nitrogen cycle and global ecosystems, while providing new insights into the optimization of DNRA applications.