Dissimilatory nitrate reduction to ammonium has a competitive advantage over denitrification under nitrate-limited conditions

Abstract

Dissimilatory nitrate reduction to ammonium (DNRA) is important for nitrogen retention in ecosystems and is in competition with denitrification. However, denitrification tends to dominate. A high organic carbon content and limited nitrate are the key conditions for DNRA to outcompete denitrification, but the mechanisms for controlling the nitrate fate are not well understood. This review systematically summarizes the processes of and correlation between DNRA and denitrification, with a focus on outlining the characteristics of the active enzymes, including the enzyme structure, substrate affinity, and electron transfer. The competitive advantage of DNRA for electron acceptors are highlighted and discussed from enzymatic and kinetic perspectives. The high electron acquisition of DNRA causes it to dominate nitrate removal under nitrate limitation. Finally, strategies for promoting environmental nitrogen retention through DNRA are proposed, and possible directions for future research are suggested. This review aims to improve understanding of the competitive mechanisms of DNRA and denitrification and to promote the application and development of DNRA as a sustainable nitrogen retention strategy.