Dinitrogen production modes of diverse anammox bacteria and the contribution in nitrogen cycle: A review

Abstract

Anaerobic ammonia oxidation (anammox) bacteria are lithoautotrophs coupling the oxidation of ammonium with the reduction of nitrite to produce dinitrogen (N₂). Anammox reaction is one of the important ones in inorganic nitrogen removal. Here, the reported anammox bacteria, nitrogen metabolism, dinitrogen production modes coupled with other microorganisms, occurrence and contribution in diverse ecosystems were comprehensively summarized. A total of 36 species affiliated to 7 genera of anammox bacteria have been reported. Anammox bacteria use nitrite and nitric oxide as electron acceptors and ammonium as electron donor to carry out anammox reaction. Some also have functional genes required for Dissimilatory nitrate reduction to ammonium (DNRA) process. Anammox bacteria can conduct nitrogen removal via coupling with multiple microorganisms, and realized nitrogen removal via coupling with iron reduction, sulfate reduction, heterotrophic denitrification, sulfur autotrophic denitrification, partial nitrification, denitrifying anaerobic methane oxidation. However, the mechanisms and construction of efficient symbiotic systems consisting of anammox bacteria and other microorganisms is still unclear. Anammox is widespread in ecosystems, and contributes considerable nitrogen yield. Quantification of the nitrogen loss contributed by anammox bacteria in typical ecosystems is an issue in future. Collectively, bacteria have diverse carbon and nitrogen metabolic pathways, and can remove reactive nitrogen species via coupling with other microorganisms, showing a complex and critical robust roles in nitrogen transformation in diverse ecosystems.