Journey of the swift nitrogen transformation: Unveiling comammox from discovery to deep understanding.

COMplete AMMonia OXidizer (comammox) refers to microorganisms that have the function of oxidizing NH 4 + to NO 3 − alone. The discovery of comammox overturned the two-step theory of nitrification in the past century and triggered many important scientific questions about the nitrogen cycle in nature. This comprehensive review delves into the origin and discovery of comammox, providing a detailed account of its detection primers, clades metabolic variations, and environmental factors. An in-depth analysis of the ecological niche differentiation among ammonia oxidizers was also discussed. The intricate role of comammox in anammox systems and the relationship between comammox and nitrogen compound emissions are also discussed. Finally, the relationship between comammox and anammox is displayed, and the future research direction of comammox is prospected. This review reveals the metabolic characteristics and distribution patterns of comammox in ecosystems, providing new perspectives for understanding nitrogen cycling and microbial ecology. Additionally, it offers insights into the potential application value and prospects of comammox. [Display omitted] • Unraveling the mysteries of comammox: from discovery to ecological significance. • The environmental factors and influencing mechanisms were summarized. • Comammox thriving mostly in freshwater ecosystems. • Is comammox a green engineering process worth further evaluation. • Future focus: evaluating actual contribution and conducting engineering application. [ABSTRACT FROM AUTHOR]