# The functional analysis of NirBD in microorganisms and the efficacies of NirBD on the soil nitrogen storage and N2O emission

## TL;DR

This paper reviews the role of the NirBD enzyme in the nitrogen cycle, focusing on its impact on soil nitrogen storage and nitrous oxide emissions.

## Contribution

The paper provides a comprehensive review of NirBD's functional roles and expression mechanisms across different microorganisms.

## Key findings

- NirBD regulates N2O release through assimilatory and dissimilatory pathways.
- The review clarifies factors affecting NirBD expression in microorganisms.
- NirBD's role in nitrogen retention and N2O emission is discussed under different environmental conditions.

## Abstract

The siroheme-containing nitrite reductase (NirBD), which is encoded by the nirBD gene, is a functional enzyme in the nitrogen cycle. The NirBD enzyme can regulate N2O release through the two distinct pathways of assimilatory nitrate/nitrite reduction to biomass and dissimilatory nitrate/nitrite reduction to ammonium. Therefore, a thorough comprehension of the function of NirBD in microorganisms can enable us to better understanding the contributions for nitrogen retention and N2O emission. However, the knowledge of the functions and expression mechanisms of nirBD gene across different microorganisms remains limited. This review synthesized the current research on the phylogenetic distribution and catalytic versatility of NirBD in fungi, bacteria, and actinomycetes. The contributions of NirBD for nitrogen retention and N2O emission were extensively discussed under anaerobic and aerobic conditions. The expression mechanism of NirBD was demonstrated. The factors that affect the expression amount of the NirBD enzyme in microorganisms were clarified systematically. This review not only elucidated the unique role of NirBD in the nitrogen metabolism but also provided a critical theoretical foundation for developing future strategies to enhance soil nitrogen fertility and mitigate N2O emissions.

Image 1