記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.5194/acp-25-11895-2025

Web of Science

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.aca.2025.344368

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掲載種別：研究論文（学術雑誌）   出版者・発行元：American Society for Microbiology  

ABSTRACT

Dissimilatory nitrate reduction to ammonium (DNRA), driven by nitrate-ammonifying bacteria, is an increasingly appreciated nitrogen-cycling pathway in terrestrial ecosystems. This process reportedly generates nitrous oxide (N ₂ O), a strong greenhouse gas with ozone-depleting effects. However, it remains poorly understood how N ₂ O is produced by environmental nitrate-ammonifiers and how to identify DNRA-derived N ₂ O. In this study, we characterize two novel enzymatic pathways responsible for N ₂ O production in Geobacteraceae strains, which are predominant nitrate-ammonifying bacteria in paddy soils. The first pathway involves a membrane-bound nitrate reductase (Nar) and a hybrid cluster protein complex (Hcp–Hcr) that catalyzes the conversion of NO ₂ ⁻ to NO and subsequently to N ₂ O. The second pathway is observed in Nar-deficient bacteria, where the nitrite reductase (NrfA) generates NO, which is then reduced to N ₂ O by Hcp–Hcr. These enzyme combinations are prevalent across the domain Bacteria. Moreover, we observe distinctive isotopocule signatures of DNRA-derived N ₂ O from other established N ₂ O production pathways, especially through the highest ¹⁵ N-site preference (SP) values (43.0‰–49.9‰) reported so far, indicating a robust means for N ₂ O source partitioning. Our findings demonstrate two novel N ₂ O production pathways in DNRA that can be isotopically distinguished from other pathways.

IMPORTANCE

Stimulation of DNRA is a promising strategy to improve fertilizer efficiency and reduce N ₂ O emission in agriculture soils. This process converts water-leachable NO ₃ ⁻ and NO ₂ ⁻ into soil-adsorbable NH ₄ ⁺ , thereby alleviating nitrogen loss and N ₂ O emission resulting from denitrification. However, several studies have noted that DNRA can also be a source of N ₂ O, contributing to global warming. This contribution is often masked by other N ₂ O generation processes, leading to a limited understanding of DNRA as an N ₂ O source. Our study reveals two widespread yet overlooked N ₂ O production pathways in Geobacteraceae , the predominant DNRA bacteria in paddy soils, along with their distinctive isotopocule signatures. These findings offer novel insights into the role of the DNRA bacteria in N ₂ O production and underscore the significance of N ₂ O isotopocule signatures in microbial N ₂ O source tracking.

DOI： 10.1128/mbio.02540-24

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DOI： 10.21203/rs.3.rs-4789103/v1

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.soilbio.2024.109358

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総ページ数：iv, 153p   記述言語：日本語  

CiNii Books

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開催年月日： 2025年11月

記述言語：英語   会議種別：ポスター発表  

開催地：福岡   国名：日本国  

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開催年月日： 2025年11月

記述言語：日本語   会議種別：ポスター発表  

開催地：福岡   国名：日本国  

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開催年月日： 2025年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：相模原   国名：日本国  

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開催年月日： 2025年10月

記述言語：日本語   会議種別：ポスター発表  

開催地：柏   国名：日本国  

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開催年月日： 2025年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：名古屋   国名：日本国  

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