2023 Fiscal Year Final Research Report

Elucidate the missing link of terrestrial nitrogen cycle – Who is the key nitrifier in acidic soil?

Research Project

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Project/Area Number	19H01156
Research Category	Grant-in-Aid for Scientific Research (A)
Allocation Type	Single-year Grants
Section	一般
Review Section	Medium-sized Section 63:Environmental analyses and evaluation and related fields
Research Institution	National Agriculture and Food Research Organization
Principal Investigator	Tago Kanako 国立研究開発法人農業・食品産業技術総合研究機構, 農業環境研究部門, 上級研究員 (20432198)
Co-Investigator(Kenkyū-buntansha)	早津雅仁国立研究開発法人農業・食品産業技術総合研究機構, 農業環境研究部門, 再雇用職員 (70283348) 諏訪裕一中央大学, 理工学部, 教授 (90154632) 藤谷拓嗣中央大学, 理工学部, 助教 (50708617)
Project Period (FY)	2019-04-01 – 2023-03-31
Keywords	窒素循環 / 硝化菌 / アンモニア酸化菌 / 亜硝酸酸化菌
Outline of Final Research Achievements	To elucidate the mechanism of nitrification in acidic soils, we investigated characteristics of nitrogen metabolism of acid-tolerant nitrifying microbial community and key nitrifying bacteria. Isolation of a novel acid-tolerant ammonia-oxidizing bacteria was successfully achieved. Neutral-type nitrite-oxidizing bacteria that functions in the acid-tolerant nitrifying community was cultured in pure, and it was shown that even neutral nitrite-oxidizing bacteria can function in an acidic environment. Genetic information involved in nitrogen metabolism such as denitrification of heterotrophic bacteria was examined by metagenomic analysis. It is assumed that a heterotrophic bacterial community is formed by utilizing polysaccharides produced by the nitrifying bacteria, and that a complex nitrogen metabolic pathway is formed in the community. Based on these results, it was deduced that nitrification and denitrification proceed simultaneously and stably even under acidic conditions.
Free Research Field	土壌微生物
Academic Significance and Societal Importance of the Research Achievements	これまで知られている酸性土壌環境に適応したアンモニア酸化細菌は1種のみであったが、本研究において新属と推定される新規なアンモニア酸化細菌の分離と特徴づけに成功した。さらに酸性環境でも中性型の亜硝酸酸化細菌が微生物コミュニティー中で機能することを明らかにした。これらの知見は酸性土壌における窒素循環や一酸化二窒素の生成機構の理解に貢献する。さらに酸性土壌の硝化制御技術（例えば硝化抑制剤の設計や窒素肥料施用法の改善技術）の開発に役立てることができる。