The hidden source of N2O production-the denitrifying bacteria functioning in plants

2019 Fiscal Year Final Research Report

• Project/Area Number: 16H05059
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Environmental agriculture(including landscape science)
• Research Institution: National Agriculture and Food Research Organization
• Principal Investigator: Kanako Tago 国立研究開発法人農業・食品産業技術総合研究機構, 農業環境変動研究センター, 主任研究員 (20432198)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 好気的脱窒

Outline of Final Research Achievements

We had found that nitrous oxide is emitted from not only soil but also unharvested crop residues on a cabbage field, and hypothesized that denitrification occurs in the crop residue. As a result, some plant indigenous bacteria were isolated as denitrifiers from the crop residue, and the isolates showed denitrification activity under an aerobic (static) condition. Genomic features were not identical among the isolates: some of the isolates encoded nitrous oxide reductase gene on their genomes while the others didn't. A high amount of nitrate was detected in the residue. Culturing experiments with the residue showed cell growth of the isolate was observed with a reduction of nitrate concomitant with a release of nitrous oxide. Moreover, some sugars and organic acids contained in the residue were shown to be electron donors for the denitrifiers. These results suggest that some plant indigenous bacteria can utilize components of the crop residue to denitrify and produce nitrous oxide.

Free Research Field

環境微生物学

Academic Significance and Societal Importance of the Research Achievements

以前から作物残さのN2O発生への関与は認められていたが、ほとんどが土壌微生物によるものと考えられていた。本研究課題で明らかにした作物体から直接発生する一酸化二窒素（N2O）の発生メカニズムに関する研究成果は、これまで詳細が不明であった作物（植物）という新たなN2O発生源とそこに存在する植物に常在する微生物の窒素循環への関与という新たな知見を提案する。