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学術研究成果リスト

Detail of Grant Awarded Academic Researches

Project

Investigation of ecology and role in nitrogen dynamics of nitrous oxide producing bacteria in river Tamagawa

Academic
Research
No.296
Principal
Investigator
Mitsunori Tarao
Affiliation Tokyo University of Agriculture and Technology, Faculty of Agriculture
Research
Summary

This study aimed to investigate distribution of nitrous oxide producing denitrifiers in river water and biofilm attached on stone at upstream, midstream, and downstream of river Tamagawa, and to consider their involvement in nitrous oxide (N2O) emission from the river. Using a medium with lower concentration of organic carbon and NO3--N (70 and 7 mg L–1, respectively), the number of total denitrifiers detected was up to 1,000-fold higher than using a nitrate broth with higher concentration of organic carbon and NO3N (3,900 and 70 mg L-1, respecrively). A large part of total denitrifiers appeared to consist of nitrous oxide producing denitrifier. A bacterial strain of nitrous oxide producing denitrifier, strain MS-1, was isolated, and it reduced most of all nitrate to nitrite and did a half of nitrate to N2O. When river water and a stone with biofilm, which were collected from upstream or downstream, were incubated in a sealed bottle, gaseous nitrogen emitted from samples of upstream consisted of N2, although that emitted from samples of downstream consisted of N2O. The possibility that nitrous oxide producing denitrifier involves in N2O emission from river Tamagawa was suggested.


This study suggested that most of all total denitrifiers appear to consist of nitrous oxide producing denitrifiers in river Tamagawa, and possibility that nitrous oxide producing denitrifier involves in N2O emission from the river. Future studies are needed to understand the dynamics of nitrous oxide producing denitrifiers, nitrous oxide reducing denitrifier, and nitrifier, andtheir involvement in N2O emission from the river. This study also succeeded in isolation of a bacterial strain of nitrous oxide producing denitrifier, strain MS-1. Nitrous oxide producing denitrifiers whose denitrification characteristics are similar with strain MS-1 may be present in not only river Tamagawa but also other aquatic environments. Qualitative and quantitative studies of involvement of such denitrifiers in N2O emission and nitrogen cycle in river are also needed.

Collaborators
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