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Applied and Environmental Microbiology, April 2006, p. 2526-2532, Vol. 72, No. 4
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.4.2526-2532.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Symbiotic Bradyrhizobium japonicum Reduces N2O Surrounding the Soybean Root System via Nitrous Oxide Reductase

Reiko Sameshima-Saito,{dagger} Kaori Chiba, Junta Hirayama, Manabu Itakura, Hisayuki Mitsui, Shima Eda, and Kiwamu Minamisawa*

Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan

Received 23 October 2005/ Accepted 25 January 2006

N2O reductase activity in soybean nodules formed with Bradyrhizobium japonicum was evaluated from N2O uptake and conversion of 15N-N2O into 15N-N2. Free-living cells of USDA110 showed N2O reductase activity, whereas a nosZ mutant did not. Complementation of the nosZ mutant with two cosmids containing the nosRZDFYLX genes of B. japonicum USDA110 restored the N2O reductase activity. When detached soybean nodules formed with USDA110 were fed with 15N-N2O, they rapidly emitted 15N-N2 outside the nodules at a ratio of 98.5% of 15N-N2O uptake, but nodules inoculated with the nosZ mutant did not. Surprisingly, N2O uptake by soybean roots nodulated with USDA110 was observed even in ambient air containing a low concentration of N2O (0.34 ppm). These results indicate that the conversion of N2O to N2 depends exclusively on the respiratory N2O reductase and that soybean roots nodulated with B. japonicum carrying the nos genes are able to remove very low concentrations of N2O.

* Corresponding author. Mailing address: Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan. Phone and fax: 81-22-217-5684. E-mail: kiwamu{at}ige.tohoku.ac.jp.

{dagger} Present address: Environmental Science for Human Life, Faculty of Agriculture, Shizuoka University, Ohya 836, Shizuoka 422-8529, Japan.

Applied and Environmental Microbiology, April 2006, p. 2526-2532, Vol. 72, No. 4
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.4.2526-2532.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Itakura, M., Tabata, K., Eda, S., Mitsui, H., Murakami, K., Yasuda, J., Minamisawa, K. (2008). Generation of Bradyrhizobium japonicum Mutants with Increased N2O Reductase Activity by Selection after Introduction of a Mutated dnaQ Gene. Appl. Environ. Microbiol. 74: 7258-7264 [Abstract] [Full Text]  


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