This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supplemental material
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Itakura, M.
Right arrow Articles by Minamisawa, K.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Itakura, M.
Right arrow Articles by Minamisawa, K.
Agricola
Right arrow Articles by Itakura, M.
Right arrow Articles by Minamisawa, K.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, December 2008, p. 7258-7264, Vol. 74, No. 23
0099-2240/08/$08.00+0     doi:10.1128/AEM.01850-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Generation of Bradyrhizobium japonicum Mutants with Increased N2O Reductase Activity by Selection after Introduction of a Mutated dnaQ Gene {triangledown} ,{dagger}

Manabu Itakura,1 Kazufumi Tabata,2 Shima Eda,1 Hisayuki Mitsui,1 Kiriko Murakami,2 Junichi Yasuda,2 and Kiwamu Minamisawa1*

Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai, Miyagi, Japan,1 Neo-Morgan Laboratory, Incorporated, Biotechnology Research Center, Nogawa, Miyamae-ku, Kanagawa 216-0001, Japan2

Received 10 August 2008/ Accepted 7 October 2008

We obtained two beneficial mutants of Bradyrhizobium japonicum USDA110 with increased nitrous oxide (N2O) reductase (N2OR) activity by introducing a plasmid containing a mutated B. japonicum dnaQ gene (pKQ2) and performing enrichment culture under selection pressure for N2O respiration. Mutation of dnaQ, which encodes the epsilon subunit of DNA polymerase III, gives a strong mutator phenotype in Escherichia coli. pKQ2 introduction into B. japonicum USDA110 increased the frequency of occurrence of colonies spontaneously resistant to kanamycin. A series of repeated cultivations of USDA110 with and without pKQ2 was conducted in anaerobic conditions under 5% (vol/vol) or 20% (vol/vol) N2O atmosphere. At the 10th cultivation cycle, cell populations of USDA110(pKQ2) showed higher N2OR activity than the wild-type strains. Four bacterial mutants lacking pKQ2 obtained by plant passage showed 7 to 12 times the N2OR activity of the wild-type USDA110. Although two mutants had a weak or null fix phenotype for symbiotic nitrogen fixation, the remaining two (5M09 and 5M14) had the same symbiotic nitrogen fixation ability and heterotrophic growth in culture as wild-type USDA110.

* Corresponding author. Mailing address: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan. Phone and fax: 81-22-217-5684. E-mail: kiwamu{at}ige.tohoku.ac.jp

{triangledown} Published ahead of print on 10 October 2008.

{dagger} Supplemental material for this article may be found at http://aem.asm.org/.

Applied and Environmental Microbiology, December 2008, p. 7258-7264, Vol. 74, No. 23
0099-2240/08/$08.00+0     doi:10.1128/AEM.01850-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»