Nitrate respiration by the N2-fixing symbiotic bacteria Bradyrhizobium japonicum USDA110 is mediated by a Nap (periplasmic nitrate reductase) encoded by the napEDABC genes. Expression of a transcriptional fusion of the nap promoter region to the reporter gene lacZ, PnapE-lacZ, was very low in aerobically grown cells of USDA110, but expression was induced approx. 3-fold when the cells were cultured under microaerobic conditions, and 12-fold when nitrate was added to the microaerobic incubation medium. The PnapE-lacZ fusion was not expressed in the fixL 7403, fixJ 7360 and fixK2 9043 mutant strains. Microaerobic induction of the PnapE-lacZ fusion was retained in the nnrR 8678 mutant, but no increase in β-galactosidase activity was observed upon nitrate addition. Western-blot and Methyl Viologen-dependent nitrate reductase activity assays showed that synthesis and activity of the catalytic NapA subunit in USDA110 was similar to that in the napC 0906 and nirK GRK308 mutant strains incubated microaerobically with nitrate. These results suggest that nitrate and nitrite, which are not reduced by the napC 0906 and nirK GRK308 mutant cells respectively, induced the synthesis and activity of NapA; conversely, formation of endogenous NO was not required for induction of Nap expression.
Skip Nav Destination
Article navigation
February 2006
-
Cover Image
Cover Image
- PDF Icon PDF LinkFront Matter
- PDF Icon PDF LinkTable of Contents
Conference Article|
January 20 2006
The Bradyrhizobium japonicum napEDABC genes are controlled by the FixLJ-FixK2-NnrR regulatory cascade
E.F. Robles;
E.F. Robles
1Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, P.O. Box 419, 18080 Granada, Spain
Search for other works by this author on:
C. Sánchez;
C. Sánchez
1Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, P.O. Box 419, 18080 Granada, Spain
Search for other works by this author on:
N. Bonnard;
N. Bonnard
1Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, P.O. Box 419, 18080 Granada, Spain
Search for other works by this author on:
M.J. Delgado;
M.J. Delgado
1Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, P.O. Box 419, 18080 Granada, Spain
Search for other works by this author on:
E.J. Bedmar
E.J. Bedmar
1
1Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, P.O. Box 419, 18080 Granada, Spain
1 To whom correspondence should be addressed (email ejbedmar@eez.csic.es).
Search for other works by this author on:
Publisher: Portland Press Ltd
Received:
September 22 2005
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© 2006 The Biochemical Society
2006
Biochem Soc Trans (2006) 34 (1): 108–110.
Article history
Received:
September 22 2005
Citation
E.F. Robles, C. Sánchez, N. Bonnard, M.J. Delgado, E.J. Bedmar; The Bradyrhizobium japonicum napEDABC genes are controlled by the FixLJ-FixK2-NnrR regulatory cascade. Biochem Soc Trans 1 February 2006; 34 (1): 108–110. doi: https://doi.org/10.1042/BST0340108
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Captcha Validation Error. Please try again.