Bradyrhizobium japonicum is a Gram-negative soil bacterium symbiotically associated with soya bean plants, which is also able to denitrify under free-living and symbiotic conditions. In B. japonicum, the napEDABC, nirK, norCBQD and nosRZDYFLX genes which encode reductases for nitrate, nitrite, nitric oxide and nitrous oxide respectively are required for denitrification. Similar to many other denitrifiers, expression of denitrification genes in B. japonicum requires both oxygen limitation and the presence of nitrate or a derived nitrogen oxide. In B. japonicum, a sophisticated regulatory network consisting of two linked regulatory cascades co-ordinates the expression of genes required for microaerobic respiration (the FixLJ/FixK2 cascade) and for nitrogen fixation (the RegSR/NifA cascade). The involvement of the FixLJ/FixK2 regulatory cascade in the microaerobic induction of the denitrification genes is well established. In addition, the FNR (fumarase and nitrate reduction regulator)/CRP(cAMP receptor protein)-type regulator NnrR expands the FixLJ/FixK2 regulatory cascade by an additional control level. A role for NifA is suggested in this process by recent experiments which have shown that it is required for full expression of denitrification genes in B. japonicum. The present review summarizes the current understanding of the regulatory network of denitrification in B. japonicum.
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February 2011
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Conference Article|
January 19 2011
Emerging complexity in the denitrification regulatory network of Bradyrhizobium japonicum
María J. Torres;
María J. Torres
1Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, P.O. Box 419, 18080 Granada, Spain
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Emilio Bueno;
Emilio Bueno
1Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, P.O. Box 419, 18080 Granada, Spain
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Socorro Mesa;
Socorro Mesa
1Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, P.O. Box 419, 18080 Granada, Spain
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Eulogio J. Bedmar;
Eulogio J. Bedmar
1Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, P.O. Box 419, 18080 Granada, Spain
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María J. Delgado
María J. Delgado
1
1Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, P.O. Box 419, 18080 Granada, Spain
1To whom correspondence should be addressed (email mdelgado@eez.csic.es).
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Publisher: Portland Press Ltd
Received:
September 27 2010
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© The Authors Journal compilation © 2011 Biochemical Society
2011
Biochem Soc Trans (2011) 39 (1): 284–288.
Article history
Received:
September 27 2010
Citation
María J. Torres, Emilio Bueno, Socorro Mesa, Eulogio J. Bedmar, María J. Delgado; Emerging complexity in the denitrification regulatory network of Bradyrhizobium japonicum. Biochem Soc Trans 1 February 2011; 39 (1): 284–288. doi: https://doi.org/10.1042/BST0390284
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