This Article
Right arrow Full Text
Right arrow Full Text (PDF)
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 HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Wang, H.
Right arrow Articles by Gunsalus, R. P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Wang, H.
Right arrow Articles by Gunsalus, R. P.

 Previous Article  |  Next Article 

Journal of Bacteriology, October 2000, p. 5813-5822, Vol. 182, No. 20
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

The nrfA and nirB Nitrite Reductase Operons in Escherichia coli Are Expressed Differently in Response to Nitrate than to Nitrite

Henian Wang and Robert P. Gunsalus*

Department of Microbiology and Molecular Genetics, University of California, Los Angeles, California 90095-1489

Received 10 March 2000/Accepted 27 July 2000

Escherichia coli possesses two distinct nitrite reductase enzymes encoded by the nrfA and nirB operons. The expression of each operon is induced during anaerobic cell growth conditions and is further modulated by the presence of either nitrite or nitrate in the cells' environment. To examine how each operon is expressed at low, intermediate, and high levels of either nitrate or nitrite, anaerobic chemostat culture techniques were employed using nrfA-lacZ and nirB-lacZ reporter fusions. Steady-state gene expression studies revealed a differential pattern of nitrite reductase gene expression where optimal nrfA-lacZ expression occurred only at low to intermediate levels of nitrate and where nirB-lacZ expression was induced only by high nitrate conditions. Under these conditions, the presence of high levels of nitrate suppressed nrfA gene expression. While either NarL or NarP was able to induce nrfA-lacZ expression in response to low levels of nitrate, only NarL could repress at high nitrate levels. The different expression profile for the alternative nitrite reductase operon encoded by nirBDC under high-nitrate conditions was due to transcriptional activation by either NarL or NarP. Neither response regulator could repress nirB expression. Nitrite was also an inducer of nirB and nrfA gene expression, but nitrate was always the more potent inducer by >100-fold. Lastly, since nrfA operon expression is only induced under low-nitrate concentrations, the NrfA enzyme is predicted to have a physiological role only where nitrate (or nitrite) is limiting in the cell environment. In contrast, the nirB nitrite reductase is optimally synthesized only when nitrate or nitrite is in excess of the cell's capacity to consume it. Revised regulatory schemes are presented for NarL and NarP in control of the two operons.

* Corresponding author. Mailing address: Department of Microbiology and Molecular Genetics, University of California, Los Angeles, CA 90095-1489. Phone: (310) 206-8201. Fax: (310) 206-5231. E-mail: robg{at}microbiol.ucla.edu.

Journal of Bacteriology, October 2000, p. 5813-5822, Vol. 182, No. 20
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:

  • Desai, T. A., Rodionov, D. A., Gelfand, M. S., Alm, E. J., Rao, C. V. (2009). Engineering transcription factors with novel DNA-binding specificity using comparative genomics. Nucleic Acids Res 37: 2493-2503 [Abstract] [Full Text]  
  • Weiss, B. (2006). Evidence for Mutagenesis by Nitric Oxide during Nitrate Metabolism in Escherichia coli. J. Bacteriol. 188: 829-833 [Abstract] [Full Text]  
  • Goh, E.-B., Bledsoe, P. J., Chen, L.-L., Gyaneshwar, P., Stewart, V., Igo, M. M. (2005). Hierarchical Control of Anaerobic Gene Expression in Escherichia coli K-12: the Nitrate-Responsive NarX-NarL Regulatory System Represses Synthesis of the Fumarate-Responsive DcuS-DcuR Regulatory System. J. Bacteriol. 187: 4890-4899 [Abstract] [Full Text]  
  • Haveman, S. A., Greene, E. A., Stilwell, C. P., Voordouw, J. K., Voordouw, G. (2004). Physiological and Gene Expression Analysis of Inhibition of Desulfovibrio vulgaris Hildenborough by Nitrite. J. Bacteriol. 186: 7944-7950 [Abstract] [Full Text]  
  • Wang, H., Gunsalus, R. P. (2003). Coordinate Regulation of the Escherichia coli Formate Dehydrogenase fdnGHI and fdhF Genes in Response to Nitrate, Nitrite, and Formate: Roles for NarL and NarP. J. Bacteriol. 185: 5076-5085 [Abstract] [Full Text]  
  • Corker, H., Poole, R. K. (2003). Nitric Oxide Formation by Escherichia coli: DEPENDENCE ON NITRITE REDUCTASE, THE NO-SENSING REGULATOR Fnr, AND FLAVOHEMOGLOBIN Hmp. J. Biol. Chem. 278: 31584-31592 [Abstract] [Full Text]  
  • Stewart, V., Bledsoe, P. J. (2003). Synthetic lac Operator Substitutions for Studying the Nitrate- and Nitrite-Responsive NarX-NarL and NarQ-NarP Two-Component Regulatory Systems of Escherichia coli K-12. J. Bacteriol. 185: 2104-2111 [Abstract] [Full Text]  
  • Stewart, V., Lu, Y., Darwin, A. J. (2002). Periplasmic Nitrate Reductase (NapABC Enzyme) Supports Anaerobic Respiration by Escherichia coli K-12. J. Bacteriol. 184: 1314-1323 [Abstract] [Full Text]  


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