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Journal of Bacteriology, February 2009, p. 996-1005, Vol. 191, No. 3
0021-9193/09/$08.00+0     doi:10.1128/JB.00873-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Catabolite Repression Control of napF (Periplasmic Nitrate Reductase) Operon Expression in Escherichia coli K-12{triangledown}

Valley Stewart,* Peggy J. Bledsoe,{dagger} Li-Ling Chen, and Amie Cai{ddagger}

Department of Microbiology, University of California, Davis, California 95616-8665

Received 25 June 2008/ Accepted 13 November 2008

Escherichia coli, a facultative aerobe, expresses two distinct respiratory nitrate reductases. The periplasmic NapABC enzyme likely functions during growth in nitrate-limited environments, whereas the membrane-bound NarGHI enzyme functions during growth in nitrate-rich environments. Maximal expression of the napFDAGHBC operon encoding periplasmic nitrate reductase results from synergistic transcription activation by the Fnr and phospho-NarP proteins, acting in response to anaerobiosis and nitrate or nitrite, respectively. Here, we report that, during anaerobic growth with no added nitrate, less-preferred carbon sources stimulated napF operon expression by as much as fourfold relative to glucose. Deletion analysis identified a cyclic AMP receptor protein (Crp) binding site upstream of the NarP and Fnr sites as being required for this stimulation. The napD and nrfA operon control regions from Shewanella spp. also have apparent Crp and Fnr sites, and expression from the Shewanella oneidensis nrfA control region cloned in E. coli was subject to catabolite repression. In contrast, the carbon source had relatively little effect on expression of the narGHJI operon encoding membrane-bound nitrate reductase under any growth condition tested. Carbon source oxidation state had no influence on synthesis of either nitrate reductase. The results suggest that the Fnr and Crp proteins may act synergistically to enhance NapABC synthesis during growth with poor carbon sources to help obtain energy from low levels of nitrate.

* Corresponding author. Mailing address: Department of Microbiology, University of California, One Shields Avenue, Davis, CA 95616-8665. Phone: (530) 754-7994. Fax: (530) 752-9014. E-mail: vjstewart{at}ucdavis.edu

{triangledown} Published ahead of print on 5 December 2008.

{dagger} Present address: Department of Neurobiology, Duke University School of Medicine, Durham, NC 27705.

{ddagger} Permanent address: Mira Loma High School, Sacramento, CA 95821.

Journal of Bacteriology, February 2009, p. 996-1005, Vol. 191, No. 3
0021-9193/09/$08.00+0     doi:10.1128/JB.00873-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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