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J. Biol. Chem., Vol. 283, Issue 42, 28413-28425, October 17, 2008

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Oxygen- and NssR-dependent Globin Expression and Enhanced Iron Acquisition in the Response of Campylobacter to Nitrosative Stress^*

Claire E. Monk¹, Bruce M. Pearson, Francis Mulholland, Holly K. Smith, and Robert K. Poole²

From the Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, United Kingdom and Institute of Food Research, Colney Lane, Norwich Research Park, Colney, Norwich, NR4 7UA, United Kingdom

Pathogenic bacteria experience nitrosative stress from NO generated in the host and from nitrosating species such as S-nitrosoglutathione. The food-borne pathogen Campylobacter jejuni responds by activating gene expression from a small regulon under the control of the NO-sensitive regulator, NssR. Here, we describe the full extent of the S-nitrosoglutathione response using transcriptomic and proteomic analysis of batch- and chemostat-cultured C. jejuni. In addition to the NssR regulon, which includes two hemoglobins (Cgb and Ctb), we identify more than 90 other up-regulated genes, notably those encoding heat shock proteins and proteins involved in oxidative stress tolerance and iron metabolism/transport. Up-regulation of a subset of these genes, including cgb, is also elicited by NO-releasing compounds. Mutation of the iron-responsive regulator Fur results in insensitivity of growth to NO, suggesting that derepression of iron-regulated genes and augmentation of iron acquisition is a physiological response to nitrosative damage. We describe the effect of oxygen availability on nitrosative stress tolerance; cells cultured at higher rates of oxygen diffusion have elevated levels of hemoglobins, are more resistant to inhibition by NO of both growth and respiration, and consume NO more rapidly. The oxygen response is mediated by NssR. Thus, in addition to NO detoxification catalyzed by the hemoglobins Cgb and possibly Ctb, C. jejuni mounts an extensive stress response. We suggest that inhibition of respiration by NO may increase availability of oxygen for Cgb synthesis and function.

Received for publication, February 7, 2008 , and in revised form, July 22, 2008.

^* This work was supported by the Biotechnology and Biological Sciences Research Council, Swindon, United Kingdom. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Tables S1–S3 and Fig. S1.

¹ Present address: MRC Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.

² To whom correspondence should be addressed: Dept. of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, UK. Tel.: 44-114-222-4447; Fax: 44-114-222-2800; E-mail: r.poole{at}sheffield.ac.uk.

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