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Identification of Campylobacter jejuni Genes Contributing to Acid Adaptation by Transcriptional Profiling and Genome-Wide Mutagenesis

Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada,¹ Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, Oklahoma 74078²

Received 4 July 2007/ Accepted 30 December 2007

In order to cause disease, the food- and waterborne pathogen Campylobacter jejuni must face the extreme acidity of the host stomach as well as cope with pH fluctuations in the intestine. In the present study, C. jejuni NCTC 11168 was grown under mildly acidic conditions mimicking those encountered in the intestine. The resulting transcriptional profiles revealed how this bacterium fine-tunes gene expression in response to acid stress. This adaptation involves the differential expression of respiratory pathways, the induction of genes for phosphate transport, and the repression of energy generation and intermediary metabolism genes. We also generated and screened a transposon-based mutant library to identify genes required for wild-type levels of growth under mildly acidic conditions. This screen highlighted the important role played by cell surface components (flagella, the outer membrane, capsular polysaccharides, and lipooligosaccharides) in the acid stress response of C. jejuni. Our data also revealed that a limited correlation exists between genes required for growth under acidic conditions and genes differentially expressed in response to acid. To gain a comprehensive picture of the acid stress response of C. jejuni, we merged transcriptional profiles obtained from acid-adapted cells and cells subjected to acid shock. Genes encoding the transcriptional regulator PerR and putative oxidoreductase subunits Cj0414 and Cj0415 were among the few up-regulated under both acid stress conditions. As a Cj0415 mutant was acid sensitive, it is likely that these genes are crucial to the acid stress response of C. jejuni and consequently are important for host colonization.

Published ahead of print on 11 January 2008.

This article has been cited by other articles:

• Reid, A. N., Pandey, R., Palyada, K., Naikare, H., Stintzi, A. (2008). Identification of Campylobacter jejuni Genes Involved in the Response to Acidic pH and Stomach Transit. Appl. Environ. Microbiol. 74: 1583-1597 [Abstract] [Full Text]