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

Abstract

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.

Campylobacter jejuni Glycosylation Island Important in Cell Charge, Legionaminic Acid Biosynthesis, and Colonization of Chickens

“…Gene-specific disruption of Cj1321, Cj1322, Cj1323, Cj1324, or Cj1325/6 or the removal of the entire locus (Cj1321 to Cj1325/6) did not affect motility. This finding supports recently published data from Reid et al, who reported that the motility of a Cj1324 transposon mutant was unaffected compared to that of the wild type (45), and data from previous studies of genes involved in the ptm pathway, which have shown that mutagenesis in Cj1332 (ptmA) and Cj1331 (ptmB) does affect motility (20,62). The presence of flagella facilitated a top-down MS analysis of selected mutants to determine whether genes in the Cj1321-Cj1325/6 locus encode novel glycan modifications to flagellin in strain 11168H.…”

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

“…The scavengase p20s appear important in pathogenesis (78), where nitrosative stress may be encountered. Several genes identified as up-regulated by GSNO in the present study (notably cgb and putative oxidoreductase genes Cj0414 and Cj0415) were also increased in a recent transcriptomic analysis of C. jejuni growing under mildly acidic conditions (79), but the significance of this cannot be explained at present.…”

Campylobacter jejuni proteins Cj0952c and Cj0951c affect chemotactic behaviour towards formic acid and are important for invasion of host cells

“…Signature-tagged transposon mutagenesis has shown Campylobacter colonization in chickens to be complex and dynamic (Grant et al, 2005), and furthermore, screening of a transposon-based mutant library has identified C. jejuni genes that are related to polymyxin resistance and to acid adaptation of the pathogen (Lin et al, 2009;Reid et al, 2008). Additionally, transposon mutagenesis in a clinical isolate of C. jejuni has detected 26 mutants with a clearly reduced invasion capacity (Javed et al, 2010).…”