Functional Characterization of a Lipoprotein-Encoding Operon in Campylobacter jejuni

Background: Bacterial lipoproteins have important functions in bacterial pathogenesis and physiology. In Campylobacter jejuni, a major foodborne pathogen causing gastroenteritis in humans, the majority of lipoproteins have not been functionally characterized. Previously, we showed by DNA microarray that CmeR, a transcriptional regulator repressing the expression of the multidrug efflux pump CmeABC, modulates the expression of a three-gene operon (cj0089, cj0090, and cj0091) encoding a cluster of lipoproteins in C. jejuni. Methodology/Principal Findings: In this work, we characterized the function and regulation of the cj0089-cj0090-cj0091 operon. In contrast to the repression of cmeABC, CmeR activates the expression of the lipoprotein genes and the regulation is confirmed by immunoblotting using anti-Cj0089 and anti-Cj0091 antibodies. Gel mobility shift assay showed that CmeR directly binds to the promoter of the lipoprotein operon, but the binding is much weaker compared with the promoter of cmeABC. Analysis of different cellular fractions indicated that Cj0089 was associated with the inner membrane, while Cj0091 was located on the outer membrane. Inactivation of cj0091, but not cj0089, significantly reduced the adherence of C. jejuni to INT 407 cells in vitro, indicating that Cj0091 has a function in adherence. When inoculated into chickens, the Cj0091 mutant also showed a defect in early colonization of the intestinal tract, suggesting that Cj0091 contributes to Campylobacter colonization in vivo. It was also shown that Cj0091 was produced and immunogenic in chickens that wer

Unexpected differential metabolic responses of Campylobacter jejuni to the abundant presence of glutamate and fucose

Introduction: Campylobacter jejuni is the leading cause of foodborne bacterial enteritis in humans, and yet little is known in regard to how genetic diversity and metabolic capabilities among isolates affect their metabolic phenotype and pathogenicity. Objectives: For instance, the C. jejuni 11168 strain can utilize both l-fucose and l-glutamate as a carbon source, which provides the strain with a competitive advantage in some environments and in this study we set out to assess the metabolic response of C. jejuni 11168 to the presence of l-fucose and l-glutamate in the growth medium. Methods: To achieve this, untargeted hydrophilic liquid chromatography coupled to mass spectrometry was used to obtain metabolite profiles of supernatant extracts obtained at three different time points up to 24 h. Results: This study identified both the depletion and the production and subsequent release of a multitude of expected and unexpected metabolites during the growth of C. jejuni 11168 under three different conditions. A large set of standards allowed identification of a number of metabolites. Further mass spectrometry fragmentation analysis allowed the additional annotation of substrate-specific metabolites. The results show that C. jejuni 11168 upon l-fucose addition indeed produces degradation products of the fucose pathway. Furthermore, methionine was faster depleted from the medium, consistent with previously-observed methionine auxotrophy. Conclusions: Moreover, a multitude of not previously annotated metabolites in C. jejuni were found to be increased specifically upon l-fucose addition. These metabolites may well play a role in the pathogenicity of this C. jejuni strain.</p