No abstract

An attenuated Campylobacter jejuni aspartate chemoreceptor ccaA mutant caused gross pathological changes despite reduced colonisation ability in animal models. In chickens, the pathological changes included connective tissue and thickening of the mesenteric fat, as well as the disintegration of the villus tips in the large intestine, whereas in mice, hepatomegaly occurred between 48–72 hours post infection and persisted for the six days of the time course. In addition, there was a significant change in the levels of IL-12p70 in mice infected with the C. jejuni ccaA mutant. CcaA isogenic mutant was hyper-invasive in cell culture and microscopic examination revealed that it had a “run” bias in its “run-and-tumble” chemotactic behaviour. The mutant cells also exhibited lower level of binding to fucosylated and higher binding to sialylated glycan structures in glycan array analysis. This study highlights the importance of investigating phenotypic changes in C. jejuni, as we have shown that specific mutants can cause pathological changes in the host, despite reduction in colonisation potential.

The components of the proton pump NADH:ubiquinone (Complex I) of the respiration pathway have been identified in the C. jejuni genome. However, the paradigm genes nuoE and nuoF encoding subunits of the NADH dehydrogenase module of Complex I are absent. Instead the genes cj1575c and cj1574c encoding NuoX and NuoY are present in the loci corresponding to nuoE and nuoF, respectively. Bioinformatics analyses showed the presence of nuoX and nuoY homologues in all sequenced strains of C. jejuni and in other Campylobacter species, as well as the presence of orthologues in other ɛ-Proteobacteria.To understand the involvement of the NuoX and NuoY proteins in the respiration of C. jejuni and to characterize their ligand binding specificity and affinity, a tricarboxylic acid cycle array was developed as a tool to identify proteins that can bind to intermediates of this cycle as well as other metabolites. This array showed that NuoX bound FAD 2+ , and NuoY bound FAD 2+ and the electron donors malate and lactate. Saturation Transfer Difference Nuclear Magnetic Resonance studies confirmed the NuoY binding ligands, and suggested that the flavin moiety of FAD 2+ interacted more strongly with NuoY than the adenine moiety. Affinity data generated by Surface Plasmon Resonance indicated that NuoY bound to FAD 2+ with a K D of 337 nM; NuoX and NuoY had an affinity for NADH of a K D of 403 nM and 478 nM, respectively, and a ten-fold lower affinity for both NAD + and FAD 2+ . The data suggested that the flavin-adenine dinucletoide could be bound preferentially to the NAD in the Complex I of C. jejuni.