Campylobacter jejuni is the most frequent cause of severe
gastroenteritis in the developed world. The major symptom of
campylobacteriosis is inflammatory diarrhoea. The molecular mechanisms of this
infection are poorly understood compared to those of less frequent disease-causing pathogens. In a previous study, we identified C. jejuni
proteins that
antibodies in human
campylobacteriosis patients reacted with. One of the immunogenic
proteins identified (Cj0917) displays homology to
carbon starvation protein A (CstA) from Escherichia coli, where this
protein is involved in the
starvation response and
peptide uptake. In contrast to many bacteria, C. jejuni relies on
amino acids and organic
acids for energy, but in vivo it is highly likely that
peptides are also utilized, although their mechanisms of uptake are unknown. In this study, Biolog phenotype microarrays have been used to show that a ΔcstA mutant has a reduced ability to utilize a number of di- and tri-
peptides as
nitrogen sources. This phenotype was restored through genetic complementation, suggesting CstA is a
peptide uptake system in C. jejuni. Furthermore, the ΔcstA mutant also displayed reduced motility and reduced agglutination compared to WT bacteria; these phenotypes were also restored through complementation. Murine dendritic cells exposed to UV-killed bacteria showed a reduced
IL-12 production, but the same
IL-10 response when encountering C. jejuni ΔcstA compared to the WT strain. The greater Th1 stimulation elicited by the WT as compared to ΔcstA mutant cells indicates an altered antigenic presentation on the surface, and thus an altered recognition of the mutant. Thus, we conclude that C. jejuni CstA is important not only for
peptide utilization, but also it may influence host-pathogen interactions.