Efficient gastrointestinal colonization by Campylobacter jejuni requires components of the ChuABCD heme transport system

Previous research demonstrated that Campylobacter jejuni encodes a heme utilization system that facilitates heme-dependent growth under iron-limiting conditions and that transcription of this system is induced during human infection. Despite these observations, it remained unknown whether the heme transport system is required for colonization and disease in a susceptible host. To address this, we created individual non-polar deletion mutants of each component of the heme transport system, as well as a total deletion of the inner membrane transporter, ChuBCD, and examined their ability to promote heme-dependent growth and iron uptake. From this work, we found that only the heme receptor, ChuA, was required for heme-dependent growth and iron acquisition, which supports earlier work of another group. Further, we examined whether intestinal colonization, immune activation, and pathology were altered during infection with these mutants. After establishing that elevated heme and chuABCD expression occurs during C. jejuni infection of IL-10-/- mice, we found that heme transport mutants exhibited significantly reduced fecal shedding and colonization of the cecum and colon. In addition, we found that neutrophil and macrophage recruitment and intestinal pathology often remained intermediately elevated despite decreased bacterial loads. These results suggest that heme utilization promotes efficient colonization and full pathogenicity in C. jejuni, but that neither is completely abrogated in its absence.