The PAS domain-containing protein HeuR regulates heme uptake in Campylobacter jejuni

Abstract

Campylobacter jejuni is a leading cause of bacterial-derived gastroenteritis. A previous mutant screen demonstrated that the heme uptake system (Chu) is required for full colonization of the chicken gastrointestinal tract. Subsequent work found identified a PAS domain-containing regulator, termed HeuR, as required for chicken colonization. Here we confirmthat both the heme uptake system and HeuR are required for full chicken gastrointestinal tract colonization, with the heuR mutant being particularlyaffected during competition with wild-type C. jejuni. Transcriptomic analysis identified the chu genes-and those encoding other iron uptake systems-as likely regulatory targets of HeuR. Purified HeuR specifically bound the chuZA promoter region in electrophoretic mobility shift assays. Consistentwith a role forHeuR in chu expression, heuR mutants wereunable to efficiently use heme asa source of iron in iron-limitingconditions and, mutants exhibited decreased levels of cell-associated ironby massspectrometry.Finally, we demonstrate that a heuR mutant of C. jejuni isresistant to hydrogen peroxide, and that this resistance correlates to elevated levels ofcatalase activity.\n\nAuthor SummaryCampylobacter jejuni causes millions of gastrointestinal infection every year. This is primarily due to the its ability to reside in the gastrointestinal tract of chickens. C.jejuni contaminates chicken meat during harvesting and processing. Following consumption of undercooked chicken or uncooked food that was contaminated with raw chicken juice, humans develop a debilitating illness that is characterized by diarrhea and abdominal cramps. As chickens are the source of most human infections, there is a need to understand how C. jejuni colonizes chickens so we can develop ways to reduce its presence in chickens and thereby improve food safety. Most organisms require iron to thrive and that some bacteria steal iron from host molecules, including hemoglobin. Here we demonstrate that C. jejuni may need to get iron from hemoglobin in order to colonize the chicken and that aregulatory protein, HeuR, controls the ability ofthe bacteria to do this. If we can understand how this protein works, we may be able to develop ways to inhibit its function and reduce the ability of C. jejuni to get iron during chicken colonization. This would limit theamount of C. jejuni in the chicken and make food safer.