Project Summary
Campylobacter jejuni is the leading cause of bacterial-derived gastroenteritis in the world. Human
infection often occurs through the ingestion of contaminated food, especially poultry, which leads to the
bacterium colonizing the colon and causing severe inflammation and diarrhea. While infection and disease is
often self-limiting, persistent colonization and chronic diseases do occur. Despite the significant impacts of C.
jejuni on human health, very little is known about the interactions that occur at the host-pathogen interface during
infection, including how C. jejuni senses and adapts to the host intestinal environment to promote infection. This
is primarily due to the evolutionary divergence of this organism from other gastrointestinal pathogens, which
limits the relevance of findings from those organisms and necessitates specific study of the Campylobacter
genus. To that end, our group previously identified a unique regulator in C. jejuni, which we call HeuR, that
promotes maximum colonization of a natural avian host and was subsequently found to positively or negatively
regulate several genetic determinants, including those involved in the acquisition of iron from host heme and the
biosynthesis of methionine. In addition, HeuR and its downstream targets are required for efficient invasion or
persistence in human colonocytes, which suggests these mechanisms need to be better understood as they are
clearly involved in infection of animals.
We preliminarily determined that this novel regulator binds several TCA intermediates and may sense
TCA cycle activity to control expression of colonization determinants. First, we will define all direct targets of
HeuR and examine whether TCA intermediates impact the ability of HeuR to bind those DNA targets and impact
gene expression. Additionally, we will identify the ligand binding motif of this novel regulator and how it facilitates
HeuR activity. Second, because we have determined that C. jejuni TCA intermediate abundance is affected by
iron-restriction, we will use mass isotopomer analysis to identify the points along the C. jejuni TCA cycle that are
affected by iron-limitation and determine whether altering TCA cycle activity affects HeuR-dependent
colonization determinant expression. In addition, we will directly determine the levels at which each TCA enzyme
indicated by mass isotopomer analysis is affected by iron-limitation. Lastly, one of the direct targets of HeuR we
identified that may be impacted by TCA intermediate-dependent binding is the heme utilization system of C.
jejuni. This system is poorly characterized in C. jejuni and we will examine whether this system facilitates iron
acquisition during animal infection and will work to fully characterize the process of heme utilization so that it can
be leveraged in future studies to inhibit the infection potential of C. jejuni.
