Dissecting components of theCampylobacter jejuni fetMP-fetABCDEFgene cluster in iron scavenging

Abstract

ABSTRACTCampylobacter jejuniis a leading cause of bacterial gastroenteritis worldwide. Acute infection can be antecedent to highly debilitating long-term sequelae. Expression of iron acquisition systems is vital forC. jejunito survive the low iron availability within the human gut. TheC. jejuni fetMP-fetABCDEFgene cluster is known to be upregulated during human infection and under iron limitation. While FetM and FetP have been functionally linked to iron transport in prior work, here we assess the contribution by each of the downstream genes (fetABCDEF) toC. jejunigrowth during both iron-depleted and iron-replete conditions. Significant growth impairment was observed upon disruption offetA,fetB, fetC, andfetD, suggesting a role in iron acquisition for each encoded protein. FetA expression was modulated by iron-availability but not dependent on the presence of FetB, FetC, FetD, FetE or FetF. Functions of the putative thioredoxins FetE and FetF were redundant in iron scavenging, requiring a double deletion (ΔfetEF) to exhibit a growth defect.C. jejuniFetE was expressed and the structure solved to 1.50 Å, revealing structural similarity to thiol-disulfide oxidases. Functional characterization in biochemical assays showed that FetE reduced insulin at a slower rate thanE. coliTrx and that together, FetEF promoted substrate oxidation in cell extracts, suggesting that FetE (and presumably FetF) are oxidoreductases that can mediate oxidationin vivo. This study advances our understanding of the contributions by thefetMP-fetABCDEFgene cluster to virulence at a genetic and functional level, providing foundational knowledge towards mitigatingC. jejuni-related morbidity and mortality.