Identification and characterization of a periplasmic trilactone esterase, Cee , revealed unique features of ferric enterobactin acquisition in C ampylobacter

Summary Ferric enterobactin ( FeEnt ) acquisition is a highly efficient and conserved iron scavenging system in G ram‐negative bacteria. Recently, we have characterized two FeEnt receptors ( CfrA and CfrB ) in C ampylobacter jejuni and C . coli , the enteric human pathogens that do not produce any siderophores. In this study, whole‐genome sequencing and comparative genomic analysis identified a unique Ent trilactone esterase Cee ( Cj 1376) in C . jejuni . Genomic analysis and biochemical assay strongly suggested that Cee is the sole trilactone esterase in C . jejuni . Thin‐layer chromatography and HPLC analyses showed high efficiency of the purified Cee to hydrolyse Ent . Three Cee homologues previously characterized from other bacteria ( IroE , IroD and Fes ) were also purified and analysed together with Cee , indicating that Cee , Fes and IroD displayed similar hydrolysis dynamics for both apo and ferric forms of Ent while IroE catalysed Ent inefficiently. Unlike cytoplasmic Fes and IroD , Cee is localized in the periplasm as demonstrated by immunoblotting using Cee ‐specific antibodies. Genetic manipulation of diverse C ampylobacter strains demonstrated that Cee is not only essential for CfrB ‐dependent FeEnt acquisition but also involved in CfrA ‐dependent pathway. Together, this study identified and characterized a novel periplasmic trilactone esterase and suggested a new model of FeEnt acquisition in C ampylobacter .