title: Function and Regulation of the C4-Dicarboxylate Transporters inCampylobacter jejuni.
abstract: C4-dicarboxylates are important molecules for the human pathogenC.jejuni, as they are used as carbon and electron acceptor molecules, as sugars cannot be utilized by this microaerophilic organism. Based on the genome analysis,C. jejunimay possess five different C4-dicarboxylate transporters: DctA, DcuA, DcuB, and two homologs of DcuC. Here, we investigated the regulation and function of various C4-dicarboxylate transporters inC. jejuni. Transcription of thedctAanddcuChomologs is constitutive, whiledcuAanddcuBare both directly regulated by the two-component RacR/RacS system in response to limited oxygen availability and the presence of nitrate. The DctA transporter is the only C4-dicarboxylate transporter to allowC. jejunito grow on C4-carbon sources such as aspartate, fumarate, and succinate at high oxygen levels (10% O2) and is indispensable for the uptake of succinate from the medium under these conditions. Both DcuA and DcuB can sequester aspartate from the medium under low-oxygen conditions (0.3% O2). However, under these conditions, DcuB is the only transporter to secrete succinate to the environment. Under low-oxygen conditions, nitrate prevents the secretion of succinate to the environment and was able to overrule the phenotype of the C4-transporter mutants, indicating that the activity of the aspartate-fumarate-succinate pathway inC. jejuniis strongly reduced by the addition of nitrate in the medium.
authors.affiliation: Department of Infectious Diseases and Immunology, Utrecht University Utrecht, Netherlands.
authors.forename: Marc M S M
authors.initials: MM
authors.lastname: Wösten
authors.affiliation: Department of Biochemistry and Cell Biology, Utrecht University Utrecht, Netherlands.
authors.forename: Chris H A
authors.initials: CH
authors.lastname: van de Lest
authors.affiliation: Department of Infectious Diseases and Immunology, Utrecht University Utrecht, Netherlands.
authors.forename: Linda
authors.initials: L
authors.lastname: van Dijk
authors.affiliation: Department of Infectious Diseases and Immunology, Utrecht University Utrecht, Netherlands.
authors.forename: Jos P M
authors.initials: JP
authors.lastname: van Putten
keywords: C4-dicarboxylates transporters; Campylobacter jejuni; DctA; Dcu; RacRS; gene regulation; metabolism