title: Two respiratory enzyme systems in Campylobacter jejuni NCTC 11168 contribute to growth on L-lactate.
abstract: Campylobacter jejuni, a major food-borne intestinal pathogen, preferentially utilizes a few specific amino acids and some organic acids such as pyruvate and L- and D-lactate as carbon sources, which may be important for growth in the avian and mammalian gut. Here, we identify the enzymatic basis for C. jejuni growth on L-lactate. Despite the presence of an annotated gene for a fermentative lactate dehydrogenase (cj1167), no evidence for lactate excretion could be obtained in C. jejuni NCTC 11168, and inactivation of the cj1167 gene did not affect growth on lactate as carbon source. Instead, L-lactate utilization in C. jejuni NCTC 11168 was found to proceed via two novel NAD-independent L-LDHs; a non-flavin iron-sulfur containing three subunit membrane-associated enzyme (Cj0075c-73c), and a flavin and iron-sulfur containing membrane-associated oxidoreductase (Cj1585c). Both enzymes contribute to growth on L-lactate, as single mutants in each system grew as well as wild-type on this substrate, while a cj0075c cj1585c double mutant showed no L-lactate oxidase activity and did not utilize or grow on L-lactate; D-lactate-dependent growth was unaffected. Orthologues of Cj0075c-73c (LldEFG/LutABC) and Cj1585c (Dld-II) were recently shown to represent two novel families of L- and D-lactate oxidases; this is the first report of a bacterium where both enzymes are involved in L-lactate utilization only. The cj0075c-73c genes are located directly downstream of a putative lactate transporter gene (cj0076c, lctP), which was also shown to be specific for L-lactate. The avian and mammalian gut environment contains dense populations of obligate anaerobes that excrete lactate; our data indicate that C. jejuni is well equipped to use L- and D-lactate as both electron-donor and carbon source.
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UKInstitute of Food Research, Norwich Research Park, Colney Lane, Norwich NR4 7UA, UK.
authors.forename: Marie T
authors.initials: MT
authors.lastname: Thomas
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UKInstitute of Food Research, Norwich Research Park, Colney Lane, Norwich NR4 7UA, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Shepherd
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UKInstitute of Food Research, Norwich Research Park, Colney Lane, Norwich NR4 7UA, UK.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Poole
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UKInstitute of Food Research, Norwich Research Park, Colney Lane, Norwich NR4 7UA, UK.
authors.forename: Arnoud H M
authors.initials: AHM
authors.lastname: van Vliet
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UKInstitute of Food Research, Norwich Research Park, Colney Lane, Norwich NR4 7UA, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Kelly
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UKInstitute of Food Research, Norwich Research Park, Colney Lane, Norwich NR4 7UA, UK.
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Pearson
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D016123:Campylobacter jejuni / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D005285:Fermentation; D005816:Genetic Complementation Test; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism*; D009154:Mutation; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D019344:Lactic Acid; D007770:L-Lactate Dehydrogenase