title: Sulfide oxidation in the phototrophic sulfur bacterium Chromatium vinosum.
abstract: Sulfide oxidation in the phototrophic purple sulfur bacterium Chromatium vinosum D (DSMZ 180(T)) was studied by insertional inactivation of the fccAB genes, which encode flavocytochrome c, a protein that exhibits sulfide dehydrogenase activity in vitro. Flavocytochrome c is located in the periplasmic space as shown by a PhoA fusion to the signal peptide of the hemoprotein subunit. The genotype of the flavocytochrome-c-deficient Chr. vinosum strain FD1 was verified by Southern hybridization and PCR, and the absence of flavocytochrome c in the mutant was proven at the protein level. The oxidation of thiosulfate and intracellular sulfur by the flavocytochrome-c-deficient mutant was comparable to that of the wild-type. Disruption of the fccAB genes did not have any significant effect on the sulfide-oxidizing ability of the cells, showing that flavocytochrome c is not essential for oxidation of sulfide to intracellular sulfur and indicating the presence of a distinct sulfide-oxidizing system. In accordance with these results, Chr. vinosum extracts catalyzed electron transfer from sulfide to externally added duroquinone, indicating the presence of the enzyme sulfide:quinone oxidoreductase (EC 1.8.5.-). Further investigations showed that the sulfide:quinone oxidoreductase activity was sensitive to heat and to quinone analogue inhibitors. The enzyme is strictly membrane-bound and is constitutively expressed. The presence of sulfide:quinone oxidoreductase points to a connection of sulfide oxidation to the membrane electron transport system at the level of the quinone pool in Chr. vinosum.
authors.affiliation: Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Meckenheimer Allee 168, D-53115 Bonn, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Reinartz
authors.forename: J
authors.initials: J
authors.lastname: Tschäpe
authors.forename: T
authors.initials: T
authors.lastname: Brüser
authors.forename: H G
authors.initials: HG
authors.lastname: Trüper
authors.forename: C
authors.initials: C
authors.lastname: Dahl
mesh_terms: D001483:Base Sequence; D015139:Blotting, Southern; D002844:Chromatium / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D003574:Cytochrome c Group / Q000235:genetics / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000502:physiology*; D016133:Polymerase Chain Reaction; D011808:Quinone Reductases / Q000378:metabolism*; D013885:Thiosulfates / Q000378:metabolism
chemical_list: D003574:Cytochrome c Group; D013885:Thiosulfates; D010088:Oxidoreductases; D011808:Quinone Reductases; C064500:flavocytochrome c sulfide dehydrogenase; C073412:sulfide quinone reductase