ISSN:
1432-072X
Keywords:
Key wordsChromatium vinosum
;
Flavocytochrome c
;
Sulfide:quinone oxidoreductase
;
Sulfide oxidation
;
Phototrophic sulfur bacteria
;
Interposon mutagenesis
;
phoA fusion
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Sulfide oxidation in the phototrophic purple sulfur bacterium Chromatium vinosum D (DSMZ 180T) 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002030050615
