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  • 1
    ISSN: 1432-072X
    Keywords: Sulphur respiration ; Electrochemical proton potential ; Wolinella succinogenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Wolinella succinogenes grown on formate and elemental sulphur was found to use the polysulphide derivatives 2,2′-tetrathiobispropionate (R2S4) or pentathionate (S5O 6 = ) as acceptors for formate oxidation. The specific activities of formate oxidation with these acceptors were similar to those with elemental sulphur. The main reaction products of R2S4 reduction were 2,2′-dithiobispropionate (R2S2) and sulphide. Pentathionate was converted to thiosulphate and some elemental sulphur. The electrochemical proton potential $$(\Delta \tilde \mu _H )$$ across the cytoplasmic membrane of the bacterium was measured in the steady state of electron transport from formate to R2S4. The electrical proportion (Δψ) of the $$(\Delta \tilde \mu _H )$$ determined through the distribution of labeled tetraphenylphosphonium cation was obtained as 0.17 Volt. The Δψ was zero, when a protonophore was present. The pH-difference across the membrane was negligible. Thus the $$(\Delta \tilde \mu _H )$$ generated by sulphur respiration is close to that measured earlier with fumarate as the terminal acceptor of electron transport.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Keywords: Sulphur respiration ; Polysulphide ; Electron transport ; Wolinella succinogenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Polysulphide was formed according to reaction (1), when tetrathionate was (1) $${\text{S}}_4 {\text{O}}_6^{2 - } + {\text{HS}}^ - \to 2{\text{S}}_2 {\text{O}}_3^{2 - } + {\text{S(O)}} + {\text{H}}^ + $$ added to an anaerobic buffer (pH 8.5) containing excess sulphide. S(O) denotes the zero oxidation state sulphur in the polysulphide mixture S infn sup2- . The addition of formate to the polysulphide solution in the presence of Wolinella succinogenes caused the reduction of polysulphide according to reaction (2). The bacteria grew in a medium containing formate and sulphide, (2) $${\text{HCO}}_2^ - + {\text{S(O)}} + {\text{H}}2{\text{O}} \to {\text{HCO}}_3^ - + {\text{HS}}^ - + {\text{H}}^ + $$ when tetrathionate was continuously added. The cell density increased proportional to reaction (3) which represents the sum of reactions (1) and (3) $${\text{HCO}}_2^ - + {\text{S}}_{\text{4}} {\text{O}}_6^{2 - } + {\text{H}}2{\text{O}} \to {\text{HCO}}_3^ - + 2{\text{S}}_{\text{2}} {\text{O}}_3^{2 - } + 2{\text{H}}^ + $$ (2). The cell yield per mol formate was nearly the same as during growth on formate and elemental sulphur, while the velocity of growth was greater. The specific activities of polysulphide reduction by formate measured with bacteria grown with tetrathionate or with elemental sulphur were consistent with the growth parameters. The results suggest that W. succinogenes grow at the expense of formate oxidation by polysulphide and that polysulphide is an intermediate during growth on formate and elemental sulphur.
    Type of Medium: Electronic Resource
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