Thiosulfate Formation Research Articles

Formation of thiosulfate and trithionate during sulfite reduction by washed cells of Desulfovibrio desulfuricans

Deenergized cells of Desulfovibrio desulfuricans strain Essex 6 formed trithionate and thiosulfate during reduction of sulfite with H2 or formate. The required conditions were pretreatment with the uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP), low concentration of the electron donor H2 or formate (25–200 μM) and the presence of sulfite in excess (>250 μM). The cells formed up to 20 μM thiosulfate, and variable amounts of trithionate (0–9 μM) and sulfide (0–62 μM). Tetrathionate was not produced. Sulfate could not replace sulfite in these experiments, as deenergized cells cannot activate sulfate. However, up to 5 μM thiosulfate was produced by cells growing with H2 and excess sulfate in a chemostat. Micromolar concentrations of trithionate were incompletely reduced to thiosulfate and sulfide by washed cells in the presence of CCCP. Millimolar trithionate concentrations blocked the formation of sulfide, even in the absence of CCCP, and caused thiosulfate accumulation; sulfide formation from sulfate, sulfite or thiosulfate was stopped, too. Trithionate reduction with H2 in the presence of thiocyanate was coupled to respiration-driven proton translocation (extrapolated H+/H2 ratios of 1.5±0.6). Up to 150 μM trithionate was formed by washed cells during oxidation of sulfite plus thiosulfate with ferricyanide as electron acceptor (reversed trithionate reductase activity). Cell breakage resulted in drastic decrease of sulfide formation. Cell-free extract reduced sulfite incompletely to trithionate, thiosulfate, and sulfide. Thiosulfate was reduced stoichiometrically to sulfite and sulfide (thiosulfate reductase activity). The formation of sulfide from sulfite, thiosulfate or trithionate by cell-free extract was blocked by methyl viologen, leading to increased production of thiosulfate plus trithionate from sulfite, or increased thiosulfate formation from trithionate. Our study demonstrates for the first time the formation of intermediates during sulfite reduction with whole cells of a sulfate-reducing bacterium oxidizing physiological electron donors. All results are in accordance with the trithionate pathway of sulfite reduction.

Disruption of a rhodaneselike gene results in cysteine auxotrophy in Saccharopolyspora erythraea

A 3,373-base-pair DNA segment from a clone fortuitously isolated from Saccharopolyspora erythraea by hybridization to an oligodeoxynucleotide probe was sequenced. Computer-assisted analysis of the nucleotide sequence reveals three closely linked Streptomyces open reading frames plus a fourth converging on the others. The deduced product of one of them, ORF2, shows considerable similarity to bovine liver rhodanese. orf2, and the closely linked orf3 located just downstream of it, were disrupted by insertion of an apramycin resistance cassette into the orf2 coding sequence along with inversion of the fragment carrying most of orf2 and orf3 via two successive recombinational events in the wild-type strain. The mutant strain thus created contains wild-type levels of rhodanese activity but cannot grow on minimal medium. It is a cysteine auxotroph, capable of utilizing efficiently only thiosulfate among the inorganic sulfur sources tested. orf2 has been designated cysA. The possible role of the rhodaneselike cysA gene product in thiosulfate formation is discussed.

Pyrite oxidation and reduction: Molecular orbital theory considerations

It is possible to demonstrate a heterogeneous reaction mechanism for both pyrite oxidation and reduction using a molecular orbital theory approach. The mechanism demonstrates that attachment to the FeS 2 surface by an oxidant or reductant requires that they have a vacant orbital (solution phase) or site (solid phase) to bind the oxidant or reductant to a sulfur from S 2− 2 in FeS 2. The approach thus requires the formation of a persulfido (disulfide) bridge between the iron in pyrite and the oxidant ( e.g. Fe 3+) or the reductant ( e.g. Cr 2+). The first electron transfer in oxidation occurs from the π ∗ ; orbital (highest occupied molecular orbital, HOMO) of the S 2− 2 in FeS 2 to the π orbital (lowest unoccupied molecular orbital, LUMO) of the oxidant. Electron transfer in reduction occurs from the σ ∗ orbital (HOMO) of the reductant to the σ ∗ orbital (LUMO) of the S 2− 2 in FeS 2. The bridge formation between two metals by a common ligand (persulfido), and the electron transfer, is consistent with an inner sphere type mechanism. In FeS 2, however, the ligand S 2− 2 acts as the electron source or sink rather the Fe 2+. The strength of the sulfur-sulfur bond in the persulfido bridge after electron transfer is key to the understanding of FeS 2 oxidation and reduction. Additional bridges can be formed on the FeS 2 surface during oxidation until the initial oxidation product S 2O 2− 3 is produced. The proposed mechanism allows for facile pyrite oxidation by Fe 3+ but not O 2. This is consistent with experimental observations. The mechanism does not require the formation of a free radical in solution. It does predict the formation of an ion radical on the pyrite surface. The proposed mechanism gives the same initial intermediate (FeS 2O) as recently proposed by Moses et al. (1987), but explains possible surface attachment by an oxidant and subsequent FeS 2 oxidation using a molecular orbital theory approach. The proposed surface mechanism is consistent with experimental observations of several investigators ( Goldhaber, 1983; McKibben and Barnes, 1986; Wiersma and Rimstidt, 1984). The importance of thiosulfate formation and reactivity with Fe 3+ is discussed in light of pyrite oxidation and of previous reports on the presence of thiosulfate in marine porewaters

Scrubbing of hydrogen sulphide using PH control to control thiosulfate formation : Guenter Weber, Linden, Federal Republic Of Germany assigned to Linde Aktiengesellschaft

Scrubbing of hydrogen sulphide using PH control to control thiosulfate formation : Guenter Weber, Linden, Federal Republic Of Germany assigned to Linde Aktiengesellschaft

4434146 Scrubbing of hydrogen sulphide using PH control to control thiosulfate formation : Guenter Weber, Linden, Federal Republic Of Germany assigned to Linde Aktiengesellschaft

4434146 Scrubbing of hydrogen sulphide using PH control to control thiosulfate formation : Guenter Weber, Linden, Federal Republic Of Germany assigned to Linde Aktiengesellschaft

Sulfur isotope fractionation by Salmonella heidelberg: inverse isotope effects during growth on high concentrations of Na2SO3.

During growth on minimal salts - glucose media supplemented with high concentrations of Na2SO3 (10-3 and 10-2 M), Salmonella heidelberg exhibited cytological and growth responses which indicated increased cellular toxicity with increasing sulfite concentrations. The large quantities of sulfide evolved during growth at both SO32- concentrations were accompanied by large normal and inverse isotope effects. Consistent with earlier findings, this organism was found capable of rapidly metabolizing both the sulfane and sulfonate sulfur of thiosulfate. Therefore, the isotope effects do not appear to be caused by extracellular chemical thiosulfate formation.

Thiosulfate formation and associated isotope effects during sulfite reduction by Clostridium pasteurianum.

During growth of Clostridium pasteurianum on sulfite, approximately half the sulfite was reduced to sulfide and half to thiosulfate. Sulfide was enriched in 32S or 34S at different stages of growth and thiosulfate was enriched in 32S, particularly in the sulfane atom. It is suggested that thiosulfate in these bacterial cultures arose from a secondary chemical reaction. The chemical formation of thiosulfate from sulfide and sulfite was also accompanied by sulfur isotope fractionation. The implications of these results with respect to 'inverse' isotopic effects are discussed.

Characterization of a novel thiosulfate-forming enzyme isolated from Desulfovibrio vulgaris

An enzyme that formed thiosulfate from bisulfite and trithionate was purified from extracts of Desulfovibrio vulgaris. This enzyme, designated as "thiosulfate-forming" enzyme, required the presence of both bisulfite and trithionate. Various 35S-labeling studies showed that thiosulfate was formed from bisulfite and the inner sulfur atom of trithionate. This involved a nucleophilic attack by the bisulfite ion, resulting in the displacement of the two outer sulfonate groups of trithionate that recycled to participate as free bisulfite in subsequent reactions. This reaction required a reduction, presumably by a concerted mechanism with thiosulfate formation. The natural electron carrier cytochrome c3 participated in this reductive formation of thiosulfate. This reaction was coupled to the bisulfite reductase-catalyzed reaction, which resulted in the reconstruction of a thiosulfate-forming pathway from bisulfite.

Purification of a unique bisulfite-reducing enzyme from [formula omitted

An enzyme which catalyzes the reduction of bisulfite to sulfide and thiosulfate was purified from extracts of the sulfate-reducing bacterium, Desulfovibrio vulgaris . Trithionate was not a product of this reaction nor was it or thiosulfate reduced by the enzyme. High substrate concentrations inhibited sulfide but not thiosulfate formation. The enzyme was named bisulfite reductase II to distinguish it from bisulfite reductase which reduces bisulfite to trithionate.

Studies of Sulfate Utilization by Algae

Seven mutants of Chlorella pyrenoidosa (Emerson strain 3) impaired for sulfate utilization have been isolated after treatment of the wild-type organism with nitrosoguanidine by replica plating on media containing thiosulfate and l-methionine. These mutants fall into three classes based on their ability to grow on sulfate, accumulate compounds labeled from sulfate-(35)S, and reduce adenosine 3'-phosphate 5'-phosphosulfate-(35)S (PAPS-(35)S) to thiosulfate-(35)S. Mutant Sat(2) (-) cannot grow on sulfate, but it accumulates thiosulfate-(35)S and homocysteic acid-(35)S from sulfate-(35)S in vivo. In addition, extracts of mutant Sat(2) (-) reduce PAPS-(35)S to thiosulfate-(35)S, indicating the possession of enzyme fractions S and A, both of which are required for thiosulfate formation. Mutants Sat(1) (-), Sat(3) (-), Sat(4) (-), Sat(5) (-), and Sat(6) (-) cannot grow on sulfate, and their extracts lack the ability to reduce PAPS-(35)S to thiosulfate-(35)S. Mutant Sat(7) (-)R(1), a probable revertant, can grow on sulfate but still lacks the ability to reduce PAPS-(35)S to thiosulfate-(35)S in vitro. Complementation experiments in vitro show that the block in formation of acid-volatile radioactivity in every case is due to the absence of activity associated with fraction S. All mutants can grow on thiosulfate and all possess the activating enzymes which convert sulfate to PAPS. Through a comparison of nutritional and enzymatic characteristics, the first outlines of a branched and complicated pathway for sulfate reduction in Chlorella are beginning to emerge.

Evidence for thiosulfate formation during sulfite reduction by Desulfovibrio vulgaris

The sulfate-reducing bacterium, Desulfovibrio vulgaris, reduces sulfite to sulfide which accumulates as the end product of sulfate metabolism. When the course of the reduction was followed by analyzing reaction mixtures for sulfide and thiosulfate, the latter compound was observed to accumulate and eventually disappear. However, the sulfide concentration gradually increased and its accumulation was concomitant with thiosulfate disappearance. The results indicate that thiosulfate is one of the intermediate compounds which is formed during dissimilatory sulfite reduction.

Studies of Sulfate Utilization by Algae. 5. Identification of Thiosulfate as a Major Acid-Volatile Product Formed by a Cell-Free Sulfate-Reducing System From Chlorella

Separation of the products formed from sulfate-(35)S by cell-free extracts of Chlorella pyrenoidosa (Emerson Strain 3) has permitted the identification of thiosulfate as a major product which yields acid-volatile radioactivity. The products formed, as separated by Dowex-1-nitrate chromatography, are qualitatively the same whether extracts at pH 7.0 (using TPNH as the reductant) or extracts at pH 9 [using 2,3-dimercaptopropan-1-ol, (BAL) as reductant] are employed. While thiosulfate can be separated without the addition of carrier, the inclusion of carrier improves the recovery. High concentrations of ATP which have been shown previously to inhibit the formation of acid-volatile radioactivity from radioactive sulfate, inhibit the formation of thiosulfate almost completely. Degradation of the thiosulfate formed at normal ATP concentrations reveals that most of the radioactivity is in the SO(3)-sulfur of the molecule suggesting that the SH-sulfur is derived from the enzyme extracts. If carrier sulfite is present during thiosulfate formation from sulfate-(35)S, radioactive sulfite is recovered at the expense of radioactive thiosulfate. Reconstruction experiments utilizing specifically-labeled thiosulfates indicate that radioactive sulfite formation is probably not the result of trapping a normal intermediate, but can be attributed to non-enzymatic exchange between labeled thiosulfate formed from sulfate and the non-radioactive sulfite added, suggesting that free sulfite is not an intermediate in thiosulfate formation from sulfate.

Studies of Sulfate Utilization by Algae. 6. Adenosine-3′-Phosphate-5′-Phosphosulfate (PAPS) as an Intermediate in Thiosulfate Formation From Sulfate by Cell-Free Extracts of Chlorella

When cell-free preparations of Chlorella pyrenoidosa Chick (Emerson strain 3) form thiosulfate from labeled sulfate, another radioactive compound also appears. This compound has been isolated in quantity and is shown to be identical with adenosine-3'-phosphate-5'-phosphosulfate (PAPS) on the basis of its chromatographic and electrophoretic behavior, chemical composition, sensitivity to selective degradative enzymes, and its ability to serve as a substrate for rat liver aryl sulphotransferase. In addition, as expected for PAPS, the compound on mild acid treatment yields all of its radioactive sulfur as sulfate, and is converted to a compound identical with adenosine-3',5'-diphosphate (PAP). Replacement of sulfate and ATP by this PAP(35)S in the usual incubation mixture yields the same product, thiosulfate, which can be isolated as such or detected as acid-volatile radioactivity. This conversion of PAP(35)S to thiosulfate still requires the addition of Mg(2+) and a reductant such as 2,3-dimercaptopropan-1-ol (BAL). The cause of our previous result that high concentrations of ATP inhibit thiosulfate formation from sulfate can be ascribed to a small amount of PAP contaminating the ATP preparations, since PAP proves to be an exceedingly effective inhibitor of the conversion of PAP(35)S to thiosulfate. Sulfate reduction to thiosulfate by Chlorella extracts is discussed and compared with similar systems from other organisms.