Production Of Thiosulfate Research Articles

Sustainable Recovery of Platinum Group Metals from Spent Automotive Three-Way Catalysts through a Biogenic Thiosulfate-Copper-Ammonia System.

This study explores an eco-friendly method for recovering platinum group metals from a synthetic automotive three-way catalyst (TWC). Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods. Biogenic thiosulfate production was optimized in a gas-lift bioreactor by studying the pH (8-10) and operation modes (batch and continuous) under anoxic and microaerobic conditions for 35 d. The maximum concentration of 4.9 g S2O32- L-1 of biogenic thiosulfate was reached under optimal conditions (batch mode, pH = 10, and airflow rate 0.033 vvm). To optimize Pd bioleaching from a ground TWC, screening through a Plackett-Burman design determined that oxygen and temperature significantly affected the leaching yield negatively and positively, respectively. Based on these results, an optimization through an experimental design was performed, indicating the optimal conditions to be Na2S2O3 1.2 M, CuSO4 0.03 M, (NH4)2SO4 1.5 M, Na2SO3 0.2 M, pH 8, and 60 °C. A remarkable 96.2 and 93.2% of the total Pd was successfully extracted from the solid at 5% pulp density using both commercially available and biogenic thiosulfate, highlighting the method's versatility for Pd bioleaching from both thiosulfate sources.

A new sulfur bioconversion process development for energy- and space-efficient secondary wastewater treatment

Harvesting organic matter from wastewater, chemical enhanced primary treatment for instance, is widely applied to maximize energy recovery; however, it limits the applicability of secondary treatment for acceptable effluent discharge into surface water bodies. To turn this bottleneck issue into an opportunity, this study developed oxygen-induced thiosulfatE production duRing sulfATe reduction (ERATO) to provide efficient electron donor for denitrification or partial denitrification anammox in wastewater treatment. Typical pretreated wastewater was synthesized with chemical oxygen demand of 110 mg/L, sulfate of 50 mg S/L, ammonium of 30 mgN/L, and varying dissolved oxygen (DO) and was fed into a moving-bed biofilm reactor (MBBR) with a short hydraulic retention time of 40 min. The ORP maintained at − 311 mV in the bioreactor, indicating that the influent DO was vanished immediately when it enters the bioreactor. In 349 days’ continuous operation, the surface-specific sulfate reduction rate reached 0.42 g S/(m2·d). Notably, the formation rate of thiosulfate reached 0.12–0.18 g S/(m2·d) with a high thiosulfate-Sproduced/sulfide-Sproduced ratio of 38–73% when influent DO was 2.7–3.6 mg/L, much higher than 0–17% obtained in previously reported sulfate-reducing process. Then, batch tests and metabolism analysis were conducted to confirm the oxygen effect on thiosulfate formation, and to explore the mechanism of oxygen-induced thiosulfate formation in ERATO. Results examined that oxygen supply promoted the thiosulfate-Sproduced/sulfide-Sproduced ratio from 4% to 24–26%, demonstrated that S0 and sulfate were critical for thiosulfate production, and indicated that oxygen induces thiosulfate formation mainly through: sulfide first oxidized to S0 which then reacts with sulfite derived from oxygen-regulated biological sulfate reduction (S0 + SO32−→S2O32−). The proposed compact ERATO process with high thiosulfate production, supporting space- and energy-efficient secondary wastewater treatment.

Multifarious characteristics of sulfur-oxidizing bacteria residing in rice rhizosphere.

Sulfur-oxidizing bacteria (SOB) are versatile microorganisms known for their ability to oxidize various reduced sulfur compounds, namely, elemental sulfur (S0), hydrogen sulfide (H2S), tetrathionate (S4O62-), and trithionate (S3O62-) to sulfate (SO42-). In this study, out of twelve SOB isolates from rice rhizosphere, five were screened based on their sulfur oxidation potential, viz., SOB1, SOB2, SOB3, SOB4, and SOB5, and were identified as Ochrobactrum soli SOB1, Achromobacter xylosoxidans SOB2, Stenotrophomonas maltophilia SOB3, Brucella tritici SOB4, and Stenotrophomonas pavanii SOB5, respectively. All the isolates displayed chemolithotrophic nutritional mode by consuming thiosulfate and accumulating trithionate and tetrathionate in the growth medium which is ultimately oxidized to sulfate. The strains were authenticated with the production of thiosulfate oxidizing enzymes such as rhodanese and sulfite oxidase. Despite their tendency to oxidize reduced sulfur compounds, B. tritici SOB4 and S. pavanii SOB5 were also found to possess phosphate and zinc solubilization potential, acetic acid, and indole acetic acid (IAA) production and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. The presence of sulfanyl (R-SH) groups was noticed in the A. xylosoxidans SOB2. Elemental sulfur conversion into sulfate was noted in the S. maltophilia SOB3, and hydrogen sulfide conversion into sulfate was observed in the Ochromobacter soli SOB1. Sulfur oxidation potential coupled with beneficial properties of the isolates widen the knowledge on SOB.

Nitrogen and sulfur cycling driven by Campylobacterota in the sediment-water interface of deep-sea cold seep: a case in the South China Sea.

Chemoautotrophs within Campylobacterota, especially Sulfurovum and Sulfurimonas, are abundant in the seawater-sediment interface of the Formosa cold seep in the South China Sea. However, the in situ activity and function of Campylobacterota are unknown. In this study, the geochemical role of Campylobacterota in the Formosa cold seep was investigated with multiple means. Two members of Sulfurovum and Sulfurimonas were isolated for the first time from deep-sea cold seep. These isolates are new chemoautotrophic species that can use molecular hydrogen as an energy source and CO2 as a sole carbon source. Comparative genomics identified an important hydrogen-oxidizing cluster in Sulfurovum and Sulfurimonas. Metatranscriptomic analysis detected high expression of hydrogen-oxidizing gene in the RS, suggesting that H2 was likely an energy source in the cold seep. Genomic analysis indicated that the Sulfurovum and Sulfurimonas isolates possess a truncated sulfur-oxidizing system, and metatranscriptomic analysis revealed that Sulfurovum and Sulfurimonas with this genotype were active in the surface of RS and likely contributed to thiosulfate production. Furthermore, geochemical and in situ analyses revealed sharply decreased nitrate concentration in the sediment-water interface due to microbial consumption. Consistently, the denitrification genes of Sulfurimonas and Sulfurovum were highly expressed, suggesting an important contribution of these bacteria to nitrogen cycling. Overall, this study demonstrated that Campylobacterota played a significant role in the cycling of nitrogen and sulfur in a deep-sea cold seep. IMPORTANCE Chemoautotrophs within Campylobacterota, in particular Sulfurovum and Sulfurimonas, are ubiquitous in deep-sea cold seeps and hydrothermal vents. However, to date, no Sulfurovum or Sulfurimonas has been isolated from cold seeps, and the ecological roles of these bacteria in cold seeps remain to be investigated. In this study, we obtained two isolates of Sulfurovum and Sulfurimonas from Formosa cold seep, South China Sea. Comparative genomics, metatranscriptomics, geochemical analysis, and in situ experimental study indicated collectively that Campylobacterota played a significant part in nitrogen and sulfur cycling in cold seep and was the cause of thiosulfate accumulation and sharp reduction of nitrate level in the sediment-water interface. The findings of this study promoted our understanding of the in situ function and ecological role of deep-sea Campylobacterota.

Improvement of gold bioleaching extraction from waste telecommunication printed circuit boards using biogenic thiosulfate by Acidithiobacillus thiooxidans

Cyanide usage in gold processing techniques has become increasingly challenging due to its toxicity and environmental impact. It is possible to develop environmentally friendly technology using thiosulfate because of its nontoxic characteristics. Thiosulfate production requires high temperatures, resulting in high greenhouse gas emissions and energy consumption. The biogenesized thiosulfate is an unstable intermediate product of Acidithiobacillus thiooxidans sulfur oxidation pathway to sulfate. A novel eco-friendly method was presented in this study to treat spent printed circuit boards (STPCBs) using biogenesized thiosulfate (Bio-Thio) obtained from Acidithiobacillus thiooxidans cultured medium. To obtain a preferable concentration of thiosulfate among other metabolites by limiting thiosulfate oxidation, optimal concentrations of inhibitor (NaN3: 3.25 mg/L) and pH adjustments (pH= 6–7) were found to be effective. Selection of the optimal conditions has led to the highest bio-production of thiosulfate (500 mg/L). The impact of STPCBs content, ammonia, ethylenediaminetetraacetic acid (EDTA), and leaching time on Cu bio-dissolution and gold bio-extraction were investigated using enriched-thiosulfate spent medium. The suitable conditions were a pulp density of 5 g/L, an ammonia concentration of 1 M, and a leaching time of 36 h, which led to the highest selective extraction of gold (65 ± 0.78%).

Biogenic Production of Thiosulfate from Organic and Inorganic Sulfur Substrates for Application to Gold Leaching

Gold mining and processing is an activity with large environmental impact due to the low concentration of gold in ore deposits and chemical resistance to most chemicals. Over 75% of gold is leached from ores using cyanide, however less toxic lixiviants have been proposed in the literature. Thiosulfate is one of these alternative reagents, but high reagent consumption has slowed acceptance in mining operations. Reducing the cost and impact of thiosulfate production is a way to reduce the cost of reagent consumption during leaching. The objective of this study was to evaluate the feasibility of leaching gold from ore with biogenic thiosulfate. Biogenic thiosulfate was produced using a marine methylotroph bacterium from three substrates: sodium sulfide, elemental sulfur, and dimethyl sulfide for application in bioleaching. The different substrates were evaluated to determine conversion efficiency from the sulfur source to biogenic thiosulfate and verified by titration and ion chromatography. Optimal conditions for conversion to thiosulfate were determined to be in the range of pH = 7–8, 25–30 °C, with sodium sulfide as a substrate in a sealed system to prevent sulfide from escaping as hydrogen sulfide gas. An oxide gold ore with a grade of 4.02 g/t was selected as a gold source for leaching experiments. The leaching of gold using the biogenic thiosulfate was compared with chemical thiosulfate solutions under experimental conditions of pH = 9.5, 50 mg/L copper, 500 RPM mixing, and 0.1 L/min air. The efficiency of gold bioleaching was measured using flame atomic absorption spectroscopy and fire assay. Gold extraction efficiencies ranging from 20–60% were achieved using the biogenic thiosulfate, and 27–77% with sodium thiosulfate solutions, respectively. It was concluded that the sodium sulfide substrate was best for producing higher biogenic thiosulfate concentrations and leaching efficiency.

Variability in Background Urinary Concentrations of the Hydrogen Sulfide Biomarker Thiosulfate.

Hydrogen sulfide is a toxic gas at high concentrations but has recently attracted attention as a naturally produced gaseous signaling molecule in various tissues of the human body, playing key physiological roles at low nanomolar concentrations. This has wide implications for chronic exposure to this gas in air at low levels far below toxicity. Thiosulfate is the currently used biomarker for exposure to hydrogen sulfide via inhalation but has been mainly employed for acute exposure. It is unknown how background thiosulfate concentrations vary on an intraindividual and interindividual basis in humans at normal ambient hydrogen sulfide levels (<1 μg m-3), which is key for the interpretation of its levels as biomarker for low-level hydrogen sulfide exposure. In the current work, the variability in thiosulfate urinary excretion in a total of 168 urine samples collected from eight volunteers over a period of 8 weeks was investigated. The determination of thiosulfate in urine was carried out by UHPLC-MS/MS. The total average concentration ± SD was 16 ± 6 μM (n = 168). Average urinary thiosulfate concentrations in the studied volunteers were within the range of 10-20 μM, but it was found that urinary thiosulfate can show significant day-to-day and week-to-week variability in some individuals (up to 10-fold), despite adjusting for urine specific gravity. In light of the presented variability data and previous studies about the lack of consistent response of thiosulfate to low levels of hydrogen sulfide inhalation exposure, and based on a review of the biochemistry of the production of thiosulfate and its various biological sources, it can be argued that thiosulfate might not be suitable as a biomarker for chronic environmental exposure to low levels of hydrogen sulfide via inhalation.

Rhodaneses minimize the accumulation of cellular sulfane sulfur to avoid disulfide stress during sulfide oxidation in bacteria

Heterotrophic bacteria and human mitochondria often use sulfide: quinone oxidoreductase (SQR) and persulfide dioxygenase (PDO) to oxidize sulfide to sulfite and thiosulfate. Bioinformatic analysis showed that the genes encoding RHOD domains were widely presented in annotated sqr-pdo operons and grouped into three types: fused with an SQR domain, fused with a PDO domain, and dissociated proteins. Biochemical evidence suggests that RHODs facilitate the formation of thiosulfate and promote the reaction between inorganic polysulfide and glutathione to produce glutathione polysulfide. However, the physiological roles of RHODs during sulfide oxidation by SQR and PDO could only be tested in an RHOD-free host. To test this, 8 genes encoding RHOD domains in Escherichia coli MG1655 were deleted to produce E. coli RHOD-8K. The sqrCp and pdoCp genes from Cupriavidus pinatubonensis JMP134 were cloned into E. coli RHOD-8K. SQRCp contains a fused RHOD domain at the N-terminus. When the fused RHOD domain of SQRCp was inactivated, the cells oxidized sulfide into increased thiosulfate with the accumulation of cellular sulfane sulfur in comparison with cells containing the intact sqrCp and pdoCp. The complementation of dissociated DUF442 minimized the accumulation of cellular sulfane sulfur and reduced the production of thiosulfate. Further analysis showed that the fused DUF442 domain modulated the activity of SQRCp and prevented it from directly passing the produced sulfane sulfur to GSH. Whereas, the dissociated DUF442 enhanced the PDOCp activity by several folds. Both DUF442 forms minimized the accumulation of cellular sulfane sulfur, which spontaneously reacted with GSH to produce GSSG, causing disulfide stress during sulfide oxidation. Thus, RHODs may play multiple roles during sulfide oxidation.

Coenzyme Q10 and related quinones oxidize H2S to polysulfides and thiosulfate

In the canonical pathway for mitochondrial H2S oxidation electrons are transferred from sulfide:quinone oxidoreductase (SQR) to complex III via ubiquinone (CoQ10). We previously observed that a number of quinones directly oxidize H2S and we hypothesize that CoQ10 may have similar properties. Here we examine H2S oxidation by CoQ10 and more hydrophilic, truncated forms, CoQ1 and CoQ0, in buffer using H2S and polysulfide fluorophores (AzMC and SSP4), silver nanoparticles to measure thiosulfate (H2S2O3), mass spectrometry to identify polysulfides and O2-sensitive optodes to measure O2 consumption. We show that all three quinones concentration-dependently catalyze the oxidization of H2S to polysulfides and thiosulfate in buffer with the potency CoQ0>CoQ1>CoQ10 and that CoQ0 specifically oxidizes H2S to per-polysulfides, H2S2,3,4. These reactions consume and require oxygen and are augmented by addition of SOD suggesting that the quinones, not superoxide, oxidize H2S. Related quinones, MitoQ, menadione and idebenone, oxidize H2S in similar reactions. Exogenous CoQ0 decreases cellular H2S and increases polysulfides and thiosulfate production and this is also O2-dependent, suggesting that the quinone has similar effects on sulfur metabolism in cells. Collectively, these results suggest an additional endogenous mechanism for H2S metabolism and a potential therapeutic approach in H2S-related metabolic disorders.

Metabolism of Sulfur-Containing Amino Acids: How the Body Copes with Excess Methionine, Cysteine, and Sulfide

Metabolism of excess methionine (Met) to homocysteine (Hcy) by transmethylation is facilitated by the expression of methionine adenosyltransferase (MAT) I/III and glycine N-methyltransferase (GNMT) in liver, and a lack of either enzyme results in hypermethioninemia despite normal concentrations of MATII and methyltransferases other than GNMT. The further metabolism of Hcy by the transsulfuration pathway is facilitated by activation of cystathionine β-synthase (CBS) by S-adenosylmethionine (SAM) as well as the relatively high KM of CBS for Hcy. Transmethylation plus transsulfuration effects catabolism of the Met molecule along with transfer of the sulfur atom of Met to serine to synthesize cysteine (Cys). Oxidation and excretion of Met sulfur depend upon Cys catabolism and sulfur oxidation pathways. Excess Cys is oxidized by cysteine dioxygenase 1 (CDO1) and further metabolized to taurine or sulfate. Some Cys is normally metabolized by desulfhydration pathways, and the hydrogen sulfide (H2S) produced is further oxidized to sulfate. If Cys or Hcy concentrations are elevated, Cys or Hcy desulfhydration can result in excess H2S and thiosulfate production. Excess Cys or Met may also promote their limited metabolism by transamination pathways.

Lithoautotrophical oxidation of elemental sulfur by fungi including Fusarium solani isolated from sandstone Angkor temples

Previous study about Fusarium solani THIF01, isolated from deteriorated sandstones of Angkor Wat, Cambodia, has suggested that this fungal strain harbored an endobacterium Bradyrhizobium sp. and oxidized elemental sulfur (S0) in carbon-free media. Here we eliminated the endobacterium in THIF01 and confirmed that the cured THIF01 retained the ability of chemolithoautotrophic growth on S0. In addition, thirteen out of eighteen identified fungal strains formed clearing zone on the agarose-solidified basal salts medium containing S0. F. solani f.sp. pisi NBRC9425 grew in carbon-free liquid medium oxidizing S0 to thiosulfate and sulfate. Furthermore, we proved that various fungi were capable of growth chemolithotrophically on S0. An addition of up to 15 mg l−1 of yeast extract to mineral-salts medium containing S0 enhanced the production of thiosulfate and sulfate, and higher concentration of yeast extract shifted the metabolism from chemolithotroph to chemoorganotroph. Fungal hyphae were observed to attach to the S0 granules when growing with less than 100 mg l−1 yeast extract in the medium, but no such association was evident when incubated with 200 mg l−1 or more yeast extract. Glucose at concentrations of up to 1 mg l−1 did not show any negative effect on the sulfur oxidation, indicating there was a threshold concentration of organic compounds affecting the chemolithotrophic growth that has been observed before in the chemolithoautotrophic and chemolithomixotrophic sulfur oxidizing bacteria.

The Role of Hemoproteins: Hemoglobin, Myoglobin and Neuroglobin in Endogenous Thiosulfate Production Processes.

Thiosulfate formation and biodegradation processes link aerobic and anaerobic metabolism of cysteine. In these reactions, sulfite formed from thiosulfate is oxidized to sulfate while hydrogen sulfide is transformed into thiosulfate. These processes occurring mostly in mitochondria are described as a canonical hydrogen sulfide oxidation pathway. In this review, we discuss the current state of knowledge on the interactions between hydrogen sulfide and hemoglobin, myoglobin and neuroglobin and postulate that thiosulfate is a metabolically important product of this processes. Hydrogen sulfide oxidation by ferric hemoglobin, myoglobin and neuroglobin has been defined as a non-canonical hydrogen sulfide oxidation pathway. Until recently, it appeared that the goal of thiosulfate production was to delay irreversible oxidation of hydrogen sulfide to sulfate excreted in urine; while thiosulfate itself was only an intermediate, transient metabolite on the hydrogen sulfide oxidation pathway. In the light of data presented in this paper, it seems that thiosulfate is a molecule that plays a prominent role in the human body. Thus, we hope that all these findings will encourage further studies on the role of hemoproteins in the formation of this undoubtedly fascinating molecule and on the mechanisms responsible for its biological activity in the human body.

Investigation of transient forms of sulfur during biological treatment of spent caustic

ABSTRACTIn the present study, the production of various transient forms of sulfur during biological oxidation of sulfidic spent caustics under haloalkaline conditions in a stirred tank bioreactor is investigated. Also, the effects of abiotic aeration (chemical oxidation), dissolved oxygen (DO) concentration and sodium concentration on forms of sulfur during biological treatment are demonstrated. Thioalkalivibrio versutus strain was used for sulfide oxidation in spent caustic (SC). The aeration had an important effect on sulfide oxidation and its final products. At DO concentrations above 2 mg l−1, majority of sulfide was oxidized to sulfate. Maximum sulfide removal efficiency (%R) and yield of sulfate production was obtained in Na+ concentration ranging from 0.6 to 2 M. Abiotic aeration, which is the most important factor of production of thiosulfate, resulted in the formation of an undesired product-polysulfide. However, abiotic aeration can be used as a pretreatment to biological treatment. In the bioreactor the removal efficiency was obtained as 82.7% and various forms of sulfur such as polysulfide, biosulfur, thiosulfate and sulfate was observed during biological treatment of SC.

Chemolithoheterotrophy in a metazoan tissue: thiosulfate production matches ATP demand in ciliated mussel gills.

The ribbed mussel Geukensia demissa inhabits sulfide-rich coastal sediments with a distribution that suggests a preference for exposure to sulfide. Although sulfide is a respiratory poison, it is also a potent reductant. Geukensia demissa gill mitochondria can use sulfide as a respiratory substrate for ATP production, and the gills of this species exhibit sulfide-supported oxygen consumption that matches the energy demand of ciliary beating. Here, we demonstrate (i) that the major product of G. demissa gill sulfide oxidation is thiosulfate and (ii) that the rate of sulfide oxidation also matches the cellular energy demand, resulting in a ratio near unity of oxygen consumed to sulfide oxidized at both low and high ciliary beat frequencies. A value for this ratio of unity is consistent with electrons from sulfide oxidation entering the mitochondrial electron transport chain. In the gills of the blue mussel Mytilus edulis from sulfide-free conditions, this ratio is 3-5 times higher, indicating an uncoupling of oxygen consumption from sulfide oxidation. Whereas M. edulis gills exhibit anaerobic metabolism during sulfide exposure, G. demissa gills do not, indicating a difference in sulfide tolerance between the two mussel species.

Oxidation of hydrogen sulfide and methanethiol to thiosulfate by rat tissues: a specialized function of the colonic mucosa

Colonic bacteria release large quantities of the highly toxic thiols hydrogen sulfide (H 2S) and methanethiol (CH 3SH). These gases rapidly permeate the colonic mucosa, and tissue damage would be expected if the mucosa could not detoxify these compounds rapidly. We previously showed that rat cecal mucosa metabolizes these thiols via conversion to thiosulfate. The purpose of the present study in rats was to determine if this conversion of thiols to thiosulfate is (a) a generalized function of many tissues, or (b) a specialized function of the colonic mucosa. The tissues studied were mucosa from the cecum, right colon, mid-colon, ileum, and stomach; liver; muscle; erythrocytes; and plasma. The metabolic rate was determined by incubating homogenates of the various tissues with H 2 35S and CH 3 35SH and measuring the rate of incorporation of 35S into thiosulfate and sulfate. The detoxification activity of H 2S (expressed as nmol/mg per min) that resulted in thiosulfate production was at least eight times greater for cecal and right colonic mucosa than for the non-colonic tissues. Thiosulfate production from CH 3SH was at least five times more rapid for cecal and right colonic mucosa than for the non-colonic tissues. We conclude that colonic mucosa possesses a specialized detoxification system that allows this tissue to rapidly metabolize H 2S and CH 3SH to thiosulfate. Presumably, this highly developed system protects the colon from what otherwise might be injurious concentrations of H 2S and CH 3SH. Defects in this detoxification pathway possibly could play a role in the pathogenesis of various forms of colitis.

Electrosynthesis of Sodium Hydrosulfite: II. The Effect of Cathode Material

Sodium hydrosulfite is a major commodity reagent currently manufactured mainly by chemical means. A new, lower cost, electrochemical pathway is being used in some cases. One of the key determinants in the marketability of sodium hydrosulfite is the level of sodium thiosulfate in the product. At present, the level of thiosulfate from the electrochemical process is higher than that from the chemical process. Here a critical evaluation is presented of cathode materials for the electrochemical manufacture of sodium hydrosulfite nearly devoid of thiosulfate. It is demonstrated that the yield, selectivity, and efficiency of hydrosulfite and thiosulfate production depends upon the applied potential, pH of the feedstream, buffering capacity, and cathode material. Several planar cathodes for the electrosynthesis of hydrosulfite have been critically evaluated. We demonstrate that five main process parameters contribute to high hydrosulfite to thiosulfate ratios; reactant concentration, feedstream pH, buffer capacity, cathode material, and applied potential. By control of these parameters, we demonstrate that hydrosulfite solutions devoid of thiosulfate can be electrochemically produced.

Mitochondrial sulfide oxidation in Arenicola marina. Evidence for alternative electron pathways.

Sulfide is oxidized in the mitochondria of the lugworm Arenicola marina. Mitochondrial sulfide oxidation is coupled with oxygen consumption and with an equimolar production of thiosulfate [Völkel, S. & Grieshaber, M. K. (1994) Mar. Biol. 118, 137-147]. Mitochondrial respiration in the presence of malate (or succinate) and ADP but without sulfide could be completely inhibited by rotenone, antimycin, cyanide, and sulfide. Only 40% inhibition was achieved by salicylhydroxamic acid. Sulfide oxidation (with sulfide as the only substrate) was fully inhibited by antimycin and by salicylhydroxamic acid but not by rotenone or sulfide. Moreover, sulfide oxidation was 3-4-fold less sensitive to cyanide as compared to normal respiration. The data indicate that sulfide oxidation in A. marina is linked to the respiratory electron transport chain. We suggest that electrons from sulfide enter the respiratory chain via ubiquinone or at the ubiquinol-cytochrome-c oxidoreductase. At sulfide concentrations higher than 10 microM, the cytochrome-c oxidase is blocked and electrons from sulfide are transferred to oxygen via an alternative terminal oxidase.

Crystal Structures of Two New Complexes Produced by Reaction of Copper(I) Cyanide with Thioacetamide. In Situ Formation of the Thiosulfate Anion

An attempt to synthesize a complex between copper(I) cyanide and thioacetamide (ta) by a direct combination in aqueous solution, surprisingly, produced instead Cu(4)(S(2)O(3))(2)(ta)(10).ta (1), a complex lacking cyanide but including thiosulfate. We know of no precedent for the production of thiosulfate from an aqueous solution of ta. Using a new synthetic approach, a complex of CuCN and ta was subsequently prepared-(CuCN)(ta), 2. In the new method, which has been found to be widely applicable to water-soluble ligands, CuCN is made "available" for coordination by dissolving it in aqueous sodium thiosulfate. Complex 1 crystallizes in the triclinic space group P&onemacr; (No. 2) with unit cell dimensions a = 10.139(3) Å, b = 12.230(4) Å, c = 12.665(4) Å, alpha = 85.20(2) degrees, beta = 67.32(2) degrees, gamma = 68.47(2) degrees, V = 1345(2) Å(3), and Z = 2. Complex 2 crystallizes in the orthorhombic space group Pna2(1) (No. 33) with unit cell dimensions a = 6.993(9) Å, b = 8.744(3) Å, c = 9.372(6) Å, V = 573(1) Å(3), and Z = 4. Some possible pathways for the production of thiosulfate are discussed.

Thiosulfate Production in Cysteine‐Amended Soil

AbstractThiol‐labile compounds are produced in cysteine‐amended soil, as evidenced by the production of H2S following addition of reagents containing free sulfhydryl groups (−SH). Thiosulfate (S2O2−3) is a likely reactant candidate because it is an intermediate in biogeochemical S cycling and is reduced to H2S by ‐SH, but its presence in cysteine‐amended soils has not been documented previously. Four soils were amended with l‐cysteine (15 mmol kg−1 soil) incubated at 0.033 MPa soil water suction or under saturated conditions, and then extracted with 0.1 M LiCl. Colorimetric analysis of the extracts using cyanolysis with and without addition of a Cu2+ catalyst indicated the presence of S22−3 and a polythionate such as S4O2−6; positive interferences from the cyanolysis of S2− were minimal. Ion chromatographic analysis of the extracts showed a well‐resolved peak with the same retention time as S2O2−3 and yielded concentration estimates similar to those obtained by colorimetry, providing positive identification of S2O2−3 in cysteine‐amended soils. Thiosulfate production occurred under both saturated and unsaturated conditions, varied among soils from 0 to 35.2 mg S2O2−3‐S kg−1, and was nearly eliminated by autoclaving the soil before incubation or by addition of NaN3. Although the exact pathway for S2O2−3 production is unknown, it is likely that H2S formation and subsequent oxidation are responsible.

Oxygen dependent sulfide detoxification in the lugwormArenicola marina

The lugwormArenicola marina L. oxidizes entering sulfide to thiosulfate. After 8 h of normoxic incubations with sulfide concentrations of 0.2 to 1.0 mmoll-1 thiosulfate in the coelomic fluid amounted up to about 4 mmoll-1 whereas sulfite concentrations were 100-fold lower and no accumulation of sulfate in the coelomic fluid was found. The sulfide oxidation was highly oxygen dependent. An increase of oxygen partial pressure (\(P_{O_2 }\)) in the medium was followed by enhanced thiosulfate production and by a decrease of sulfide concentration in the coelomic fluid. Under normoxia, the sulfide oxidation rate was sufficient to compensate the influx of sulfide into the coelomic fluid when the sulfide concentration in the medium was below 0.33 mmoll-1. When external sulfide was raised beyond this level, sulfide up to 5 μmoll-1 in the coelomic fluid appeared. Succinate in the body wall tissue was low as long as no sulfide appeared in the coelomic fluid, indicating the maintenance of an aerobic metabolism. The oxidation of sulfide to thiosulfate was localized in the mitochondria of the body wall tissue. The oxygen consumption of mitochondria was stimulated by the addition of sulfide. The mitochondrial sulfide oxidation rate depended on the amount of mitochondrial protein and followed a Michaelis-Menten kinetic. An apparentKm of 0.68±0.29 μmoll-1 and aVmax of 41.9±22.3 nmol min-1 mg-1 protein was calculated. Sulfide was stoichiometrically oxidized to thiosulfate with 1 mol sulfide consuming 1 mol oxygen. Sulfide oxidation was not inhibited by sulfide concentrations as high as 100 μmoll-1. At low concentrations of cyanide or azide, when respiration without sulfide was already inhibited, sulfide oxidation could still be stimulated, tentatively indicating the existence of an alternative terminal oxidase. Specimens examined in the present study were collected near St. Pol de Leon, France, from 1989 to 1992.