Sulfide Source Research Articles

Structure-based identification of potential substrate antagonists for isethionate sulfite-lyase enzyme of Bilophila Wadsworthia: Towards novel therapeutic intervention to curb gut-associated illness

Bilophila wadsworthia is one of the prominent sources of hydrogen sulfide (H2S) production in appendices, excessive levels of which can result in a weaker colonic mucus barrier, inflammatory bowel disease, and colorectal cancer. Isethionate sulfite-lyase (IslA) enzyme catalyzes H2S production by cleaving CS bond in isethionate, producing acetaldehyde and sulfite. In this study, we aimed to identify potential substrate antagonists for IsIA using a structure-based drug design. Initially, pharmacophore-based computational screening of the ZINC20 database yielded 66 hits that were subjected to molecular docking targeting the isethionate binding site of IsIA. Based on striking docking scores, nine compounds showed strong interaction with critical IsIA residues (Arg189, Gln193, Glu470, Cys468, and Arg678), drug-like features, appropriate adsorption, metabolism, excretion, and excretion profile with non-toxicity. Molecular dynamics simulations uncovered the significant impact of binding the compounds on protein conformational dynamics. Finally, binding free energies revealed substantial binding affinity (ranging from −35.23 to −53.88 kcal/mol) of compounds (ZINC913876497, ZINC913856647, ZINC914263733, ZINC914137795, ZINC915757996, ZINC914357083, ZINC913934833, ZINC9143362047, and ZINC913854740) for IsIA. The compounds proposed herein through a multi-faceted computational strategy can be experimentally validated as potential substrate antagonists of B. wadsworthia's IsIA for developing new medications to curb gut-associated illness in the future.

Role of Cystathionine β-Synthase and 3-Mercaptopyruvate Sulfurtransferase in the Regulation of Proliferation, Migration, and Bioenergetics of Murine Breast Cancer Cells

Cystathionine β-synthase (CBS), CSE (cystathionine γ-lyase) and 3-mercaptopyruvate sulfurtransferase (3-MST) have emerged as three significant sources of hydrogen sulfide (H2S) in various forms of mammalian cancer. Here, we investigated the functional role of CBS' and 3-MST's catalytic activity in the murine breast cancer cell line EO771. The CBS/CSE inhibitor aminooxyacetic acid (AOAA) and the 3-MST inhibitor 2-[(4-hydroxy-6-methylpyrimidin-2-yl)sulfanyl]-1-(naphthalen-1-yl)ethan-1-one (HMPSNE) were used to assess the role of endogenous H2S in the modulation of breast cancer cell proliferation, migration, bioenergetics and viability in vitro. Methods included measurements of cell viability (MTT and LDH assays), cell proliferation and in vitro wound healing (IncuCyte) and cellular bioenergetics (Seahorse extracellular flux analysis). CBS and 3-MST, as well as expression were detected by Western blotting; H2S production was measured by the fluorescent dye AzMC. The results show that EO771 cells express CBS, CSE and 3-MST protein, as well as several enzymes involved in H2S degradation (SQR, TST, and ETHE1). Pharmacological inhibition of CBS or 3-MST inhibited H2S production, suppressed cellular bioenergetics and attenuated cell proliferation. Cell migration was only inhibited by the 3-MST inhibitor, but not the CBS/CSE inhibitor. Inhibition of CBS/CSE of 3-MST did not significantly affect basal cell viability; inhibition of 3-MST (but not of CBS/CSE) slightly enhanced the cytotoxic effects of oxidative stress (hydrogen peroxide challenge). From these findings, we conclude that endogenous H2S, generated by 3-MST and to a lower degree by CBS/CSE, significantly contributes to the maintenance of bioenergetics, proliferation and migration in murine breast cancer cells and may also exert a minor role as a cytoprotectant.

Experimental study of mass transfer by volatilization inside a portable wind tunnel used to estimate emission rates for odorous compounds

Wastewater treatment plants are sources of hydrogen sulfide in urban environments. This compound, at certain concentrations, may be associated with compromising the health and well-being of populations living near such sources, characterized by diffuse emission, which makes it difficult to quantify. The portable wind tunnel is one of the devices used to measure this type of emission; however, this equipment is not capable of simulating all significant mass transport phenomena. Thus, this study investigated mass transfer at the liquid-gas interface of hydrogen sulfide by estimating the global mass transfer coefficient within the portable wind tunnel. The inlet flow rate into the system ranged from 600 to 1,800 , and the analysis of concentration decay in the liquid phase was performed using spectrophotometry. The observed exponential decay is consistent with the adopted hypotheses; however, no significant variation in the mass transfer coefficient was observed for different system operation flow rates. The average value found was 2.70×10 -5 ±2.99×10 -6 . In summary, this study contributed to understanding the mass transfer of hydrogen sulfide in wastewater treatment environments using a portable wind tunnel as an experimental tool.

Increased oceanic dimethyl sulfide emissions in areas of sea ice retreat inferred from a Greenland ice core

Ocean phytoplankton are an important source of dimethyl sulfide, which influences marine cloud formation. Model studies suggest that declines in Arctic sea ice may lead to increased dimethyl sulfide emissions, however observational support is lacking. Here, we present a 55-year high-resolution ice core record of methane sulfonic acid flux, an oxidation product of dimethyl sulfide, from the southeast Greenland Ice Sheet. We infer temporal variations in ocean dimethyl sulfide emissions and find that springtime (April–June) fluxes of methane sulfonic acid correlate well with satellite-derived chlorophyll-a concentration in the Irminger Sea. Summertime (July–September) methane sulfonic acid fluxes were 3 to 6 times higher between 2002–2014 than 1972–2001. We attribute this to sea ice retreat day becoming earlier and a coincident increase in chlorophyll-a concentration in the adjacent open coastal waters.

Effect of sulfide and hydroxide on the removal of heavy metal ions from hydrometallurgical zinc effluent

ABSTRACT Heavy metals removal from Specialized Industrial Park of Zinc of Zanjan effluent was tested using sulfide, hydroxide, and the combination precipitation. The initial effluent includes 200 ppm of zinc, 55 ppm of cadmium, 113 ppm of manganese, 0.85 ppm cobalt, 0.65 ppm nickel, 0.2 ppm iron, and 0.55 ppm lead. Sulfide precipitation using Na2S as a sulfide source is inefficient in the precipitation of manganese except in high concentrations of sulfide, while hydroxide precipitation using lime is not successful in cadmium removal. Combining these two methods in one and two steps is helpful in the precipitation and settling of all heavy metal ions. The optimum temperature, pH, sulfide concentration, and time were determined. The concentration of zinc, cadmium, manganese, cobalt, nickel, and iron were reduced to 0.1, 0.1, 0.14, 0.23, 0.19, and 0.16 ppm, while lead was not detected in the solution in optimum condition. The experiments were repeated for effluent with higher amounts of lead, iron, and nickel, and its success in efficient removing of these ions is also confirmed. Scanning electron microscope (SEM) images and X-ray diffraction (XRD) patterns were used to study morphologies and structures of precipitation. The concentration of Na2S plays a crucial role in removal efficiency. Excess sulfide causes the increment of ions such as manganese in the solution and decrements the efficiency discussed in this research. The lower use of lime, almost no excess sulfide ions in solution, fast kinetics, and precipitating of a wide range of metal ions are some advantages of this method.

Oxidative Stress Regulates a Pivotal Metabolic Switch in Dimethylsulfoniopropionate Degradation by the Marine Bacterium Ruegeria pomeroyi.

Dimethylsulfoniopropionate (DMSP) is an abundant organic compound in marine surface water and source of dimethyl sulfide (DMS), the largest natural sulfur source to the upper atmosphere. Marine bacteria either mineralize DMSP through the demethylation pathway or transform it to DMS through the cleavage pathway. Factors that regulate which pathway is utilized are not fully understood. In chemostat experiments, the marine Roseobacter Ruegeria pomeroyi DSS-3 was exposed to oxidative stress either during growth with H2O2 or by mutation of the gene encoding catalase. Oxidative stress reduced expression of the genes in the demethylation pathway and increased expression of those encoding the cleavage pathway. These results are contrary to the sulfur demand hypothesis, which theorizes that DMSP metabolism is driven by sulfur requirements of bacterial cells. Instead, we find strong evidence consistent with oxidative stress control over the switch in DMSP metabolism from demethylation to DMS production in an ecologically relevant marine bacterium. IMPORTANCE Dimethylsulfoniopropionate (DMSP) is the most abundant low-molecular-weight organic compound in marine surface water and source of dimethyl sulfide (DMS), a climatically active gas that connects the marine and terrestrial sulfur cycles. Marine bacteria are the major DMSP consumers, either generating DMS or consuming DMSP as a source of reduced carbon and sulfur. However, the factors regulating the DMSP catabolism in bacteria are not well understood. Marine bacteria are also exposed to oxidative stress. RNA sequencing (RNA-seq) experiments showed that oxidative stress induced in the laboratory reduced expression of the genes encoding the consumption of DMSP via the demethylation pathway and increased the expression of genes encoding DMS production via the cleavage pathway in the marine bacterium Ruegeria pomeroyi. These results support a model where DMS production in the ocean is regulated in part by oxidative stress.

Spatial and diel patterns of volatile organic compounds, DMSP-derived compounds, and planktonic microorganisms around a tropical scleractinian coral colony

Volatile organic compounds (VOCs) are constituents of marine ecosystems including coral reefs, where they are sources of atmospheric reactivity, indicators of ecosystem state, components of defense strategies, and infochemicals. Most VOCs result from sunlight-related processes; however, their light-driven dynamics are still poorly understood. We studied the spatial variability of a suite of VOCs, including dimethylsulfide (DMS), and the other dimethylsulfoniopropionate-derived compounds (DMSPCs), namely, DMSP, acrylate, and dimethylsulfoxide (DMSO), in waters around colonies of two scleractinian corals (Acropora pulchra and Pocillopora sp.) and the brown seaweed Turbinaria ornata in Mo’orean reefs, French Polynesia. Concentration gradients indicated that the corals were sources of DMSPCs, but less or null sources of VOCs other than DMS, while the seaweed was a source of DMSPCs, carbonyl sulfide (COS), and poly-halomethanes. A focused study was conducted around an A. pulchra colony where VOC and DMSPC concentrations and free-living microorganism abundances were monitored every 6 h over 30 h. DMSPC concentrations near the polyps paralleled sunlight intensity, with large diurnal increases and nocturnal decrease. rDNA metabarcoding and metagenomics allowed the determination of microbial diversity and the relative abundance of target functional genes. Seawater near coral polyps was enriched in DMS as the only VOC, plus DMSP, acrylate, and DMSO, with a large increase during the day, coinciding with high abundances of symbiodiniacean sequences. Only 10 cm below, near the coral skeleton colonized by a turf alga, DMSPC concentrations were much lower and the microbial community was significantly different. Two meters down current from the coral, DMSPCs decreased further and the microbial community was more similar to that near the polyps than that near the turf alga. Several DMSP cycling genes were enriched in near-polyp with respect to down-current waters, namely, the eukaryotic DMS production and DMS oxidation encoding genes, attributed to the coral and the algal symbiont, and the prokaryotic DMS production gene dddD, harbored by coral-associated Gammaproteobacteria. Our results suggest that solar radiation-induced oxidative stress caused the release of DMSPCs by the coral holobiont, either directly or through symbiont expulsion. Strong chemical and biological gradients occurred in the water between the coral branches, which we attribute to layered hydrodynamics.

Sodium thiosulfate, a source of hydrogen sulfide, stimulates endothelial cell proliferation and neovascularization.

Therapies to accelerate vascular repair are currently lacking. Pre-clinical studies suggest that hydrogen sulfide (H2S), an endogenous gasotransmitter, promotes angiogenesis. Here, we hypothesized that sodium thiosulfate (STS), a clinically relevant source of H2S, would stimulate angiogenesis and vascular repair. STS stimulated neovascularization in WT and LDLR receptor knockout mice following hindlimb ischemia as evidenced by increased leg perfusion assessed by laser Doppler imaging, and capillary density in the gastrocnemius muscle. STS also promoted VEGF-dependent angiogenesis in matrigel plugs in vivo and in the chorioallantoic membrane of chick embryos. In vitro, STS and NaHS stimulated human umbilical vein endothelial cell (HUVEC) migration and proliferation. Seahorse experiments further revealed that STS inhibited mitochondrial respiration and promoted glycolysis in HUVEC. The effect of STS on migration and proliferation was glycolysis-dependent. STS probably acts through metabolic reprogramming of endothelial cells toward a more proliferative glycolytic state. These findings may hold broad clinical implications for patients suffering from vascular occlusive diseases.

Anoxia-Related Biogeochemistry of North Indian Ocean

Complex interactions between microbial communities and geochemical processes drive the major element cycles and control the function of marine sediments as a dynamic reservoir of organic matter. Sulfate reduction is globally the dominant pathway of anaerobic mineralisation and is the main source of sulfide. The effective re-oxidation of this sulfide at the direct or indirect expense of oxygen is a prerequisite for aerobic life on our planet. Although largely hidden beneath the oxic sediment surface, the sulfur cycle is therefore critical for Earth’s redox state. This Geochemical Perspectives begins with a brief primer on the sulfur cycle of marine sediments and a description of my own scientific journey through nearly fifty years of studies of sulfur geochemistry and microbiology. Among the main objectives of these studies were to quantify the main processes of the sulfur cycle and to identify the microbial communities behind them. Radiotracers in combination with chemical analyses have thereby been used extensively for laboratory experiments, supported by diverse molecular microbiological methods. The following sections discuss the main processes of sulfate reduction, sulfide oxidation and disproportionation of the inorganic sulfur intermediates, especially of elemental sulfur and thiosulfate. The experimental approaches used enable the analysis of how environmental factors such as substrate concentration or temperature affect process rates and how concurrent processes of sulfate reduction and sulfide oxidation drive a cryptic sulfur cycle. The chemical energy of sulfide is used by chemolithotrophic bacteria, including fascinating communities of big sulfur bacteria and cable bacteria, and supports their dark CO2 fixation, which produces new microbial biomass. During the burial and aging of marine sediments, the predominant mineralisation processes change through a cascade of redox reactions, and the rate of organic matter degradation drops continuously over many orders of magnitude. The main pathways of anaerobic mineralisation and the age control of the organic matter turnover are discussed. In the deep methanic zone, only a few percent of the entire degradation process remains, which provides a small boost of substrate for sulfate reduction through the process of anaerobic methane oxidation. The stable isotopes of sulfur provide an additional tool to understand these diagenetic processes, whereby the combination of microbial isotope fractionation and open system diagenesis generate a differential diffusion flux of the isotopes. In relation to the organic carbon cycle of the seabed and the contribution of methane, the paper discusses the global sulfur budget and the role of sulfate reduction for organic matter mineralisation in different depth regions of the ocean - from coast to deep sea. The published estimates of these parameters are evaluated and compared. Finally, the paper looks at future perspectives with respect to gaps in our current understanding and the need for further studies.

Simultaneous use of nitrate and calcium peroxide to control sulfide and greenhouse gas emission in sewers

The sewer system is a significant source of hydrogen sulfide (H2S) and greenhouse gases which has attracted extensive interest from researchers. In this study, a novel combined dosing strategy using nitrate and calcium peroxide (CaO2) was proposed to simultaneously control sulfide and greenhouse gases, and its performance was evaluated in laboratory-scale reactors. Results suggested that the addition of nitrate and CaO2 improved the effectiveness of sulfide control. And the combination index method further proved that nitrate and CaO2 were synergistic in controlling sulfide. Meanwhile, the combination of nitrate and CaO2 substantially reduced greenhouse gas emissions, especially the carbon dioxide (CO2) and methane (CH4). The microbial analysis revealed that the combined addition greatly stimulated the accumulation of nitrate reducing-sulfide oxidizing bacteria (NR-SOB) that participate in anoxic nitrate-dependent sulfide oxidation, while the abundance of heterotrophic denitrification bacteria (hNRB) was reduced significantly. Moreover, the presence of oxygen and alkaline chemicals generated by CaO2 facilitated the inhibition of sulfate-reducing bacteria (SRB) activities. Therefore, the nitrate dosage was diminished significantly. On the other hand, the generated alkaline chemicals promoted CO2 elimination and inhibited the activities of methanogens, leading to a decrease of CO2 and CH4 fluxes, which facilitated elimination of greenhouse effects. The intermittent dosing test showed that the nitrate and CaO2 could be applied intermittently for sulfide removal. And the chemical cost of intermittent dosing strategy was reduced by 85 % compared to the continuous dosing nitrate strategy. Therefore, intermittent dosing nitrate combined with CaO2 is probably an effective and economical approach to control sulfide and greenhouse gases in sewer systems.

Mixed crustal-mantle source of porphyry Cu-Mo deposits of the Urals: Pyrite trace element geochemistry and Pb – S isotope data

Developing genetic models of porphyry Cu-, Mo-, and Cu-Mo deposits requires knowledge on the source of metals for these deposits. Even though porphyry Cu deposits worldwide were relatively well-studied and the corresponding sources of metals were considered, porphyry Cu-Mo deposits of the Urals were not previously investigated. The paper presents new data on two porphyry Cu-Mo deposits of Paleozoic age: namely Late Devonian to Early Carboniferous Verkhneuralskoe in the South Urals and Late Carboniferous to Early Permian Talitsa in the Middle Urals. Pyrite trace element data indicate minor input of Ni, Tl, and Ag from host rocks of the Talitsa deposit. Talitsa and Vekhneuralskoe deposits are heterogeneous in Pb isotope composition and, on the contrary, homogeneous in S isotope composition which is typical for porphyry deposits worldwide. The both deposits show similar age-corrected Pb isotope compositions of sulfides (18.228 to 18.521 for 206Pb/204Pb, 15.598 to 15.705 for 206Pb/204Pb, and 38.087 to 38.474 for 208Pb/204Pb) and of magmatic and hydrothermal K-feldspars (from 18.291 to 18.449 for 206Pb/204Pb, from 15.598 to 15.608 for 207Pb/204Pb, and from 38.023 to 38.127 for 208Pb/204Pb); δ34S varies from −0.4 to +3.4 ‰. The isotope data suggest that granitoid melts were the dominant source of both sulfides and ore-bearing magmatic rocks. Mantle-crustal mixing model calculated for the Urals shows 95 % of mantle Pb in porphyry Cu-Mo deposits.

Monitoring of hydrogen sulfide content in winter in the observation points of Atyrau city

The article analyzes the monitoring of hydrogen sulfide content in the air of Atyrau in the winter period of 2021-2022. The purpose of this study is to study the hydrogen sulfide content in the air environment of the city of Atyrau, which has been increasing in recent years as a result of anthropogenic impact. The monitoring results were analyzed according to the data of Kazhydromet observation points, including 15 observation points. Monitoring of the study showed that among 15 observation points, there are exceedances of the maximum permissible concentrations of hydrogen sulfide in all three winter months, but however, it can be observed that the highest concentrations are observed in December and February, whereas in January these data are close to the MPC. Especially high rates are characteristic of points located near the Atyrau Oil Refiner, which is probably the main source of hydrogen sulfide. At the same time, the excess of the MPC for hydrogen sulfide and at points in the territories of the city exceeds more than 5-15 times. An important step towards optimizing the monitoring of the effects of hydrogen sulfide emissions at the Atyrau Refinery is the monitoring of atmospheric air quality and the introduction of modern technologies and dust and gas cleaning equipment. At the same time, it is possible to reduce the emission of hydrogen sulfide as a result of measures aimed at the reconstruction and overhaul of the sewage system in Atyrau. Key words: hydrogen sulfide in the air, Atyrau, monitoring, winter period, Kazhydromet observation points.

Sulfate sources of thermochemical sulfate reduction and hydrogen sulfide distributions in the Permian Changxing and Triassic Feixianguan formations, Sichuan Basin, SW China

The sulfate sources of thermochemical sulfate reduction (TSR) and hydrogen sulfide (H2S) distributions in the Permian Changxing (P2c) and Triassic Feixianguan formations (T1f) in the Sichuan Basin were investigated using geochemical and carbon isotopic data for gases, and sulfur isotopic data for solid bitumen, H2S, and anhydrite. The concentration of H2S (>5.0%) is relatively high, and the δ34S values of the H2S are significantly higher than those of the Permian source rock kerogen, suggesting a TSR origin for the H2S. The δ13C values of the methane and ethane do not increase as the gas souring index (H2S/(H2S+∑Cn)) increases, and the δ34S values of the H2S are significantly lower than those of the solid bitumen, suggesting mainly liquid hydrocarbon dominated-TSR. The δ34S values of the solid bitumen and H2S in the Puguang gas field in the eastern platform are significantly lower than those in the Yuanba gas field in the western platform, and the sulfates for the TSR were most likely derived from the Early and Late T1f evaporative seawater, respectively. The sulfates required for TSR were most likely enriched during dolomitization based on the positive relationship between the H2S concentrations and the thickness of the dolostone reservoirs. The H2S distributions were mainly controlled by the sulfate distributions and the paleo-oil accumulations. The edges of the eastern and western platforms in the Kaijiang-Liangping trough, which were favorable for dolomitization and paleo-oil accumulations, are the most likely H2S-enriched areas in the Sichuan Basin.

In silico screening, molecular dynamic simulations, and in vitro activity of selected natural compounds as an inhibitor of Leishmania donovani 3-mercaptopyruvate sulfurtransferase.

In Leishmania sp., the enzymes of de novo cysteine biosynthesis pathway require sulfide. Other organisms utilize sulfide through the sulfide reduction pathway, but Leishmania lacks the gene that encodes these enzymes. Hence, the major source of sulfide for Leishmania is believed to be from the action of 3-mercaptopyruvate sulfurtransferase (3MST) on 3-mercapto-pyruvate (3MP). There has been no effort reported in the past to screen inhibitors against L. donovani 3MST (Ld3MST). As a result, this study examines natural compounds that are potent against Ld3MST and validates it by in vitro activity and cytotoxicity tests. Initially, a library of ~ 5000 natural compounds was subjected to molecular docking approach for screening, and the best hit was validated using a long-term molecular dynamic simulation (MD). Among the docking results, quercetine-3-rutinoside (Rutin) was deemed the best hit. The results of the MD indicated that Rutin was highly capable of interacting with the varied active site segments, possibly blocking substrate access. Additionally, promastigotes and amastigotes were tested for Rutin activity and the IC50 was found to be 40.95 and 90.09 μM, respectively. Similarly, the cytotoxicity assay revealed that Rutin was not toxic even at a concentration of 819.00 μM to THP-1 cell lines. Additionally, the Ld3MST was cloned, purified, and evaluated for enzyme activity in the presence of Rutin. Reduction in the enzyme activity (~ 85%) was observed in the presence of ~ 40 μM Rutin. Thus, this study suggests that Rutin may act as a potent inhibitor of Ld3MST. With further in vivo investigations, Rutin could be a small molecule of choice for combating leishmaniasis.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00436-022-07532-5.

Elaboration and characterization of cadmium sulfide (CdS) thin films prepared by chemical bath deposition (CBD)

The chemical bath deposition technique has found great success in recent years as it has become an integral part of the industrial process for the preparation of large-scale solar cells. In this work we have elaborated CdS thin films on glass substrates by the CBD chemical bath deposition technique from an aqueous solution containing CdCl2 and (NH2)2CS as sources of sulfide and cadmium ions for different deposition temperatures. The structural, optical and electrical properties measured before and after thermal annealing, showed that the obtained CdS layers crystallize in the hexagonal structure with a preferential orientation (002) and that the gap value deduced from the transmission measurements is “2.4 eV” with an optical transmission about 80% and resistivity varies between 102 and 103 Ω.cm depending on the bath temperature.

Metal Sulfide Precipitation: Recent Breakthroughs and Future Outlooks

The interest in metal sulfide precipitation has recently increased given its capacity to efficiently recover several metals and metalloids from different aqueous sources, including wastewaters and hydrometallurgical solutions. This article reviews recent studies about metal sulfide precipitation, considering that the most relevant review article on the topic was published in 2010. Thus, our review emphasizes and focuses on the overall process and its main unit operations. This study follows the flow diagram definition, discussing the recent progress in the application of this process on different aqueous matrices to recover/remove diverse metals/metalloids from them, in addition to kinetic reaction and reactor types, different sulfide sources, precipitate behavior, improvements in solid–liquid separation, and future perspectives. The features included in this review are: operational conditions in terms of pH and Eh to perform a selective recovery of different metals contained in an aqueous source, the aggregation/colloidal behavior of precipitates, new materials for controlling sulfide release, and novel solid–liquid separation processes based on membrane filtration. It is therefore relevant that the direct production of nanoparticles (Nps) from this method could potentially become a future research approach with important implications on unit operations, which could possibly expand to several applications.

Metabolism of chiral sulfonate compound 2,3-dihydroxypropane-1-sulfonate (DHPS) by Roseobacter bacteria in marine environment.

The sulfonate compound 2,3-dihydroxypropane-1-sulfonate (DHPS) is one of the most abundant organic sulfur compounds in the biosphere. DHPS derived from dietary intake could be transformed into sulfide by intestinal microbiota and thus impacts human health. However, little is known about its sulfur transformation and subsequent impacts in marine environment. In this study, laboratory-culturing was combined with targeted metabolomic, chemical fluorescence probing, and comparative proteomic methods to examine the bioavailability of chiral DHPS (R and S isomers) for bacteria belonging to the marine Roseobacter clade. The metabolic potential of DHPS in bacteria was further assessed based on genomic analysis. Roseobacter members Ruegeria pomeroyi DSS-3, Dinoroseobacter shibae DFL 12, and Roseobacter denitrificans OCh 114 could utilize chiral DHPS for growth, producing sulfite. They all contained a similar gene cluster for DHPS metabolism but differed in the genes encoding enzymes for desulfonation. There was no significant difference in the growth rate and DHPS consumption rate for R. pomeroyi DSS-3 between R- and S-DHPS cultures, with few proteins expressed differentially were found. Proteomic data suggested that a series of hydrogenases oxidized DHPS, after which desulfonation could proceed via three distinct enzymatic pathways. Strain R. pomeroyi DSS-3 completed the desulfonation via L-cysteate sulfo-lyase, while D. shibae DFL 12 and R. denitrificans OCh 114 primarily utilized sulfolactate sulfo-lyase, and sulfopyruvate decarboxylase followed by sulfoacetaldehyde acetyltransferase, respectively, to complete desulfonation releasing the sulfonate-moiety. The sulfite could be further oxidized or incorporated into sulfate assimilation, indicated by the proteomic data. Furthermore, DHPS metabolic pathways were found primarily in marine bacterial groups, including the majority of sequenced Roseobacter genomes. Our results suggest that chiral DHPS, as a vital reduced sulfur reservoir, could be metabolized by marine bacteria, providing a resource for bacterial growth, rather than acting as a source of toxic sulfide within the marine ecosystem.

Access to Polycyclic Thienoindolines via Formal [2+2+1] Cyclization of Alkynyl Indoles with S8 and K2S.

The syntheses of polycyclic thienoindolines bearing a dihydrothiophene or tetrahydrothiophene subunit have not been reported, despite the fact that such compounds may have interesting medicinal properties. Herein, we report a protocol for accessing polycyclic dihydrothiophenes by means of formal [2+2+1] intramolecular dearomatizing cyclization of alkynyl indoles with K2S and S8 as the sources of sulfide. In addition, tetrahydrothienoindolines were stereoselectively synthesized via a one-pot, two-step protocol involving AgNO3-catalyzed alkenyl dearomatization followed by two nucleophilic addition reactions involving K2S.

Improved effect of manure acidification technology for gas emission mitigation by substituting sulfuric acid with acetic acid

Animal manure is a significant source of ammonia, methane, hydrogen sulfide, and odor emissions. Manure acidification to pH 5.5 using sulfuric acid (H2SO4) is an approved method for reducing ammonia and methane emissions from barns and retaining bioavailable nitrogen in the slurry for subsequent field fertilization. However, the use of H2SO4 may increase the emission of malodorous sulfur compounds and reduces subsequent biogas production. In this study, we investigated if substituting a part of the H2SO4 treatment with acetic acid (CH3COOH) improves manure emissions. In two experiments, cattle manure was incubated for 11 days each and acidified daily with either i) H2SO4 (4M) or CH3COOH (4M), or ii) mixes of both acids (4M H2SO4 + 8M CH3COOH, in volume ratios of 75:25, 50:50, and 25:75) until pH 5.5. The emission of ammonia, methane, hydrogen sulfide, and volatile organic compounds (VOCs) was monitored continuously. At the end of both experiments, cumulative ammonia emission was reduced by 75% by H2SO4 and by 83% by CH3COOH, indicating that CH3COOH was more efficient. Acetic acid almost completely eliminated CH4 emission, while H2SO4 reduced CH4 emission by 89%. Furthermore, CH3COOH acidification resulted in lower odorant emissions compared to H2SO4. Based on the second experiment, we recommend using a high percentage of CH3COOH during the first days of acidification, followed by a mix containing at least 50% CH3COOH, to achieve a high mitigation efficiency with a lower emission of sulfur compounds compared to H2SO4 alone.

Sulfur Biogeochemical Cycle of Marine Sediments

Complex interactions between microbial communities and geochemical processes drive the major element cycles and control the function of marine sediments as a dynamic reservoir of organic matter. Sulfate reduction is globally the dominant pathway of anaerobic mineralisation and is the main source of sulfide. The effective re-oxidation of this sulfide at the direct or indirect expense of oxygen is a prerequisite for aerobic life on our planet. Although largely hidden beneath the oxic sediment surface, the sulfur cycle is therefore critical for Earth’s redox state. This Geochemical Perspectives begins with a brief primer on the sulfur cycle of marine sediments and a description of my own scientific journey through nearly fifty years of studies of sulfur geochemistry and microbiology. Among the main objectives of these studies were to quantify the main processes of the sulfur cycle and to identify the microbial communities behind them. Radiotracers in combination with chemical analyses have thereby been used extensively for laboratory experiments, supported by diverse molecular microbiological methods. The following sections discuss the main processes of sulfate reduction, sulfide oxidation and disproportionation of the inorganic sulfur intermediates, especially of elemental sulfur and thiosulfate. The experimental approaches used enable the analysis of how environmental factors such as substrate concentration or temperature affect process rates and how concurrent processes of sulfate reduction and sulfide oxidation drive a cryptic sulfur cycle. The chemical energy of sulfide is used by chemolithotrophic bacteria, including fascinating communities of big sulfur bacteria and cable bacteria, and supports their dark CO2 fixation, which produces new microbial biomass. During the burial and aging of marine sediments, the predominant mineralisation processes change through a cascade of redox reactions, and the rate of organic matter degradation drops continuously over many orders of magnitude. The main pathways of anaerobic mineralisation and the age control of the organic matter turnover are discussed. In the deep methanic zone, only a few percent of the entire degradation process remains, which provides a small boost of substrate for sulfate reduction through the process of anaerobic methane oxidation. The stable isotopes of sulfur provide an additional tool to understand these diagenetic processes, whereby the combination of microbial isotope fractionation and open system diagenesis generate a differential diffusion flux of the isotopes. In relation to the organic carbon cycle of the seabed and the contribution of methane, the paper discusses the global sulfur budget and the role of sulfate reduction for organic matter mineralisation in different depth regions of the ocean – from coast to deep sea. The published estimates of these parameters are evaluated and compared. Finally, the paper looks at future perspectives with respect to gaps in our current understanding and the need for further studies.