Removal of methanethiol, dimethyl sulfide, dimethyl disulfide, and hydrogen sulfide from contaminated air by Thiobacillus thioparus TK-m

Methanethiol, dimethyl sulfide, dimethyl disulfide, and hydrogen sulfide were efficiently removed from contaminated air by Thiobacillus thioparus TK-m and oxidized to sulfate stoichiometrically. More than 99.99% of dimethyl sulfide was removed when the load was less than 4.0 g of dimethyl sulfide per g (dry cell weight) per day.     

Removal of methanethiol, dimethyl sulfide, dimethyl disulfide, and hydrogen sulfide from contaminated air by Thiobacillus thioparus TK-m.

Methanethiol, dimethyl sulfide, dimethyl disulfide, and hydrogen sulfide were efficiently removed from contaminated air by Thiobacillus thioparus TK-m and oxidized to sulfate stoichiometrically. More than 99.99% of dimethyl sulfide was removed when the load was less than 4.0 g of dimethyl sulfide per g (dry cell weight) per day.     

Removal of dimethyl sulfide,methyl mercaptan,and hydrogen sulfide by immobilized Thiobacillus thioparus TK-m

Cells of Thiobacillus thioparus TK-m were immobilized on cylindrical porous polypropylene pellets (5 mmφ × 5 mm) which were packed in an acrylic cylinder of 50 mm inner diameter up to the height of 800 mm. When a sulfur-containing malodorous gas was charged to this packed tower at the superficial velocity of 0.1 m/s, maximum loading capacity (mmol/l·d) for a malodorous gas to attain the removal rate of 95% or more was: 3.65 for dimethyl sulfide, 8.74 for methyl mercaptan, and 17.36 for hydrogen sulfide. At this time, the inlet concentration (μl/l) of the malodorous compound was: 7.44 for dimethyl sulfide, 17.8 for methyl mercaptan, and 35.4 for hydrogen sulfide. For every compound, higher loading resulted in greater removal quantities. The removal rate of dimethyl sulfide was not overly affected by the presence of a large amount of easily decomposable hydrogen sulfide.     

Sulfide fluxes in a microbial mat from the Ebro Delta, Spain

The sulfur cycle of Ebro Delta microbial mats was studied in order to determine sulfide production and sulfide consumption. Vertical distribution of two major functional groups involved in the sulfur cycle, anoxygenic phototrophic bacteria and dissimilatory sulfate-reducing bacteria (SRB), was also studied. The former reached up to 2.2×10⁸ cfu cm^–3 sediment in the purple layer, and the latter reached about 1.8×10⁵ SRB cm^–3 sediment in the black layer. From the changes in sulfide concentrations under light-dark cycles it can be inferred that the rate of H₂S production was 6.2 μmol H₂S cm^–3 day^–1 at 2.6 mm, and 7.6 μmol H₂S cm^–3 day^–1 at 6 mm. Furthermore, sulfide consumption was also assessed, determining rates of 0.04, 0.13 and 0.005 mmol l^–1 of sulfide oxidized at depths of 2.6, 3 and 6 mm, respectively. Electronic Publication     

Biosynthesis and urinary excretion of methyl sulfonium derivatives of the sulfur mustard analog, 2-chloroethyl ethyl sulfide, and other thioethers

Thioether methyltransferase was previously shown to catalyze the S-adenosylmethionine-dependent methylation of dimethyl selenide, dimethyl telluride, and various thioethers to produce the corresponding methyl onium ions. In this paper we show that the following thioethers are also substrates for this enzyme in vitro: 2-hydroxyethyl ethyl sulfide, 2-chloroethyl ethyl sulfide, thiodiglycol, t-butyl sulfide, and isopropyl sulfide. To demonstrate thioether methylation in vivo, mice were injected with [methyl-3H]methionine plus different thioethers, and extracts of lungs, livers, kidneys, and urine were analyzed by high-performance liquid chromatography for the presence of [3H]methyl sulfonium ions. The following thioethers were tested, and all were found to be methylated in vivo: dimethyl sulfide, diethyl sulfide, methyl n-propyl sulfide, tetrahydrothiophene, 2-(methylthio)ethylamine, 2-hydroxyethyl ethyl sulfide, and 2-chloroethyl ethyl sulfide. This supports our hypothesis that the physiological role of thioether methyltransferase is to methylate seleno-, telluro-, and thioethers to more water-soluble onium ions suitable for urinary excretion. Conversion of the mustard gas analog, 2-chloroethyl ethyl sulfide, to the methyl sulfonium derivative represents a newly discovered mechanism for biochemical detoxification of sulfur mustards, as this conversion blocks formation of the reactive episulfonium ion that is the ultimate alkylating agent for this class of compounds.     

Motility of Marichromatium gracile in response to light, oxygen, and sulfide.

The motility of the purple sulfur bacterium Marichromatium gracile was investigated under different light regimes in a gradient capillary setup with opposing oxygen and sulfide gradients. The gradients were quantified with microsensors, while the behavior of swimming cells was studied by video microscopy in combination with a computerized cell tracking system. M. gracile exhibited photokinesis, photophobic responses, and phobic responses toward oxygen and sulfide. The observed migration patterns could be explained solely by the various phobic responses. In the dark, M. gracile formed an approximately 500-microm-thick band at the oxic-anoxic interface, with a sharp border toward the oxic zone always positioned at approximately 10 microM O(2). Flux calculations yielded a molar conversion ratio S(tot)/O(2) of 2.03:1 (S(tot) = [H(2)S] + [HS(-)] + [S(2-)]) for the sulfide oxidation within the band, indicating that in darkness the bacteria oxidized sulfide incompletely to sulfur stored in intracellular sulfur globules. In the light, M. gracile spread into the anoxic zone while still avoiding regions with >10 microM O(2). The cells also preferred low sulfide concentrations if the oxygen was replaced by nitrogen. A light-dark transition experiment demonstrated a dynamic interaction between the chemical gradients and the cell's metabolism. In darkness and anoxia, M. gracile lost its motility after ca. 1 h. In contrast, at oxygen concentrations of >100 microM with no sulfide present the cells remained viable and motile for ca. 3 days both in light and darkness. Oxygen was respired also in the light, but respiration rates were lower than in the dark. Observed aggregation patterns are interpreted as effective protection strategies against high oxygen concentrations and might represent first stages of biofilm formation.     

Sulfide-hemoglobin interactions in the sulfide-tolerant salt marsh resident,the California killifish Fundulus parvipinnis

Summary Sulfide can potentially damage hemoglobin or be detoxified by hemoglobin. In the sulfide-tolerant California killifish neither seems to be the case at environmentally realistic (micromolar) and physiologically relevant (millimolar) sulfide concentrations. An 8-h exposure of killifish to 5 and 8 mmol sulfide · 1^-1 results in 50–100% mortality, but not due to sulfhemoglobin (where sulfide covalently binds to the porphyrin) nor ferric hemoglobin (Hb⁺), both dysfunctional hemoglobin derivatives. Killifish hemoglobin converts to sulfhemoglobin in vitro only in the presence of 1–5 mmol sulfide · 1^-1. The amount of sulfhemoglobin formed increases with time and heme concentration but decreases with pH. Hb⁺ binds sulfide as ferric hemoglobin sulfide (Hb⁺S, an unstable complex where sulfide ligates to the iron), and also as sulfhemoglobin. Killifish blood does not catalyze the oxidation of 10–500 mol sulfide · 1^-1 to any appreciable extent. Radiolabeled sulfide incubated with oxyhemoglobin or whole blood disappears at rates greater than in buffers, but only minimal amounts of thiosulfate and no sulfate nor sulfite are formed (elemental sulfur and bound sulfide not quantified). Sulfide disappearance rates increase linearly with initial sulfide concentration. Hb⁺ does catalyze the oxidation of sulfide to thiosulfate in vitro. Similar experiments on another sulfide-tolerant species, the long-jawed mudsucker Gillichthys mirabilis, produced similar results.Abbreviations ANOVA analysis of variance - BV benzyl viologen - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - HPLC high-pressure liquid chromatography - RBC red blood cells - SHb sulfhemoglobin     

Taxonomic distribution,structure/function relationship and metabolic context of the two families of sulfide dehydrogenases: SQR and FCSD

Hydrogen sulfide (H₂S) is a versatile molecule with different functions in living organisms: it can work as a metabolite of sulfur and energetic metabolism or as a signaling molecule in higher Eukaryotes. H₂S is also highly toxic since it is able to inhibit heme cooper oxygen reductases, preventing oxidative phosphorylation. Due to the fact that it can both inhibit and feed the respiratory chain, the immediate role of H₂S on energy metabolism crucially relies on its bioavailability, meaning that studying the central players involved in the H₂S homeostasis is key for understanding sulfide metabolism.Two different enzymes with sulfide oxidation activity (sulfide dehydrogenases) are known: flavocytochrome c sulfide dehydrogenase (FCSD), a sulfide:cytochrome c oxidoreductase; and sulfide:quinone oxidoreductase (SQR).In this work we performed a thorough bioinformatic study of SQRs and FCSDs and integrated all published data. We systematized several properties of these proteins: (i) nature of flavin binding, (ii) capping loops and (iii) presence of key amino acid residues. We also propose an update to the SQR classification system and discuss the role of these proteins in sulfur metabolism.     

Methane, Carbon Dioxide, and Hydrogen Sulfide Production from the Terminal Methiol Group of Methionine by Anaerobic Lake Sediments

A significant portion of the sulfide in lake sediments may be derived from sulfur-containing amino acids. Methionine degradation in Lake Mendota (Wisconsin) sediments was studied with gas chromatographic and radiotracer techniques. Temperature optimum and inhibitor studies showed that this process was biological. Methane thiol and dimethyl sulfide were produced in sediments when 1-μmol/ml unlabeled methionine was added. When chloroform (an inhibitor of one-carbon metabolism) was added to the sediments, methane thiol, carbon disulfide, and n-propane thiol were produced, even when no methionine was added. When ³⁵S-labeled methionine was added to the sediments in tracer quantities (1.75 nmol/ml), labeled hydrogen sulfide was produced, and a roughly equal amount of label was incorporated into insoluble material. Methane and carbon dioxide were produced from [methyl-¹⁴C]methionine. Evidence is given favoring methane thiol as an intermediate in the formation of methane, carbon dioxide, and hydrogen sulfide from the terminal methiol group of methionine. Methionine may be an important source of sulfide in lake sediments.     

Complete degradation of Yperite, a chemical warfare agent, by basidiomycetes

The complete degradation of Yperite (bis(2-chloroethyl) sulfide), a chemical warfare agent, was achieved by two basidiomycetous cultures. Two distinct metabolic pathways were detected in each fungus during degradation of Yperite. The major path involved a non-enzymatic hydrolysis to generate thiodiglycol. In the minor path, the sulfide bond was cleaved prior to the hydrolytic dechlorination reaction, yielding chloroethanol and chloromercaptoethane, both of which were then metabolized completely.     

Velocity changes, long runs, and reversals in the Chromatium minus swimming response.

The velocity, run time, path curvature, and reorientation angle of Chromatium minus were measured as a function of light intensity, temperature, viscosity, osmotic pressure, and hydrogen sulfide concentration. C. minus changed both velocity and run time. Velocity decreased with increasing light intensity in sulfide-depleted cultures and increased in sulfide-replete cultures. The addition of sulfide to cultures grown at low light intensity (10 microeinsteins m-2 s-1) caused mean run times to increase from 10.5 to 20.6 s. The addition of sulfide to cultures grown at high light intensity (100 microeinsteins m-2 s-1) caused mean run times to decrease from 15.3 to 7.7 s. These changes were maintained for up to an hour and indicate that at least some members of the family Chromatiaceae simultaneously modulate velocity and turning frequency for extended periods as part of normal taxis.     

Linking geology,fluid chemistry,and microbial activity of basalt‐ and ultramafic‐hosted deep‐sea hydrothermal vent environments

Hydrothermal fluids passing through basaltic rocks along mid‐ocean ridges are known to be enriched in sulfide, while those circulating through ultramafic mantle rocks are typically elevated in hydrogen. Therefore, it has been estimated that the maximum energy in basalt‐hosted systems is available through sulfide oxidation and in ultramafic‐hosted systems through hydrogen oxidation. Furthermore, thermodynamic models suggest that the greatest biomass potential arises from sulfide oxidation in basalt‐hosted and from hydrogen oxidation in ultramafic‐hosted systems. We tested these predictions by measuring biological sulfide and hydrogen removal and subsequent autotrophic CO₂ fixation in chemically distinct hydrothermal fluids from basalt‐hosted and ultramafic‐hosted vents. We found a large potential of microbial hydrogen oxidation in naturally hydrogen‐rich (ultramafic‐hosted) but also in naturally hydrogen‐poor (basalt‐hosted) hydrothermal fluids. Moreover, hydrogen oxidation–based primary production proved to be highly attractive under our incubation conditions regardless whether hydrothermal fluids from ultramafic‐hosted or basalt‐hosted sites were used. Site‐specific hydrogen and sulfide availability alone did not appear to determine whether hydrogen or sulfide oxidation provides the energy for primary production by the free‐living microbes in the tested hydrothermal fluids. This suggests that more complex features (e.g., a combination of oxygen, temperature, biological interactions) may play a role for determining which energy source is preferably used in chemically distinct hydrothermal vent biotopes.     

Enzymatic methylation of sulfide, selenide, and organic thiols by Tetrahymena thermophila

Cell extracts from the ciliate Tetrahymena thermophila catalyzed the S-adenosylmethionine-dependent methylation of sulfide. The product of the reaction, methanethiol, was detected by a radiometric assay and by a gas-chromatographic assay coupled to a sulfur-selective chemiluminescence detector. Extracts also catalyzed the methylation of selenide, and the product was shown by gas chromatography-mass spectrometry to be methaneselenol. The sulfide and selenide methyltransferase activities copurified with the aromatic thiol methyltransferase previously characterized from this organism (A.-M. Drotar and R. Fall, Pestic. Biochem. Physiol. 25:396-406, 1986), but heat inactivation experiments suggested the involvement of distinct sulfide and selenide methyltransferases. Short-term toxicity tests were carried out for sulfide, selenide, and their methylated derivatives; the monomethylated forms were somewhat more toxic than the nonmethylated or dimethylated compounds. Cell suspensions of T. thermophila exposed to sulfide, methanethiol, or their selenium analogs emitted methylated derivatives into the headspace. These results suggest that this freshwater protozoan is capable of the stepwise methylation of sulfide and selenide, leading to the release of volatile methylated sulfur or selenium gases.     

Rice: sulfide-induced barriers to root radial oxygen loss, Fe2+ and water uptake, and lateral root emergence

BACKGROUND AND AIMS: Akagare and Akiochi are diseases of rice associated with sulfide toxicity. This study investigates the possibility that rice reacts to sulfide by producing impermeable barriers in roots. METHODS: Root systems of rice, Oryza sativa cv. Norin 36, were subjected to short-term exposure to 0.174 mm sulfide (5.6 ppm) in stagnant solution. Root growth was monitored; root permeability was investigated in terms of polarographic determinations of oxygen efflux from fine laterals and the apices of adventitious roots, water uptake, anatomy and permeability to Fe2+ using potassium ferricyanide. KEY RESULTS: Both types of root responded rapidly to the sulfide with immediate cessation of growth, decreased radial oxygen loss (ROL) to the rhizospheres and reduced water uptake. Profiles of ROL measured from apex to basal regions of adventitious roots indicated that more intense barriers to ROL than normal were formed around the apices. Absorption of Fe2+ appeared to be impeded in sulfide-treated roots. In adventitious roots, deposition of lipid material (suberisation) and thickenings of walls within the superficial cell layers were obvious within a week after lifting the treatment and could prevent the emergence of laterals and commonly result in their upward longitudinal growth within the cortex. Death of laterals sometimes occurred prior to emergence; emergent laterals eventually died. In adventitious roots, blockages formed within the vascular and aeration systems in response to the sulfide. CONCLUSIONS: In both adventitious and lateral roots, sulfide-induced cell wall suberization and thickening of the superficial layers were correlated with reduced permeability to O2, water and Fe2+. This study sheds light on some of the symptoms of diseases such as Akiochi. The results correlate with the authors' previous findings on the effects on roots of sulfide and lower organic acids in Phragmites and of acetic acid in rice.     

Measurement of H2S in Crude Oil and Crude Oil Headspace Using Multidimensional Gas Chromatography,Deans Switching and Sulfur-selective Detection

A method for the analysis of dissolved hydrogen sulfide in crude oil samples is demonstrated using gas chromatography. In order to effectively eliminate interferences, a two dimensional column configuration is used, with a Deans switch employed to transfer hydrogen sulfide from the first to the second column (heart-cutting). Liquid crude samples are first separated on a dimethylpolysiloxane column, and light gases are heart-cut and further separated on a bonded porous layer open tubular (PLOT) column that is able to separate hydrogen sulfide from other light sulfur species. Hydrogen sulfide is then detected with a sulfur chemiluminescence detector, adding an additional layer of selectivity. Following separation and detection of hydrogen sulfide, the system is backflushed to remove the high-boiling hydrocarbons present in the crude samples and to preserve chromatographic integrity. Dissolved hydrogen sulfide has been quantified in liquid samples from 1.1 to 500 ppm, demonstrating wide applicability to a range of samples. The method has also been successfully applied for the analysis of gas samples from crude oil headspace and process gas bags, with measurement from 0.7 to 9,700 ppm hydrogen sulfide.     

Enzymatic methylation of sulfide, selenide, and organic thiols by Tetrahymena thermophila.

Cell extracts from the ciliate Tetrahymena thermophila catalyzed the S-adenosylmethionine-dependent methylation of sulfide. The product of the reaction, methanethiol, was detected by a radiometric assay and by a gas-chromatographic assay coupled to a sulfur-selective chemiluminescence detector. Extracts also catalyzed the methylation of selenide, and the product was shown by gas chromatography-mass spectrometry to be methaneselenol. The sulfide and selenide methyltransferase activities copurified with the aromatic thiol methyltransferase previously characterized from this organism (A.-M. Drotar and R. Fall, Pestic. Biochem. Physiol. 25:396-406, 1986), but heat inactivation experiments suggested the involvement of distinct sulfide and selenide methyltransferases. Short-term toxicity tests were carried out for sulfide, selenide, and their methylated derivatives; the monomethylated forms were somewhat more toxic than the nonmethylated or dimethylated compounds. Cell suspensions of T. thermophila exposed to sulfide, methanethiol, or their selenium analogs emitted methylated derivatives into the headspace. These results suggest that this freshwater protozoan is capable of the stepwise methylation of sulfide and selenide, leading to the release of volatile methylated sulfur or selenium gases.     

The Geological Roles Played by Microfungi in Interaction with Sulfide Minerals from Libiola Mine,Liguria, Italy

The potential role played by fungi in the weathering of sulfide abandoned mines and waste rock dumps is scarcely investigated, yet. In particular microfungi may produce biofilms that work as sites of metals and minerals precipitation. This study aimed to investigate interactions, bioalteration, and biocorrosion between three microfungi (Trichoderma harzianum group, Penicillium glandicola, P. brevicompactum) isolated from the Libiola sulfide mine (Liguria, Italy) and pyrite-rich mineralizations occurring within the waste rock dumps. After six weeks of incubation, Environmental Scanning Electron Microscope (ESEM) analyses showed how single pyrite crystals were completely corroded and altered by all the selected species. These results represent the first step to establish that fungi play a central role in the biogeochemical cycles of extreme and contaminated sites such as sulfide mines, and that they actively contribute to the evolution of the degraded ecosystem to more harmonized scenery.     

Dissimilatory arsenate reduction with sulfide as electron donor: experiments with mono lake water and Isolation of strain MLMS-1, a chemoautotrophic arsenate respirer

Anoxic bottom water from Mono Lake, California, can biologically reduce added arsenate without any addition of electron donors. Of the possible in situ inorganic electron donors present, only sulfide was sufficiently abundant to drive this reaction. We tested the ability of sulfide to serve as an electron donor for arsenate reduction in experiments with lake water. Reduction of arsenate to arsenite occurred simultaneously with the removal of sulfide. No loss of sulfide occurred in controls without arsenate or in sterilized samples containing both arsenate and sulfide. The rate of arsenate reduction in lake water was dependent on the amount of available arsenate. We enriched for a bacterium that could achieve growth with sulfide and arsenate in a defined, mineral medium and purified it by serial dilution. The isolate, strain MLMS-1, is a gram-negative, motile curved rod that grows by oxidizing sulfide to sulfate while reducing arsenate to arsenite. Chemoautotrophy was confirmed by the incorporation of H(14)CO(3)(-) into dark-incubated cells, but preliminary gene probing tests with primers for ribulose-1,5-biphosphate carboxylase/oxygenase did not yield PCR-amplified products. Alignment of 16S rRNA sequences indicated that strain MLMS-1 was in the delta-Proteobacteria, located near sulfate reducers like Desulfobulbus sp. (88 to 90% similarity) but more closely related (97%) to unidentified sequences amplified previously from Mono Lake. However, strain MLMS-1 does not grow with sulfate as its electron acceptor.     

Nitrate-reducing, sulfide-oxidizing bacteria as microbial oxidants for rapid biological sulfide removal

The emission of hydrogen sulfide into the atmosphere of sewer systems induces the biological production of sulfuric acid, causing severe concrete corrosion. As a possible preventive solution, a microbial consortium of nitrate-reducing, sulfide-oxidizing bacteria (NR-SOB) was enriched in a continuously stirred tank reactor in order to develop a biological technique for the removal of dissolved sulfide. The consortium, dominated by Arcobacter sp., was capable of removing 99% of sulfide. Stable isotope fractioning of the sulfide indicated that the oxidation was a biological process. The capacity of the NR-SOB consortium for rapid removal of sulfide was demonstrated by using it as an inoculum in synthetic and real sewage. Removal rates up to 52 mg sulfide-S g VSS⁻¹ h⁻¹ were achieved, to our knowledge the highest removal rate reported so far for freshwater species in the absence of molecular oxygen. Further long-term incubation experiments revealed the capacity of the bacteria to oxidize sulfide without the presence of nitrate, suggesting that an oxidized redox reserve is present in the culture.     

Measurement and biological significance of the volatile sulfur compounds hydrogen sulfide,methanethiol and dimethyl sulfide in various biological matrices

This review deals with the measurement of the volatile sulfur compounds hydrogen sulfide, methanethiol and dimethyl sulfide in various biological matrices of rats and humans (blood, serum, tissues, urine, breath, feces and flatus). Hydrogen sulfide and methanethiol both contain the active thiol (–SH) group and appear in the free gaseous form, in the acid-labile form and in the dithiothreitol-labile form. Dimethyl sulfide is a neutral molecule and exists only in the free form. The foul odor of these sulfur volatiles is a striking characteristic and plays a major role in bad breath, feces and flatus. Because sulfur is a biologically active element, the biological significance of the sulfur volatiles are also highlighted. Despite its highly toxic properties, hydrogen sulfide has been lately recommended to become the third gasotransmitter, next to nitric oxide and carbon monoxide, based on high concentration found in healthy tissues, such as blood and brain. However, there is much doubt about the reliability of the assay methods used. Many artifacts in the sulfide assays exist. The methods to detect the various forms of hydrogen sulfide are critically reviewed and compared with findings of our group. Recent findings that free gaseous hydrogen sulfide is absent in whole blood urged the need to revisit its role as a blood-borne signaling molecule.