Reduced Sulfur Compounds Research Articles

Spatial distributions of sulphur species and sulphate-reducing bacteria provide insights into sulphur redox cycling and biodegradation hot-spots in a hydrocarbon-contaminated aquifer

Dissimilatory sulphate reduction (DSR) has been proven to be one of the most relevant redox reactions in the biodegradation of contaminants in groundwater. However, the possible role of sulphur species of intermediate oxidation state, as well as the role of potential re-oxidative sulphur cycling in biodegradation particularly at the groundwater table are still poorly understood. Here we used a combination of stable isotope measurements of SO42−, H2S, and S0 as well as geochemical profiling of sulphur intermediates with special emphasis on SO32−, S2O32−, and S0 to unravel possible sulphur cycling in the biodegradation of aromatics in a hydrocarbon-contaminated porous aquifer. By linking these results to the quantification of total bacterial rRNA genes and respiratory genes of sulphate reducers, as well as pyrotag sequencing of bacterial communities over depth, light is shed on possible key-organisms involved.Our results substantiate the role of DSR in biodegradation of hydrocarbons (mainly toluene) in the highly active plume fringes above and beneath the plume core. In both zones the concentration of sulphur intermediates (S0, SO32− and S2O32−) was almost twice that of other sampling-depths, indicating intense sulphur redox cycling. The dual isotopic fingerprint of oxygen and sulphur in dissolved sulphate suggested a re-oxidation of reduced sulphur compounds to sulphate especially at the upper fringe zone. An isotopic shift in δ34S of S0 of nearly +4‰ compared to the δ34S values of H2S from the same depth linked to a high abundance (∼10%) of sequence reads related to Sulphuricurvum spp. (Epsilonproteobacteria) in the same depth were indicative of intensive oxidation of S0 to sulphate in this zone. At the lower plume fringe S0 constituted the main inorganic sulphur species, possibly formed by abiotic re-oxidation of H2S with Fe(III)oxides subsequent to sulphate reduction. These results provide first insights into intense sulphur redox cycling in a hydrocarbon contaminant plume, which widens the perspective of redox processes and microbial interactions ongoing in contaminated aquifers.

Emissions from oil sands tailings ponds: Review of tailings pond parameters and emission estimates

The storage of large volumes of tailings has become an issue for Canada׳s oil sands industry. The use of diluent, along with incomplete bitumen and solvent recovery from the tailings stream, leads to the accumulation of organic compounds within tailings ponds. Volatile organic compounds, reduced sulfur compounds, carbon dioxide, and methane are emitted from tailings outfalls, oily films, bitumen slicks, and mature fine tailings. These emissions are linked to the bitumen extraction and tailings treatment processes, tailings properties (composition, age, residence time), and environmental factors (wind, temperature, rain, and ice cover). Due to limited research in this area, it is difficult to evaluate relationships between emission sources and compounds emitted. To estimate emissions, emission factors based on snapshot measurements, and varying models and assumptions are commonly used. This review presents current knowledge on factors and parameters influencing emission estimates, and challenges pertaining to the development of current emissions factors. Standard emission measurement and calculation methods, vigilant sampling, and increased research are needed to develop a more accurate and representative understanding of emissions from oil sands tailings ponds. • Oil sands tailings are heterogeneous sources of VOC, CO 2 , CH 4 , and RSC emissions. • Knowledge gap and research needs to improve emissions measurement were identified. • Understanding the impact of ice melt and microbial activity on emissions is needed. • Methods that capture the spatial and temporal variation of emissions are needed.

Thioautotrophic bacterial endosymbionts are degraded by enzymatic digestion during starvation: Case study of two lucinids Codakia orbicularis and C. orbiculata.

The Caribbean bivalves Codakia orbicularis (Linné, 1758) and C. orbiculata (Montagu, 1808) live in seagrass beds of Thalassia testudinum and harbor intracellular sulfur-oxidizing gamma-proteobacteria. These bacterial symbionts fix CO2 via the Calvin Benson cycle and provide organic compounds to the bivalve. During experimentally induced starvation, no reduced sulfur compounds and no organic particle food are available; the symbionts could be considered as the sole nutrient source of the host bivalve. A previous study has shown that the intracellular bacterial population decreased considerably during starvation and that bacterial endosymbionts were not released by the bivalves. In this study, the activity of two lysosomal marker enzymes (acid phosphatase and arylsulfatase) was detected using cytochemical experiments coupled with energy-dispersive X-ray transmission electron microscopy during sulfide and organic particle starvation. The degradation of bacterial endosymbionts began after 2 weeks of starvation in C. orbiculata and after 3 weeks in C. orbicularis. Degradation processes seem to be continuous over several months and could be responsible for the disappearance of the bacterial endosymbionts within the gills during starvation. These data suggest that the host use symbionts as a nutrient source to survive a hunger crisis. The carbon transfer from the symbionts to the host could be flexible and could consist in transfer of organic matter, "milking," under normal feeding conditions and digestion of the symbionts under starved conditions.

Beneficial co-treatment of simple wet flue gas desulphurization wastes with freshwater sewage through development of mixed denitrification–SANI process

Sulphate reduction, autotrophic denitrification and nitrification integrated (SANI) process was developed for saline sewage treatment with 90% sludge minimization. This study is further to develop a new SANI, i.e., mixed denitrification (MD)–SANI for beneficial co-treatment of flue gas desulphurization (FGD) wastes with typical sewage through simple wet FGD and energy-efficient sewage treatment. In order to confirm the potential benefits of MD–SANI process, a lab-scale system was operated with mixtures of sulphite, sulphate and synthetic freshwater sewage. Biological co-reduction of sulphite and sulphate in the anaerobic reactor resulted in sufficient sulphide, thiosulphate and residual volatile fatty acids (VFAs) for efficient MD including autotrophic denitrification (AD) on sulphide, AD on thiosulphate, and heterotrophic denitrification (HD) on VFAs in the subsequent anoxic upflow sludge bed (AnUSB). The MD–SANI process increased denitrification rate by seven-time compared with sulphide-based AD in the original SANI. The AD and HD contributed to 72% and 28% of the MD capacity respectively without accumulation of elemental sulphur or reduced sulphur compounds in the final effluent. The MD–SANI process produced sufficient alkalinity not only for its own consumption in aerobic and anoxic reactors but also for potential reuse in SO2 absorption in simple wet FGD practice. The overall sludge yield of MD–SANI process was determined to be 0.03 kgVSS/kgCOD, inheriting the main feature of SANI process in sludge minimization. All these main findings in this study justify simple wet FGD and support co-treatment of its wastes with freshwater sewage to provide potential benefits for both air pollution control and water industries.

Variation in sulfur and selenium accumulation is controlled by naturally occurring isoforms of the key sulfur assimilation enzyme ADENOSINE 5'-PHOSPHOSULFATE REDUCTASE2 across the Arabidopsis species range.

Natural variation allows the investigation of both the fundamental functions of genes and their role in local adaptation. As one of the essential macronutrients, sulfur is vital for plant growth and development and also for crop yield and quality. Selenium and sulfur are assimilated by the same process, and although plants do not require selenium, plant-based selenium is an important source of this essential element for animals. Here, we report the use of linkage mapping in synthetic F2 populations and complementation to investigate the genetic architecture of variation in total leaf sulfur and selenium concentrations in a diverse set of Arabidopsis (Arabidopsis thaliana) accessions. We identify in accessions collected from Sweden and the Czech Republic two variants of the enzyme ADENOSINE 5'-PHOSPHOSULFATE REDUCTASE2 (APR2) with strongly diminished catalytic capacity. APR2 is a key enzyme in both sulfate and selenate reduction, and its reduced activity in the loss-of-function allele apr2-1 and the two Arabidopsis accessions Hodonín and Shahdara leads to a lowering of sulfur flux from sulfate into the reduced sulfur compounds, cysteine and glutathione, and into proteins, concomitant with an increase in the accumulation of sulfate in leaves. We conclude from our observation, and the previously identified weak allele of APR2 from the Shahdara accession collected in Tadjikistan, that the catalytic capacity of APR2 varies by 4 orders of magnitude across the Arabidopsis species range, driving significant differences in sulfur and selenium metabolism. The selective benefit, if any, of this large variation remains to be explored.

Kinetic leaching of high sulphur mine rejects amended with biochar: Buffering implication

In the present investigation, the effect of biochar incorporation into high sulphur mine rejects on buffering of the acid production was assessed. For this, kinetic experiments on pure mine rejects (LMR) and biochar amended mine rejects (LMRBC) were performed for 720h. Leachate samples were collected at 0, 20, 40, 60, 168, 336, 504 and 720h and characterized. Results revealed that incorporation of biochar inhibited the acid production rate (from 10.4kg/Mt/h to 3.81kg/Mt/h) and enhanced the alkali consumption (from 9.7kg/Mt/h to 13.9kg/Mt/h). Biochar was capable to neutralize all the acid produced. As a neutralizing agent, Mg2+ dominated over Ca2+. The efficiency of biochar to reduce the rate of acid production may be due to either the reduction in Fe3+ concentration or production of reduced sulphur compounds in reducing conditions of biochar. This is also supported by molar sulphur to iron ratio of leachate water. Principal component analysis applied on the data revealed that biochar altered the salt and carbon dissolution processes of mine rejects. It inhibits the acid production and accelerates the alkali releasing.

The role of hydrogen for Sulfurimonas denitrificans' metabolism.

Sulfurimonas denitrificans was originally isolated from coastal marine sediments. It can grow with thiosulfate and nitrate or sulfide and oxygen. Recently sequencing of its genome revealed that it encodes periplasmic and cytoplasmic [NiFe]-hydrogenases but the role of hydrogen for its metabolism has remained unknown. We show the first experimental evidence that S. denitrificans can indeed express a functional hydrogen uptake active hydrogenase and can grow on hydrogen. In fact, under the provided conditions it grew faster and denser on hydrogen than on thiosulfate alone and even grew with hydrogen in the absence of reduced sulfur compounds. In our experiments, at the time points tested, the hydrogen uptake activity appeared to be related to the periplasmic hydrogenase and not to the cytoplasmic hydrogenase. Our data suggest that under the provided conditions S. denitrificans can grow more efficiently with hydrogen than with thiosulfate.

CysK2 from Mycobacterium tuberculosis is an O-phospho-L-serine-dependent S-sulfocysteine synthase.

Mycobacterium tuberculosis is dependent on cysteine biosynthesis, and reduced sulfur compounds such as mycothiol synthesized from cysteine serve in first-line defense mechanisms against oxidative stress imposed by macrophages. Two biosynthetic routes to l-cysteine, each with its own specific cysteine synthase (CysK1 and CysM), have been described in M. tuberculosis, but the function of a third putative sulfhydrylase in this pathogen, CysK2, has remained elusive. We present biochemical and biophysical evidence that CysK2 is an S-sulfocysteine synthase, utilizing O-phosphoserine (OPS) and thiosulfate as substrates. The enzyme uses a mechanism via a central aminoacrylate intermediate that is similar to that of other members of this pyridoxal phosphate-dependent enzyme family. The apparent second-order rate of the first half-reaction with OPS was determined as kmax/Ks = (3.97 × 10(3)) ± 619 M(-1) s(-1), which compares well to the OPS-specific mycobacterial cysteine synthase CysM with a kmax/Ks of (1.34 × 10(3)) ± 48.2. Notably, CysK2 does not utilize thiocarboxylated CysO as a sulfur donor but accepts thiosulfate and sulfide as donor substrates. The specificity constant kcat/Km for thiosulfate is 40-fold higher than for sulfide, suggesting an annotation as S-sulfocysteine synthase. Mycobacterial CysK2 thus provides a third metabolic route to cysteine, either directly using sulfide as donor or indirectly via S-sulfocysteine. Hypothetically, S-sulfocysteine could also act as a signaling molecule triggering additional responses in redox defense in the pathogen upon exposure to reactive oxygen species during dormancy.

Microbial controls on DMSP degradation and DMS formation in the Sargasso Sea

Bacterial degradation of dimethylsulfoniopropionate (DMSP) represents one of the main sources of the climatically–active trace gas dimethylsulfide (DMS) in the upper ocean. Short-term enrichment studies to stimulate specific pathways of DMSP degradation in oligotrophic waters from the Sargasso Sea were used to explore regulatory connections between the different bacterial DMSP degradation steps and determine potential biological controls on DMS formation in the open ocean. Experiments were conducted with surface water at the BATS station in the western North Atlantic Ocean. We added selected organic substrates (25 nmol L−1 final concentration) to induce different steps of DMSP degradation in the microbial community, and then measured DMSP dynamics (assimilation and turnover rates), DMS yields (using 35sulfur-DMSP tracer), and bacterial production rates. In most treatments, the main fate of consumed S-DMSP was excretion as a non-volatile S product. 35S-DMSP tracer turnover rates (accumulation + assimilation + excretion of transformed products as DMS or others) increased upon addition of DMSP and glucose, but not acrylate, methymercaptopropionate (MMPA), methanethiol, DMS or glycine betaine. DMS yields from 35S-DMSP never exceeded 16 % except in a short term DMSP enrichment, for which the yield reached 45 % (±17 %). Results show that availability of non-sulfur containing labile C sources (glucose, acrylate) decreased bacterial DMS production while stimulating bacterial heterotrophic production, and suggest an influence of bacterial sulfur demand in controlling DMS-yielding pathways. However, regulatory effects on 35S-DMSP fate were not consistent across all reduced sulfur compounds (i.e., methanethiol or MMPA), and may reflect alternate roles of DMSP as a bacterial energy source and osmolyte.

Metabolomic profiling of the purple sulfur bacterium Allochromatium vinosum during growth on different reduced sulfur compounds and malate.

Environmental fluctuations require rapid adjustment of the physiology of bacteria. Anoxygenic phototrophic purple sulfur bacteria, like Allochromatium vinosum, thrive in environments that are characterized by steep gradients of important nutrients for these organisms, i.e., reduced sulfur compounds, light, oxygen and carbon sources. Changing conditions necessitate changes on every level of the underlying cellular and molecular network. Thus far, two global analyses of A. vinosum responses to changes of nutritional conditions have been performed and these focused on gene expression and protein levels. Here, we provide a study on metabolite composition and relate it with transcriptional and proteomic profiling data to provide a more comprehensive insight on the systems level adjustment to available nutrients. We identified 131 individual metabolites and compared availability and concentration under four different growth conditions (sulfide, thiosulfate, elemental sulfur, and malate) and on sulfide for a ΔdsrJ mutant strain. During growth on malate, cysteine was identified to be the least abundant amino acid. Concentrations of the metabolite classes “amino acids” and “organic acids” (i.e., pyruvate and its derivatives) were higher on malate than on reduced sulfur compounds by at least 20 and 50 %, respectively. Similar observations were made for metabolites assigned to anabolism of glucose. Growth on sulfur compounds led to enhanced concentrations of sulfur containing metabolites, while other cell constituents remained unaffected or decreased. Incapability of sulfur globule oxidation of the mutant strain was reflected by a low energy level of the cell and consequently reduced levels of amino acids (40 %) and sugars (65 %).Electronic supplementary materialThe online version of this article (doi:10.1007/s11306-014-0649-7) contains supplementary material, which is available to authorized users.

Bacterial pathogen indicators regrowth and reduced sulphur compounds’ emissions during storage of electro-dewatered biosolids

Electro-dewatering (ED) increases biosolids dryness from 10–15 to 30–50%, which helps wastewater treatment facilities control disposal costs. Previous work showed that high temperatures due to Joule heating during ED inactivate total coliforms to meet USEPA Class A biosolids requirements. This allows biosolids land application if the requirements are still met after the storage period between production and application. In this study, we examined bacterial regrowth and odour emissions during the storage of ED biosolids. No regrowth of total coliforms was observed in ED biosolids over 7d under aerobic or anaerobic incubations. To mimic on-site contamination during storage or transport, ED samples were seeded with untreated sludge. Total coliform counts decreased to detection limits after 4d in inoculated samples. Olfactometric analysis of ED biosolids odours showed that odour concentrations were lower compared to the untreated and heat-treated control biosolids. Furthermore, under anaerobic conditions, odorous reduced sulphur compounds (methanethiol, dimethyl sulphide and dimethyl disulphide) were produced by untreated and heat-treated biosolids, but were not detected in the headspaces above ED samples. The data demonstrate that ED provides advantages not only as a dewatering technique, but also for producing biosolids with lower microbial counts and odour levels.

Characterizing reduced sulfur compounds emissions from a swine concentrated animal feeding operation

Reduced sulfur compounds (RSCs) emissions from concentrated animal feeding operations (CAFOs) have become a potential environmental and human health concern, as a result of changes in livestock production methods. RSC emissions were determined from a swine CAFO in North Carolina. RSC measurements were made over a period of ≈1 week from both the barn and lagoon during each of the four seasonal periods from June 2007 to April 2008. During sampling, meteorological and other environmental parameters were measured continuously. Seasonal hydrogen sulfide (H2S) barn concentrations ranged from 72 to 631 ppb. Seasonal dimethyl sulfide (DMS; CH3SCH3) and dimethyl disulfide (DMDS; CH3S2CH3) concentrations were 2–3 orders of magnitude lower, ranging from 0.18 to 0.89 ppb and 0.47 to 1.02 ppb, respectively. The overall average barn emission rate was 3.3 g day−1 AU−1 (AU (animal unit) = 500 kg of live animal weight) for H2S, which was approximately two orders of magnitude higher than the DMS and DMDS overall average emissions rates, determined as 0.017 g day−1 AU−1 and 0.036 g day−1 AU−1, respectively. The overall average lagoon flux was 1.33 μg m−2 min−1 for H2S, which was approximately an order of magnitude higher than the overall average DMS (0.12 μg m−2 min−1) and DMDS (0.09 μg m−2 min−1) lagoon fluxes. The overall average lagoon emission for H2S (0.038 g day−1 AU−1) was also approximately an order of magnitude higher than the overall average DMS (0.0034 g day−1 AU−1) and DMDS (0.0028 g day−1 AU−1) emissions. H2S, DMS and DMDS have offensive odors and low odor thresholds. Over all four sampling seasons, 77% of 15 min averaged H2S barn concentrations were an order of magnitude above the average odor threshold. During these sampling periods, however, DMS and DMDS concentrations did not exceed their odor thresholds. The overall average barn and lagoon emissions from this study were used to help estimate barn, lagoon and total (barn + lagoon) RSC emissions from swine CAFOs in North Carolina. Total (barn + lagoon) H2S emissions from swine CAFOs in North Carolina were estimated to be 1.22*106 kg yr−1. The barns had significantly higher H2S emissions than the lagoons, contributing ≈98% of total North Carolina H2S swine CAFO emissions. Total (barn + lagoon) emissions for DMS and DMDS were 1–2 orders of magnitude lower, with barns contributing ≈86% and ≈93% of total emissions, respectively. H2S swine CAFO emissions were estimated to contribute ≈18% of North Carolina H2S emissions.

New Proteins Involved in Sulfur Trafficking in the Cytoplasm of Allochromatium vinosum

The formation of periplasmic sulfur globules is an intermediate step during the oxidation of reduced sulfur compounds in various sulfur-oxidizing microorganisms. The mechanism of how this sulfur is activated and crosses the cytoplasmic membrane for further oxidation to sulfite by the dissimilatory reductase DsrAB is incompletely understood, but it has been well documented that the pathway involves sulfur trafficking mediated by sulfur-carrying proteins. So far sulfur transfer from DsrEFH to DsrC has been established. Persulfurated DsrC very probably serves as a direct substrate for DsrAB. Here, we introduce further important players in oxidative sulfur metabolism; the proteins Rhd_2599, TusA, and DsrE2 are strictly conserved in the Chromatiaceae, Chlorobiaceae, and Acidithiobacillaceae families of sulfur-oxidizing bacteria and are linked to genes encoding complexes involved in sulfur oxidation (Dsr or Hdr) in the latter two. Here we show via relative quantitative real-time PCR and microarray analysis an increase of mRNA levels under sulfur-oxidizing conditions for rhd_2599, tusA, and dsrE2 in Allochromatium vinosum. Transcriptomic patterns for the three genes match those of major genes for the sulfur-oxidizing machinery rather than those involved in biosynthesis of sulfur-containing biomolecules. TusA appears to be one of the major proteins in A. vinosum. A rhd_2599-tusA-dsrE2-deficient mutant strain, although not viable in liquid culture, was clearly sulfur oxidation negative upon growth on solid media containing sulfide. Rhd_2599, TusA, and DsrE2 bind sulfur atoms via conserved cysteine residues, and experimental evidence is provided for the transfer of sulfur between these proteins as well as to DsrEFH and DsrC.

Effects of sorbent materials on the cryofocusing analysis of gaseous reduced sulphur compounds

The relative performance of different sorbent materials employed in the cryofocusing (e.g. in cold trap (CT) unit) stage was investigated at sub-ambient temperature by the thermal desorption (TD)–gas chromatography (GC)–pulsed flame photometric detector. To this end, the TD-based calibration of five reduced sulphur compounds (RSC: H 2S, CH 3SH, CS 2, DMS and DMDS) and SO 2 was carried out via the Peltier cooling system with five types of sorbent combinations such as two single-bed (Tenax TA and Silica gel) plus three multibed types (a combination of either two from the following three sorbents: Tenax TA, Silica gel and Carbopack B). Relative performance of each of all five CT options, if evaluated in terms of response factors for each compound, demonstrated that each CT composition acts as an important criterion to distinguish detection properties between light and heavy sulphur species. Although the relative response of H 2S and CH 3SH was systematically distinguishable between the CT types, that of SO 2 was the most complicated to interpret. According to this study, the two CT types consisting of Carbopack B and Silica gel (CS-0.4 and CS-0.6) were the optimum choices for sulphur gas analysis in terms of basic QA parameters (sensitivity, reproducibility and linearity).

The gill chamber epibiosis of deep‐sea shrimp Rimicaris exoculata: an in‐depth metagenomic investigation and discovery of Zetaproteobacteria

The gill chamber of deep-sea hydrothermal vent shrimp Rimicaris exoculata hosts a dense community of epibiotic bacteria dominated by filamentous Epsilonproteobacteria and Gammaproteobacteria. Using metagenomics on shrimp from the Rainbow hydrothermal vent field, we showed that both epibiont groups have the potential to grow autotrophically and oxidize reduced sulfur compounds or hydrogen with oxygen or nitrate. For carbon fixation, the Epsilonproteobacteria use the reductive tricarboxylic acid cycle, whereas the Gammaproteobacteria use the Calvin-Benson-Bassham cycle. Only the epsilonproteobacterial epibionts had the genes necessary for producing ammonium. This ability likely minimizes direct competition between epibionts and also broadens the spectrum of environmental conditions that the shrimp may successfully inhabit. We identified genes likely to be involved in shrimp-epibiont interactions, as well as genes for nutritional and detoxification processes that might benefit the host. Shrimp epibionts at Rainbow are often coated with iron oxyhydroxides, whose origin is intensely debated. We identified 16S rRNA sequences and functional genes affiliated with iron-oxidizing Zetaproteobacteria, which indicates that biological iron oxidation might play a role in forming these deposits. Fluorescence in situ hybridizations confirmed the presence of active Zetaproteobacteria in the R. exoculata gill chamber, thus providing the first evidence for a Zetaproteobacteria-invertebrate association.

Abatements of reduced sulphur compounds, colour, and organic matter from indigo dyeing effluents by electrocoagulation

In the present study, the treatability of indigo dyeing effluents by the electrocoagulation (EC) process using stainless steel electrodes was experimentally investigated. The samples used were concentrated with main pollutant parameters of chemical oxygen demand (COD) (1000–1100 mg/L), reduced sulphur species (over 2000 mg , and colour (0.12–0.13 1/cm). The study focused on the effect of main operation parameters on the EC process performance in terms of abatement of reduced sulphur compounds as well as decolourization and organic matter reduction. Results indicated that the performance of EC proved to be high providing total oxidation of the reduced sulphur compounds, almost complete decolourization, and COD removal up to 90%. Increasing applied current density from 22.5 to 45 mA/cm2 appreciably improved abatement of the reduced sulphur compounds for Sample I, but a further increase in the applied current density to 67.5 mA/cm2 did not accelerate the conversion rate to sulphate. The process performance was adversely affected by increasing initial concentration of the reduced sulphur compounds. Decolourization and organic matter removal efficiency enhanced with increasing applied current density. The main removal mechanism of the reduced sulphur compounds by EC was explained as conversion to sulphate via oxidation. Conversion rate to sulphate fitted pseudo-first-order kinetics very well.

Effect of redox potential on heavy metals and As behavior in dredged sediments

The effect of redox changes with respect to mobility of Cr, Cu, Pb, Zn, and As in five dredged sediments originating from disposal sites in the Netherlands was studied in the paper. An extraction procedure with a neutral unbuffered salt solution (0.01M CaCl2) was used to investigate the behavior of heavy metals and As in laboratory-based batch experiments conducted under oxidized and reduced redox conditions and carried out for 21 d. An increase in the redox potential (above +400 mV up to +503 mV) resulted in a rise of solubility of heavy metals in all sediments. However, at low redox potentials, an increase in As concentration was observed in the highly As-contaminated sediment. Mass balances were performed to follow the use of oxygen and the production of CO2, NO3-, SO42- and PO43-. An increase in redox potential has a large effect (40–80%) on the oxidation of reduced sulfur compounds to SO42-. Such increase in redox potential led to a solubilization of only about 1% of Cr, Cu, Pb, and Zn. Still, such low solubilization of these heavy metals leads to an increase of significance of the issue concerning ground and surface water quality.

A Comparative Quantitative Proteomic Study Identifies New Proteins Relevant for Sulfur Oxidation in the Purple Sulfur Bacterium Allochromatium vinosum

In the present study, we compared the proteome response of Allochromatium vinosum when growing photoautotrophically in the presence of sulfide, thiosulfate, and elemental sulfur with the proteome response when the organism was growing photoheterotrophically on malate. Applying tandem mass tag analysis as well as two-dimensional (2D) PAGE, we detected 1,955 of the 3,302 predicted proteins by identification of at least two peptides (59.2%) and quantified 1,848 of the identified proteins. Altered relative protein amounts (≥1.5-fold) were observed for 385 proteins, corresponding to 20.8% of the quantified A. vinosum proteome. A significant number of the proteins exhibiting strongly enhanced relative protein levels in the presence of reduced sulfur compounds are well documented essential players during oxidative sulfur metabolism, e.g., the dissimilatory sulfite reductase DsrAB. Changes in protein levels generally matched those observed for the respective relative mRNA levels in a previous study and allowed identification of new genes/proteins participating in oxidative sulfur metabolism. One gene cluster (hyd; Alvin_2036-Alvin_2040) and one hypothetical protein (Alvin_2107) exhibiting strong responses on both the transcriptome and proteome levels were chosen for gene inactivation and phenotypic analyses of the respective mutant strains, which verified the importance of the so-called Isp hydrogenase supercomplex for efficient oxidation of sulfide and a crucial role of Alvin_2107 for the oxidation of sulfur stored in sulfur globules to sulfite. In addition, we analyzed the sulfur globule proteome and identified a new sulfur globule protein (SgpD; Alvin_2515).

Involvement of Salicylic Acid in Sulfur Induced Salinity Tolerance: A Role of Glutathione

Plants are severely affected by salinity due to its high magnitude of adverse impacts and worldwide distribution. Among various strategies, nutrient management may be an important aspect in alleviating stress under varied environmental conditions. The uptake and assimilation of sulfur plays an inevitable and imperative role in determining plant growth and development and is a fundamental part of several important compounds, such as glutathione, co-enzymes, vitamins, phytohormones and reduced sulfur compounds that decipher growth and vigour of plants under optimal and stressful environments. Assimilatory sulfate reduction may induce salt tolerance by coordinating various physiological processes and molecular mechanisms which are likely to be induced b y phytohormones. Among phytohormones salicylic acid (SA) could provide tolerance against salinity stress by enhancing physiological processes and can improve salinity tolerance by its effect on sulfur assimilation pathway as biochemically or molecular mechanisms. The present review critically evaluates the recent studies on the modulation of sulfur assimilation and gives an insight into the role of glutathione to maintain redox state and their cumulative significance in plants’ tolerance to salinity by SA in inducing various physiological responses in plants under salinity stress.

Treatment Efficiency by means of a Nonthermal Plasma Combined with Heterogeneous Catalysis of Odoriferous Volatile Organic Compounds Emissions from the Thermal Drying of Landfill Leachates

The objective of the present work was to assess the odoriferous volatile organic compounds depuration efficiency of an experimental nonthermal plasma coupled to a catalytic system used for odor abatement of real emissions from a leachate thermal drying plant installed in an urban solid waste landfill. VOC screening was performed by means of HRGC-MS analysis of samples taken at the inlet and at the outlet of the nonthermal plasma system. Odor concentration by means of dynamic olfactometry, total organic carbon, mercaptans, NH3, and H2S were also determined in order to assess the performance of the system throughout several days. Three plasma frequencies (100, 150, and 200 Hz) and two catalyst temperatures (150°C and 50°C) were also tested. Under conditions of maximum capacity of the treatment system, the results show VOC depuration efficiencies around 69%, with average depuration efficiencies between 44 and 95% depending on the chemical family of the substance. Compounds belonging to the following families have been detected in the samples: organic acids, alcohols, ketones, aldehydes, pyrazines, and reduced sulphur compounds, among others. Average total organic carbon removal efficiency was 88%, while NH3and H2S removal efficiencies were 88% and 87%, respectively, and odor concentration abatement was 78%.