Sulfide Production Research Articles

Gut microbiome signatures reflect different subtypes of irritable bowel syndrome

ABSTRACT Irritable bowel syndrome (IBS) is a heterogeneous condition with multifactorial pathogenesis. We studied deeply phenotyped individuals with microbiota sequencing enrolled in the American Gut Project. The IBS subjects were matched by age, gender, body mass index, geography, and dietary patterns with non-IBS controls. A total of 942 subjects with IBS-Diarrhea (IBS-D), IBS-Constipation (IBS-C), unclassified IBS (IBS-U), and 942 non-IBS controls were included. We compared taxonomic and functional composition of gut microbiota based on 16S sequencing data and linked them with clinical characteristics and dietary factors. Subjects with IBS-D or IBS-U but not IBS-C showed significantly reduced bacterial diversity (Shannon; p < .01). Distinct bacterial signatures were associated with different IBS subtypes, and the related functional changes were related to IBS pathogenesis, such as the increased hydrogen sulfide production pathway in IBS-D and the increased palmitoleate biosynthesis pathway in IBS-C. IBS subjects with depression showed lower abundance of Bifidobacterium, Sutterella, Butyricimonas and higher abundance of Proteus than those without depression. The relative abundance of microbial short-chain fatty acid production pathways was significantly lower in IBS patients with depression than those without depression in all three subtypes. Female, younger age in IBS-D, and older age in IBS-C were associated with more severe microbiota dysbiosis, and distinct dietary factors had significant effects on the gut microbiota in different IBS subtypes. Our analysis identified the compositional uniqueness of gut microbiota in different IBS subtypes. Distinct associations of the gut microbiota with depression in IBS provide insights into shared pathways in disease pathogenesis. These findings highlight the importance of personalized gut microbiome modulation approaches in different subtypes for optimal therapeutic effects.

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.

Salinization of coastal saline-alkali soil might enhance H2S release by affecting H2S-related bacterial communities

Bacterial metabolism can result in the production and release of hydrogen sulfide (H2S), a reductive gas, in soils. Hydrogen sulfide-releasing bacteria (HSRB) assimilate organic sulfur or dissimilate sulfate to generate and release H2S, whereas H2S-oxidizing bacteria (HSOB) oxidize H2S generated by themselves or other bacteria to soluble sulfate resulting in sulfur retention in soil. However, the effects environmental factors such as electrical conductivity on both these bacterial groups and H2S release remain unclear; some key processes such as H2S oxidation also remain underexplored. In this study, we found that high electrical conductivity in coastal saline-alkali soil affects these bacterial communities, especially HSRB, potentially enhancing H2S release. The “sink” of H2S gas, represented by sulfidic sulfur (concentration, 0.2–3.4 nmol/g) in coastal saline-alkali and inland soils, was determined using the methylene blue method, and found to be positively correlated with soil electrical conductivity, suggesting that more H2S gas potentially volatilized from salinized soil. We then revealed that the proportion of HSRB clones was correlated positively and significantly with the electrical conductivity and sulfidic sulfur of soil, but not with the pH or sulfur source. Further, 16S rRNA gene sequence comparison indicated significantly reduced richness and diversity of bacterial communities and considerably altered the composition of dominant bacterial populations in coastal saline-alkali soil. The phyla Proteobacteria, Bacteroidetes, and Gemmatimonadetes accounted for 38 %, 30.1 %, and 11.1 % and for 28 %, 12.9 %, and 2.5 % of the bacterial populations in coastal saline-alkali and inland soil, respectively. PICRUSt analysis showed that the richness of genes encoding the key H2S oxidation enzymes, sulfide:quinone reductase and sulfate hydrolase, was decreased significantly and negatively correlated with the detected sulfidic sulfur. These enzymes are usually expressed by HSOB in coastal saline-alkali soil, implying a low sulfide oxidation capacity. These results indicate that the number of HSRB is increased whereas the ability of H2S oxidation is decreased in coastal saline-alkali soil, which might lead to enhanced H2S release. Overall, this study provides new insights for understanding the sulfur biological cycle in saline-alkali soils.

Biogeochemical impacts of fish farming on coastal sediments: Insights into the functional role of cable bacteria.

Fish farming in sea cages is a growing component of the global food industry. A prominent ecosystem impact of this industry is the increase in the downward flux of organic matter, which stimulates anaerobic mineralization and sulfide production in underlying sediments. When free sulfide is released to the overlying water, this can have a toxic effect on local marine ecosystems. The microbially-mediated process of sulfide oxidation has the potential to be an important natural mitigation and prevention strategy that has not been studied in fish farm sediments. We examined the microbial community composition (DNA-based 16S rRNA gene) underneath two active fish farms on the Southwestern coast of Iceland and performed laboratory incubations of resident sediment. Field observations confirmed the strong geochemical impact of fish farming on the sediment (up to 150 m away from cages). Sulfide accumulation was evidenced under the cages congruent with a higher supply of degradable organic matter from the cages. Phylogenetically diverse microbes capable of sulfide detoxification were present in the field sediment as well as in lab incubations, including cable bacteria (Candidatus Electrothrix), which display a unique metabolism based on long-distance electron transport. Microsensor profiling revealed that the activity of cable bacteria did not exert a dominant impact on the geochemistry of fish farm sediment at the time of sampling. However, laboratory incubations that mimic the recovery process during fallowing, revealed successful enrichment of cable bacteria within weeks, with concomitant high sulfur-oxidizing activity. Overall our results give insight into the role of microbially-mediated sulfide detoxification in aquaculture impacted sediments.

Environmental changes affect the microbial release of hydrogen sulfide and methane from sediments at Boknis Eck (SW Baltic Sea).

Anthropogenic activities are modifying the oceanic environment rapidly and are causing ocean warming and deoxygenation, affecting biodiversity, productivity, and biogeochemical cycling. In coastal sediments, anaerobic organic matter degradation essentially fuels the production of hydrogen sulfide and methane. The release of these compounds from sediments is detrimental for the (local) environment and entails socio-economic consequences. Therefore, it is vital to understand which microbes catalyze the re-oxidation of these compounds under environmental dynamics, thereby mitigating their release to the water column. Here we use the seasonally dynamic Boknis Eck study site (SW Baltic Sea), where bottom waters annually fall hypoxic or anoxic after the summer months, to extrapolate how the microbial community and its activity reflects rising temperatures and deoxygenation. During October 2018, hallmarked by warmer bottom water and following a hypoxic event, modeled sulfide and methane production and consumption rates are higher than in March at lower temperatures and under fully oxic bottom water conditions. The microbial populations catalyzing sulfide and methane metabolisms are found in shallower sediment zones in October 2018 than in March 2019. DNA-and RNA profiling of sediments indicate a shift from primarily organotrophic to (autotrophic) sulfide oxidizing Bacteria, respectively. Previous studies using data collected over decades demonstrate rising temperatures, decreasing eutrophication, lower primary production and thus less fresh organic matter transported to the Boknis Eck sediments. Elevated temperatures are known to stimulate methanogenesis, anaerobic oxidation of methane, sulfate reduction and essentially microbial sulfide consumption, likely explaining the shift to a phylogenetically more diverse sulfide oxidizing community based on RNA.

Study on deposit formation model in sulfide-containing natural gas environment

The breathing pipe of a produced water storage tank in a sulfide-containing natural gas station is prone to deposit formation, which leads to pipeline blockage. In this study, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses of the deposit in breathing pipe show that the deposit is composed of elemental sulfur and corrosion scales of ferrous polysulfide and ferrous sulfate. Existing deposit formation prediction models cannot predict the formation of elemental sulfur and corrosion scales in sulfide-containing environments. Herein, based on thermodynamic models of elemental sulfur and corrosion scale formation, deposit formation models of elemental sulfur, ferrous polysulfide, and ferrous sulfate scale formation are established. It is found that deposition of elemental sulfur and ferrous polysulfide increases with decreasing temperature of the breathing tube. Corrosion of pipe in the precipitating corrosive water leads to higher activity of left[{mathrm{Fe}}^{2+}right] on the inner wall of the pipe carried by the sulfide-containing natural gas. Consequently, ferrous polysulfide and ferrous sulfate are easily deposited when the activity products of ferrous, sulfide, and sulfate ions are higher than the thermodynamic solubility product constant. The aforementioned prediction models are applied to predict the deposition of ferrous polysulfide, ferrous sulfate corrosion scale, and elemental sulfur using the chemical composition data of gas and precipitating water in the breathing pipe of the produced water tank of TB101-X1 well. The prediction results of the models are consistent with those of actual chemical composition analysis, which verifies the accuracy and reliability of the models.

Natural formation of copper sulfide nanoparticles via microbially mediated organic sulfur mineralization in soil: Processes and mechanisms

Sulfur cycling is known to control the speciation and bioavailability of copper in the environment via inorganic sulfur oxidation and reduction. However, it remains unclear how the mineralization of organic sulfur and associated microbial processes affect Cu transformations. This study discovered a neglected mechanism that mediates Cu mobility and speciation via cysteine mineralization in a paddy soil. We provide evidence for a pathway of sulfide production from cysteine via indigenous soil microorganisms. The produced sulfide promotes the formation of copper sulfide nanoparticles, constituting an alternative copper sulfide formation mechanism that bypasses sulfate reduction. A bacterium isolated from the soil, named Bacillus sp. TR1, played a role in forming cell-associated copper sulfide nanoparticles. A metagenomics approach was applied to detect genes related to cysteine mineralization (dcyD, CTH, CBS, and sseA) and the associated microbes in the soil. The sseA gene was most abundant, and the microorganisms involved in cysteine mineralization were taxonomically diverse, including members of phyla Proteobacteria, Firmicutes, and Thaumarchaeota. Geobacter, Sulfuriferula, Nitrososphaera, Noviherbaspirillum, and Clostridium were the dominant genera with potential to metabolize cysteine to form copper sulfide nanoparticles. Our study not only provides initial molecular-level insights into the abundance, diversity, and metabolism of cysteine-mineralizing microorganisms but also highlights their important ecological functions in metal and sulfur biogeochemical cycles.

Study of the effect of protein synthesis inhibitors on growing &lt;i&gt;Escherichia coli&lt;/i&gt; bacteria using electrochemical sensors

Background. The study of the mechanisms of action of antibiotics requires the integrated use of traditional microbiological and physicochemical methods. The aim. To study the response of Escherichia coli bacteria to the action of four antibiotics, inhibitors of protein synthesis, using combined approach. Methods. Bacteria were grown under aerobic conditions on minimal M9 medium with glucose. Tetracycline, kanamycin, streptomycin and chloramphenicol have been tested. The effect of antibiotics on survival (CFU) and growth rate was determined. Respiratory activity, sulfide production, extracellular potassium, as well as pH and Eh of the medium were measured using electrochemical sensors directly in a growing culture in the “real time”, membrane potential was measured using a DiBAC dye and a Leica DM2000 fluorescent microscope. Results. The tested antibiotics were divided into two groups according to their properties. Tetracycline and chloramphenicol showed a pronounced bacteriostatic effect, growth inhibition began immediately after the addition of antibiotics and occurred at a high rate. Both antibiotics inhibited respiration, stimulated sulfide production and an Eh jump. Bacteria treated with tetracycline and chloramphenicol retained the ability to maintain membrane potential and intracellular potassium better. Inhibition of respiration led to a decrease in glucose catabolism, as evidenced by a lower rate of acidification of the medium compared to the control. Growth inhibition with streptomycin and kanamycin was initiated with a 30-minute delay. Both antibiotics showed a bactericidal effect, did not stimulate sulfide production and Eh jump, did not inhibit respiration, but caused a drop in membrane potential and intracellular potassium. High respiratory activity promoted glucose catabolism, as evidenced by the rapid acidification of the medium. Of interest is the detection of kanamycin-induced sulfide production during E. coli growth on MOPS medium. Conclusion. An analysis of the data obtained indicates that the use of electrochemical sensors in combination with traditional methods is a promising approach to studying the mechanisms of action of antibiotics.

Guar Gum Stimulates Biogenic Sulfide Production in Microbial Communities Derived from UK Fractured Shale Production Fluids.

Shale gas production fluids offer a window into the engineered deep biosphere. Here, for the first time, we report on the geochemistry and microbiology of production fluids from a UK shale gas well in the Bowland shale formation. The composition of input fluids used to fracture this well were comparatively lean, consisting only of water, sand, and polyacrylamide. This formation therefore represents an interesting comparison to previously explored fractured shales in which more additives were used in the input fluids. Here, we combine cultivation and molecular ecology techniques to explore the microbial community composition of hydraulic fracturing production fluids, with a focus on the potential for common viscosity modifiers to stimulate microbial growth and biogenic sulfide production. Production fluids from a Bowland Shale exploratory well were used as inocula in substrate utilization experiments to test the potential for polyacrylamide and guar gum to stimulate microbial metabolism. We identified a consortium of thiosulfate-reducing bacteria capable of utilizing guar gum (but not polyacrylamide), resulting in the production of corrosive and toxic hydrogen sulfide. Results from this study indicate polyacrylamide is less likely than guar gum to stimulate biogenic sulfide production during shale gas extraction and may guide planning of future hydraulic fracturing operations. IMPORTANCE Shale gas exploitation relies on hydraulic fracturing, which often involves a range of chemical additives in the injection fluid. However, relatively little is known about how these additives influence fractured shale microbial communities. This work offers a first look into the microbial community composition of shale gas production fluids obtained from an exploratory well in the Bowland Shale, United Kingdom. It also seeks to establish the impact of two commonly used viscosity modifiers, polyacrylamide and guar gum, on microbial community dynamics and the potential for microbial sulfide production. Not only does this work offer fascinating insights into the engineered deep biosphere, it could also help guide future hydraulic fracturing operations that seek to minimize the risk of biogenic sulfide production, which could reduce efficiency and increase environmental impacts of shale gas extraction.

Metagenomics analysis of ecosystem integrating methane and sulfide generation in urban sewer systems

Simultaneous generation of methane and sulfide is a major concern affecting sewer system operations, and the methanogenic archaea and sulfate-reducing bacteria may increase methane and sulfide production via their symbiotic activities. However, interactions between methane and sulfide metabolism are unclear. In this study, 18 high-quality draft genomes from sewer biofilms were obtained via genome-resolved metagenomics (Binning). The assembled bins 1, 5, 10, 12 and 15 contained abundant ackA, mcrA, mtsA, mtsB and serA genes were involved in methane generation, sulfide consumption via methane metabolism and sulfide metabolism to promote methane generation. Because of the independent and single functionality of these bins, they formed a bio-symbiotic system to promote methane and sulfide generation. Interestingly, for bins 2, 3, 8 and 9, the functions of methane generation, sulfide generation and sulfide consumption via methane metabolism occurred simultaneously. The community affiliations of the assembled bins were also unusual. For instance, bin 9 (Ignavibacteria bacterium) was derived from the Ignavibacteriae supercluster that was not been detected in sewer biofilms, but participated in both methane generation and sulfide consumption. Therefore, these bins formed another biological system with multiple functional aggregates. Two types of ecosystems integrating methane and sulfide generation in sewers were proposed. Our results improve the understanding of toxic gas emissions in sewers and provide a theoretical foundation for studies on gas suppression.

Effect of Sulfate-Reducing Bacteria on the Production of Iron Sulfides

Using Fourier transform infrared spectroscopy (FTIR) to identify the sulfate-reducing bacteria (SRB) in Daqing Oilfield sewage. The growth curve of SRB and the adsorption ability of extracellular polymeric substances (EPS) to the Fe2+ were combined to explore iron sulfide generation. X-ray diffraction (XRD) results showed that different species of SRB produce iron sulfides, mainly composed of mackinawite. The growth characteristics of SRB affected the formation of iron sulfides and had a negative charge. Various SRB growth trends were different. The growth of the bacterium in an exponential phase or log phase can be described by the greater concentration of inoculation. And smooth growth trends were contributed to the formation of FeS. At the same time, sulfur-rich, like FeS2, was easily formed when S2− (or S2 2−) played a major role compared with the protein and polysaccharide functional groups in the negatively charged EPS at the process of Fe2+ adsorption.

Complex inhibitions on anaerobic degradation of monosodium glutamate in wastewater under low COD/sulfate ratios

To investigate the complex inhibitions leading to the deterioration of reactor performance in anaerobic treatment of monosodium glutamate (MSG) wastewater under low COD/sulfate ratios, a comprehensive assessment of the overall reactor performance, sludge characteristics and microbial community characteristics was conducted in this study. The COD removal rate of the reactor was maintained above 90% throughout the experiment, but the gas yield decreased by 52% due to the complex competition between sulfate-reducing bacteria (SRB) and methane-producing archaea (MPA) resulting in a decreasing number of MPA. The sludge characteristics and microbial community features indicated that the complex competition between SRB and MPA included competition for hydrogen and survival space in the reactor. In addition, the competitive advantage of SRB for electrons led to the production of more sulfides in the reactor, further inhibiting the activity of MPA. Therefore, the complex inhibition within the reactor for anaerobic treatment of MSG wastewater with low COD/sulfate ratios, including sulfide toxicity inhibition, competition between SRB and MPA for substrate and space, not only led to a reduction in gas production, but also affected microbial activity and glutamate degradation.

Early diagenetic processes in an iron-dominated marine depositional system

The early diagenetic interplay between reactive iron, sulfur, and organic matter in the bathymetrically isolated Santa Monica Basin (SMB) sediments are investigated in this study. We explore solid-phase and porewater profiles from the basin, supplemented with a transect from 71 to 907 m water depth that includes oxygenated (>60 μM O2) bottom waters near the coast and oxygen-deficient waters (∼4 µM O2) in the basin. The geochemical data of the basin sediments are further scrutinized by means of reactive transport modeling.The results show that the basin sediments do not follow the traditional geochemical signatures of oxygen-deficient settings. A lack of dissolved sulfide accumulation and sulfurized iron persists despite the sediments being deposited under reducing conditions (without bioturbation/bioirrigation), strong organic carbon input (TOC up to 5.0 wt%), and active dissimilatory sulfate reduction. Not only did we find an exceptional enrichment in highly reactive Fe in the surface sediments (∼45 % of total Fe), but the enrichment of reactive Fe, including ferrihydrite, persists downcore and coexists with high levels of dissolved Fe. The enhanced preservation of Fe oxides and lack of iron-sulfide precipitation is in part explained by detection via Mössbauer spectra of iron oxides bounded to organic matter (Fe[III]-OM coprecipitates).The modeled Fe budget shows that most of the Fe oxides in the surface sediments are internally recycled by upward diffusion and subsequent oxidation of Fe2+. Sulfide oxidation coupled to Fe reduction effectively precludes sulfide accumulation while enhancing build-up of dissolved Fe, fueling the Fe cycle within the first 5 cm depth. Continuous reoxidation of Fe2+ enhances the formation of Fe(III)-OM coprecipitates, limiting the amount of reactive organic matter. In the unavailability of labile organic matter, other than within the uppermost layers, the organic-rich sediment profiles are dominated by Fe cycling that limits the production and preservation of sulfides and enhances the preservation of Fe oxides and organic carbon. This study highlights key local controls on Fe availability in marginal basins and describes an intricate biogeochemical C-Fe-S cycling in modern and possibly ancient marine systems with important implications for Fe availability in the marine realm.

Application of different packing media for the biofiltration of gaseous effluents from waste composting

ABSTRACT A pilot-scale experiment was implemented in a waste bioreactor with an inner capacity of 1 m3 in order to simulate a real-scale composting process. The waste underwent composting conditions that are typical of the initial bio-oxidation phase, characterised by a high production of volatile organic compounds (VOCs), hydrogen sulphide (H2S) and odorants. The waste bioreactor was fed with an intermittent airflow rate of 6 Nm3/h. The target of this study was to investigate the air treatment performance of three biofilters with the same size, but filled with different filtering media: (1) wood chips, (2) a two-layer combination of lava rock (50%) and peat (50%), and (3) peat only. The analyses on air samples taken upstream and downstream of the biofilters showed that the combination of lava rock and peat presents the best performance in terms of mean removal efficiency of odour (96%), total VOCs (95%) and H2S (77%) concentrations. Wood chips showed the worst abatement performance, with respective mean removal efficiencies of 90%, 88% and 62%. From the results obtained, it is possible to conclude that the combination of lava rock and peat can be considered as a promising choice for air pollution control in waste composting facilities.

Environmentally friendly, non-glove box, closed-system and continuously massive production of lithium sulfide for battery applications

Lithium sulfide (Li2S) is an important material for lithium-sulfur batteries and solid-state batteries. However, its prohibitive price hinders the practical development of these technologies, reflecting multiple problems in existing production processes including high temperature/energy demands, greenhouse gas emissions, low yield, low purity and the use of air sensitive equipment. Herein we report the development of an environmentally friendly process for the scalable production of Li2S without need for a glove box. The net chemical process is the reaction between Li metal and hydrogen sulfide (H2S) with ethanol as the auxiliary solvent, which can in principle be recovered and recycled. The production capability reaches 1.0 kg_Li2S/day, 50–100 times greater than the largest scale reported in the literature. The material quality of the resulting Li2S is validated through its use as a cathode material in lithium-sulfur batteries, achieving essentially comparable performance with commercial Li2S. Moreover, additional value is provided by concomitant H2 production which is demonstrated through its use for the in-situ reduction of copper oxide. We believe that the process described by this work can be readily adapted to support the developments of advanced batteries.

Nitric Oxide Scavenging and Hydrogen Sulfide Production Synergistically Treat Rheumatoid Arthritis.

To restore the disordered endogenous gas levels is an efficient alternative for the treatment of rheumatoid arthritis (RA). Both insufficient hydrogen sulfide (H2 S) and excessive nitric oxide (NO) contribute to synovial inflammation. Herein, a new block polymer PEG10 -b-PNAPA30 -b-PEG10 composed of an NO-responsive monomer and a cysteine-triggered H2 S donor, which can simultaneously scavenge NO and release therapeutic H2 S for RA treatment, is reported. In vitro experiments demonstrate that the polymer exhibits a synergistic effect on suppressing reactive oxygen species levels and pro-inflammatory cytokine production via NF-κB signaling pathway. It leads to the polarization of macrophages from M1 to M2 phenotype. Moreover, the released H2 S further restrains NO production by suppressing the expression of iNOS. In vivo experiments with an RA rat model show that the system markedly mitigates the synovial inflammation, osteoporosis, and clinical symptoms of RA rats, which is attributed to the combination therapy of H2 S release and NO depletion. This work provides new insight into the synergistic treatment of RA and endogenous gas-related diseases.

Abstract 9410: Cardiovascular Disease Associated Metabolites TMA and TMAO Bind to Cystathionine Gamma-Lyase and Repress Its Enzymatic Production of Hydrogen Sulfide

While the causative factors of smoking and hypertension leading to cardiovascular disease (CVD) are well understood, those involved with diet-induced CVD are not. One metabolite regulated by diet that is involved with cardio-protection and vasodilation is the gasotransmitter hydrogen sulfide (H 2 S). However, the molecular inhibition of H 2 S-generating enzymes via CVD-inducing diets is not fully understood, nor is it known if this is the causative event leading to CVD. Enzymatic H 2 S production in mammalian tissues and cells is primarily via the transsulfuration enzymes cystathionine β-synthase (CBS) and cystathionine γ-lyase (CGL). A high fat Western diet contributes to CVD through gut microbiome metabolic pathways and subsequent host enzymes converting choline and carnitine into the metabolites trimethylamine (TMA) and trimethylamine-N-oxide (TMAO). We hypothesized that TMA and TMAO lower H 2 S production by directly interacting with CGL to reduce enzymatic activity and that these gut-related metabolites’ inhibition account for some of the CVD risks. Results: Using a lead acetate assay, we discovered that these metabolites reduce enzymatic H 2 S production in a CGL-dependent manner from tissues ex vivo as well as from purified human CGL in vitro to a similar extent as propargylglycine (PAG), a known CGL suicide inhibitor that also happens to be a bacterial metabolite. We found that in vivo , hepatic and renal H 2 S production increased in antibiotic treated mice surface plasma resonance (SPR) and micro-scale thermophoresis (MST) assays revealed direct and specific physical interactions between TMA and TMAO with CGL. Additionally, pre-incubation with PAG blocked the binding of TMAO with CGL, indicating that the mechanism and location of inhibition are shared. Conclusion: Diet-induced gut metabolites TMA and TMAO bind CGL enzyme and suppress enzymatic production of cardioprotective H 2 S.

Combined acute effect of salinity and substrate concentration on simultaneous sulfide and nitrite removal process

Nitrite or sulfide accumulation has always been a challenge for the treatment of saline or hypersaline wastewater. Simultaneous sulfide and nitrite removal process (SSNIR) targeting sulfide and nitrite as substrates, is a robust and potentially practical autotrophic denitrification biotechnology. Its feasibility to operate under hypersaline wastewater is not fully understood so far. Therefore, the current work explored the practicability of SSNIR to treat saline or hypersaline wastewater, evaluation of the toxicological effects of substrate and salinity on the denitrification and sulfide removal performance and product types. Additionally, the type of combined toxicity of substrate and salinity to SSNIR was determined. The results showed that the respective IC50 values for substrate shock on Specific sulfide oxidation activity (SSOA) and Specific denitrification activity (SDA) were 289.29 mg S/L and 300.92 mg S/L. The IC50 values of salinity shock on SSOA and SDA were 6.19 % wt (98.07 ms/cm) and 3.78 % wt (61.74 ms/cm), even the salinity level as high as 13.2 % wt (204 ms/cm) resulted in the reduction of 40 % nitrite removal efficiency. At salinity value>2.4 % wt (41 ms/cm), increase in salinity casted significantly positive effect on the nitrous oxide emission (P < 0.01). In addition, the combined salinity, substrate toxicity and salinity exposure value of<2.67 % wt (45 ms/cm) on SSNIR showed synergistic inhibition. A further increase in salinity (>45 ms/cm) alleviated the strength of synergistic inhibition and the effect on SSOA was identified as antagonistic inhibition.

Apatite in brachinites: Insights into thermal history and halogen evolution

Abstract Apatite is an important petrogenetic indicator in extraterrestrial materials. Here, we report the mineralogical features of apatite and associated phases in three brachinites Northwest Africa (NWA) 4969, NWA 10637, and NWA 11756. Two types of apatite are observed: intergranular apatite and apatite inclusion within chromite and silicate minerals. The intergranular chlorapatite is enclosed by or penetrated by irregular porous merrillite, indicating chlorapatite replacement by merrillite. The intergranular chlorapatite is closely associated with a fine-grained pyroxene-troilite intergrowth along olivine grain boundaries, which is a sulfidization product of olivine. High-Ca pyroxene is observed as a constituent phase in the intergrowth for the first time. The apatite inclusions are either monomineralic or closely associated with subhedral-euhedral pore-free merrillite. In NWA 4969, the apatite inclusions show a large compositional variation from chlorapatite to fluorapatite and are systematically more F-rich than intergranular apatite; while the apatite inclusions in NWA 10637 and NWA 11756 are chlorapatite. Most of the two apatite types in brachinites contain oriented tiny or acicular chromite grains, suggesting the exsolution of chromite from apatite. We propose that apatite replacement by merrillite, formation of pyroxene-troilite intergrowth, and exsolution of chromite in apatite were caused by a shock-induced, transient heating event (~930–1000 °C) on the brachinite parent body. This heating event resulted in halogen devolatilization during replacement of the intergranular apatite by merrillite, which probably disturbed the Mn-Cr isotopic system in brachinites as well. We also propose that the apatite inclusions could be a residual precursor material of the brachinites.

The potent effects of polyoxometalates (POMs) on controlling sulfide and methane production from sewers

Although the dose of biocides to sewers could control sulfide and methane production, the high resistance of sulfate-reducing bacteria (SRB) to biocides would increase dosing frequency and thereby enlarge chemical costs. Polyoxometalates (POMs, Group VI oxyanion), as a specific inhibitor of SRB, has been applied for sulfide control in oil fields and anaerobic digesters, but not demonstrated in sewers. This study filled such knowledge gap and investigated its feasibility for methane alleviation. Long-term monitoring demonstrated that one-time dosing of 2 mM POMs into sewers immediately reduced sulfide production by >90 %. And the time for recovering 50 % sulfide production was beyond 20 days, which was much more outstanding than other chemicals. POMs combined with a low level of free nitrous acid (0.045 mg-N/L) could overcome the relatively low methane control of the single POMs dosing, with 80 % suppression of methanogenic activity for 30 days. Meanwhile, the POMs-based strategy reduced the average organic carbon loss by 18 %. Furthermore, the beneficial side-effect of in-sewer POMs-dosing on downstream nitrogen removal could be achieved with the confluence of sewage. Model-analysis indicated the recovery of sulfide and methane was a re-formation process of biofilms. Mechanistic study elucidated POMs broke the extracellular polymeric substances of biofilms and damaged the cell membranes due to accumulations of intracellular reactive oxygen species. This suppressed microbial metabolic activities including organics dehydrogenation, energy provision and electron transfer processes, and inhibited key enzymatic activities. Microbial community analysis suggested POMs shifted microbes towards against hydrolysis, acidogenesis, dissimilatory sulfate reduction and methanogenesis. Further, predicted functional genes revealed that metabolic pathways were mostly down-regulated by POMs. This study provided a better understanding for controlling sulfide and methane in sewers using biocides.