Activity Of Sulfate-reducing Bacteria Research Articles

Mercury supply limits methylmercury production in paddy soils

The neurotoxic methylmercury (MeHg) is a product of inorganic mercury (IHg) after microbial transformation. Yet it remains unclear whether microbial activity or IHg supply dominates Hg methylation in paddies, hotspots of MeHg formation. Here, we quantified the response of MeHg production to changes in microbial activity and Hg supply using 63 paddy soils under the common scenario of straw amendment, a globally prevalent agricultural practice. We demonstrate that the IHg supply is the limiting factor for Hg methylation in paddies. This is because IHg supply is generally low in soils and can largely be facilitated (by 336–747 %) by straw amendment. The generally high activities of sulfate-reducing bacteria (SRB) do not limit Hg methylation, even though SRB have been validated as the predominant microbial Hg methylators in paddies in this study. These findings caution against the mobilization of legacy Hg triggered by human activities and climate change, resulting in increased MeHg production and the subsequent flux of this potent neurotoxin to our dining tables.

Multi-approach assessment of groundwater biogeochemistry: Implications for the site characterization of prospective spent nuclear fuel repository sites

The disposal of spent nuclear fuel in deep subsurface repositories using multi-barrier systems is considered to be the most promising method for preventing radionuclide leakage. However, the stability of the barriers can be affected by the activities of diverse microbes in subsurface environments. Therefore, this study investigated groundwater geochemistry and microbial populations, activities, and community structures at three potential spent nuclear fuel repository construction sites. The microbial analysis involved a multi-approach including both culture-dependent, culture-independent, and sequence-based methods for a comprehensive understanding of groundwater biogeochemistry. The results from all three sites showed that geochemical properties were closely related to microbial population and activities. Total number of cells estimates were strongly correlated to high dissolved organic carbon; while the ratio of adenosine-triphosphate:total number of cells indicated substantial activities of sulfate reducing bacteria. The 16S rRNA gene sequencing revealed that the microbial communities differed across the three sites, with each featuring microbes performing distinctive functions. In addition, our multi-approach provided some intriguing findings: a site with a low relative abundance of sulfate reducing bacteria based on the 16S rRNA gene sequencing showed high populations during most probable number incubation, implying that despite their low abundance, sulfate reducing bacteria still played an important role in sulfate reduction within the groundwater. Moreover, a redundancy analysis indicated a significant correlation between uranium concentrations and microbial community compositions, which suggests a potential impact of uranium on microbial community. These findings together highlight the importance of multi-methodological assessments in better characterizing groundwater biogeochemical properties for the selection of potential spent nuclear fuel disposal sites.

Anomalous Gold Concentrations in Hypersaline Wetland Sediments (Laguna Honda, South Spain) Caused by Nanoparticles Used in Agricultural Practices: Environmental Transformation.

Illite-rich sediments from the Laguna Honda wetland, an eutrophicated hypersaline wetland with waters enriched in Mg and Ca surrounded by olive groves in the Guadalquivir Basin River (South Spain), are polluted by elevated concentrations of gold (up to 21.9 ppm) due to agricultural practices. The highest gold contents appear in the shore sediments of the lake, where up to 20 µm homoaggregates of fused gold nanoparticles (AuNp) are found. Small nanoaggregates of up to six fused gold nanoparticles and very few isolated nanoparticles around 1 nm in size can also be observed to form heteroaggregates of AuNp-mica, especially in the deeper sediments in the central part of the wetland, where Au concentrations are lower (up to 1.89 ppm). The high nanoparticle concentration caused by the inappropriate application of pesticides favors nanoparticle collision in the wetland's Mg- and Ca-rich waters and the fast coagulation and deposition of Au homoaggregates in the gold-rich shore sediment of the lake. The interaction of gold nanoparticles with the abundant illite particles in the wetland's hypersaline waters promotes the simultaneous formation of low-density Au-illite heteroaggregates, which are transported and deposited in the less-rich-in-gold sediments of the central part of the lake. The small sizes of the isolated AuNp and AuNp-fused contacts of the aggregates suggest modifications in the original nanoparticles involving dissolution processes. The presence of bacterial communities resistant to heavy metal stress (Luteolibacter and Maricaulis), as well as the activity of sulfate-reducing bacteria (SRB) and particularly sulfur-oxidizing bacteria (SOB) communities from the shore sediments, favored the high-Eh and low-pH conditions adequate for the destabilization and transport of AuNp.

Marine particle microbiomes during a spring diatom bloom contain active sulfate-reducing bacteria.

Phytoplankton blooms fuel marine food webs with labile dissolved carbon and also lead to the formation of particulate organic matter composed of living and dead algal cells. These particles contribute to carbon sequestration and are sites of intense algal-bacterial interactions, providing diverse niches for microbes to thrive. We analyzed 16S and 18S ribosomal RNA gene amplicon sequences obtained from 51 time points and metaproteomes from 3 time points during a spring phytoplankton bloom in a shallow location (6-10 m depth) in the North Sea. Particulate fractions larger than 10 µm diameter were collected at near daily intervals between early March and late May in 2018. Network analysis identified two major modules representing bacteria co-occurring with diatoms and with dinoflagellates, respectively. The diatom network module included known sulfate-reducing Desulfobacterota as well as potentially sulfur-oxidizing Ectothiorhodospiraceae. Metaproteome analyses confirmed presence of key enzymes involved in dissimilatory sulfate reduction, a process known to occur in sinking particles at greater depths and in sediments. Our results indicate the presence of sufficiently anoxic niches in the particle fraction of an active phytoplankton bloom to sustain sulfate reduction, and an important role of benthic-pelagic coupling for microbiomes in shallow environments. Our findings may have implications for the understanding of algal-bacterial interactions and carbon export during blooms in shallow-water coastal areas.

Investigating organic sulfur in estuarine and offshore environments: A combined field and cultivation approach

Estuarine-offshore sediments accumulate substantial particulate organic matter, containing organic sulfur as a key component. However, the distribution and sources of organic sulfur in such environments remain poorly understood. This study investigated organic sulfur in the Yangtze River Estuary and adjacent East China Sea. Dissolved organic sulfur varied from 0.65 to 1.99 μmol/L (molar S:C 0.006–0.018), while particulate organic sulfur ranged from 0.42 to 2.69 μmol/L (molar S:C 0.007–0.082). Sedimentary organic sulfur exhibited a similar molar S:C ratio (0.014–0.071) to particulate organic sulfur in bottom water, implying that particulate matter deposition is a potential source. Furthermore, sediments exposed to frequent hypoxia harbored significantly higher organic sulfur and S:C values compared to non-hypoxic areas. Laboratory incubation experiments revealed the underlying mechanism: sustained activity of sulfate-reducing bacteria in hypoxic sediments led to a substantial increase in sedimentary organic sulfur (from 15 to 53 μmol/g) within 600 days. This microbially driven sulfurization rendered over 90 % of the organic sulfur resistant to acid hydrolysis. Therefore, this study demonstrates that, alongside particle deposition, microbial sulfurization significantly contributes to organic sulfur enrichment and likely promotes organic matter preservation in estuarine-offshore sediments, particularly under hypoxic conditions. This finding advances our understanding of organic sulfur sources in these vital ecosystems.

Review of bacterial sulfate reduction in lacustrine deposition and its identification in the Jimsar Sag, Junggar Basin

Bacterial sulfate reduction (BSR) is the interaction between sulfates and organic matter that bacteria participate in during the early diagenetic stage. It is one of the important biogeochemical processes that affect the formation of sulfides and sulfur cycling. Due to the lack of sulfate in the lakes, there is relatively little research on lacustrine bacterial sulfate reduction (LBSR), and related research mainly focuses on marine sedimentation. Marine incursion and volcanic ash may bring sulfate to lakes, providing a possibility for the occurrence of LBSR. The process, main influencing factors, and identification methods of BSR are summarized systematically. Through comprehensive analysis, it is believed that the occurrence depth of LBSR is relatively shallow (about 10 cm). Sulfate concentration, total organic matter, and sulfate reducing bacteria activity are the main controlling factors of BSR. The petrological and geochemical characteristics of the product are commonly used indicators to determine whether BSR occurs. The Jimsar Sag is one of the important shale oil rich areas in China. Taking Jimsar Sag as an example, the identification of LBSR was attempted. Based on the characteristics of framboidal pyrite, columnar calcite, and fine-grained dolomite, comprehensive analysis suggests that LBSR has occurred in the Lucaogou Formation of the Jimsar Sag. BSR has a significant effect on the degradation of organic matter, and TOC is usually lower in areas with higher intensity. Therefore, BSR has impact on the enrichment of organic matter in shale. The relevant research may have reference significance for the enrichment of lacustrine organic matter and shale oil exploration.

Гуанідінійвмісний олігомер як інгібітор мікробної корозії металу

Guanidinium-containing oligomers, a poorly studied class of organic compounds, have attracted attention due to their bactericidal properties. A guanidinium-containing oligomer based on an aliphatic oligoepoxide is a newly synthesized substance with bactericidal activity, which gives it the prospects for use as a microbial corrosion inhibitor. Aim. The goal of the study was to synthesize oligomeric alkyl substituted guanidinium bromide and study of its anticorrosive properties in the presence of steel under the influence of corrosive active sulfate-reducing bacteria. Methods. The guanidine-containing alkyl substituted oligomer was obtained by the reaction of the aliphatic oligoepoxide DEG-1 with guanidine, followed by interaction with alkyl bromide. The anticorrosive properties of the guanidine-containing oligomer were studied using collection strains of sulfate-reducing bacteria: UCM B-11503 Desulfovibrio sp.10, UCM B-11501 Desulfovibrio desulfuricans DSM642, and UCM B-11502 Desulfovibrio vulgaris DSM644. The sulfate-reducing bacteria were grown on Postgate В medium for 14 days at a temperature of 28 ± 2 °C. The number of bacteria was determined by the method of tenfold dilution. The corrosion rate was determined by the gravimetric method. The physicochemical parameters of pH and redox potential of the bacterial culture liquid were studied by the potentiometric method. The accumulation of hydrogen sulfide in the culture liquid was determined by the iodometric method. Lipolytic activity was studied spectrophotometrically using a KFK-3 device by reaction with p-nitrophenyl palmitate, catalase activity — using 0.03% hydrogen peroxide, which formed a stable colored complex with a 4% molybdenum diphosphate solution. The specific activity of the studied enzymes was expressed as unit ∙ mg-1 protein. Protein was determined in the supernatant by the conventional Lowry method. Results. It was shown that the oligomer based on aliphatic oligoepoxide has biocidal properties. A significant inhibition of the development of sulfate-reducing bacteria (SRB) was observed after the oligomer was added; only dozens of bacterial cells were detected in the medium after the exposure period. The corrosion rate of steel in the presence of SBR without addition of inhibitors was 0.15 — 0.35 mg/cm2∙h. The addition of DPC (a quaternary ammonium compound based on N-decylpyridinium chloride) (Kyiv Polytechnic Institute (KPI), Ukraine) to the culture medium led to a decrease in the steel corrosion rate to 0.032 — 0.047 mg ∙ cm-2  h-1 (by 6.5—10.6 times). In the presence of Armohib CI-28 inhibitor (based on Diamine Ethoxylate) (Akzonobel, Holland), the corrosion rate was reduced to 0.02—0.039 mg ∙ cm-2  h-1 (by 4.2 — 12.7 times). The addition of guanidinium-containing oligomer to the medium with bacteria reduced the corrosion rate to 0.075—0.079 mg/cm2 ∙ h (by 2.5—2.7 times). According to the mass loss of steel samples, the degree of metal protection against microbial corrosion in the presence of guanidinium-containing oligomer was 60.15—63.17%. Conclusions. The obtained data indicate that the guanidinium-containing oligomer based on aliphatic oligoepoxy has biocidal and anticorrosive properties and is promising for use as a means of combating microbially induced corrosion.

Enhanced Biogenic Sulfidation of Zero-Valent Iron in Columns: Implications for Promoting Dechlorination in Permeable Reactive Barriers.

Biogenic sulfidation of zero-valent iron (ZVI) using sulfate reducing bacteria (SRB) has shown enhanced dechlorination rates comparable to those produced by chemical sulfidation. However, controlling and sustaining biogenic sulfidation to enhance in situ dechlorination are poorly understood. Detailed interactions between SRB and ZVI were examined for 4 months in column experiments under enhanced biogenic sulfidation conditions. SRB proliferation and changes in ZVI surface properties were characterized along the flow paths. The results show that ZVI can stimulate SRB activity by removing excessive free sulfide (S2-), in addition to lowering reduction potential. ZVI also hinders downgradient movement of SRB via electrostatic repulsion, restricting SRB presence near the upgradient interface. Dissolved organic carbon (e.g., >2.2 mM) was essential for intense biogenic sulfidation in ZVI columns. The presence of SRB in the upgradient zone appeared to promote the formation of iron polysulfides. Biogenic FeSx deposition increased the S content on ZVI surfaces ∼3-fold, corresponding to 3-fold and 2-fold improvements in the trichloroethylene degradation rate and electron efficiency in batch tests. Elucidation of SRB and ZVI interactions enhances sustained sulfidation in ZVI permeable reactive barrier.

AMINOMETHOXY DERIVATIVES OF 1-BENZYLTHIOOCTANE AS A BIOCORROSION INHIBITOR

Based on benzylthioctane-2-ol, heterocyclic amines (piperidine, morpholine, hexamethyleneimine), and formaldehyde, new Mannich bases were synthesized. The reaction was carried out at a temperature of 45–500C for 3–4 h. in an equimolar ratio of starting compounds. The yield of target products was 70–74%. The physicochemical data of the synthesized compounds were determined. The composition and structure of the target products were confirmed by elemental analysis, IR and 1H NMR spectroscopy. Their influence on the vital activity of sulfate-reducing bacteria of the Desulfovibrio desulfiricans type at three con¬centrations (25, 50, 100 mg/l) was studied. The obtained compounds showed high bactericidal pro¬perties, since 1% solutions of these compounds in isopropyl alcohol at a concentration of 100 mg/l showed a 100% bactericidal effect. Given that the aminomethoxy derivatives of 1-benzylthiooctane affect bacteria at very low concentrations, they can be proposed as effective inhibitors of sulfate reducing bacteria (SRB).

Biotic-Abiotic Radial-Acicular Crystal Fan Fabrics with Rosickýite at the Angel Springs Tufa-Travertine Deposit in Southern British Columbia

Abstract The tufa-travertine deposit at Angel Springs developed through the interaction of thermal waters with bedrock of the Proterozoic Okanagan Gneiss, which extends along the eastern margin of the Okanagan Valley fault system in south-central British Columbia. This warm spring is proximal to Miocene plateau basalt flows that cut the Okanagan Gneiss bedrock eastward of the Okanagan Valley. The carbonate deposit, which is widely referenced as tufa, consists of a tufa and an overlying travertine. These texturally and petrographically different deposits developed in response to a shift in the groundwater pathway wherein the surface discharge transitioned from multiple vents of the tufa to a single downslope vent pool of the overlying travertine. Lower interval tufa fabrics are characterized by networks of fenestral-type porosity supported by a framework of curvilinear stromatolitic sheets of calcite that resulted from the partial coalescence of sub-horizontal arrays of calcite-encrusted cyanobacteria. These tufa fabrics aligned with the strong stream flow emanating from multiple vents. In contrast, radial crystal fan fabrics of the upper interval travertine developed with the transition from biotic calcite encrustations of upward branching cyanobacteria to the abiotic development of radial crystal fans. Length-long mouldic porosity tubules were occluded as the abiotic sheaf- and fan-shaped crystal growth surfaces expanded radially with rapid degassing. Core areas of the radial crystal arrays coalesced and were partially recrystallized, resulting in spheroidal crystalline fabrics that preserve inclusion-delineated concentric growth surfaces. Syntaxial overgrowths of radially aligned acicular crystals rapidly expanded from these core areas of coalesced calcite, resulting in the formation of abiotic radial-acicular and starburst crystal arrangements. The biotic–abiotic transition resulted in the rapid growth of abiotic crystal fans as the dominant deposition process of the upper interval travertine fabrics, but not in the lower interval tufa fabrics. Activities of sulfate-reducing bacteria in the sulfate-rich thermal water of both intervals resulted in precipitation of rosickýite, the monoclinic polymorph of S, as nanocrystalline globular protuberances on surfaces of calcite crystals. This is the first recorded occurrence of rosickýite in a tufa-travertine deposit and the first recognition of this mineral in Canada.

Effect of Photo Irradiation on the Anaerobic Digestion of Waste Sewage Sludge-Reduced Methane and Hydrogen Sulfide Productions

Since a large amount of sewage sludge (WSS) is generated daily, exploring effective methods for utilizing WSS is necessary. Although a photo-fermentation system sometimes alters the characteristics of microbial functions, there have been no attempts to perform photo-fermentation using WSS, which is regularly treated via dark fermentation. In this study, the effect of photo-fermentation (photo-irradiation) on anaerobic digestion using WSS was revealed. Photo-irradiation during the anaerobic digestion of WSS significantly reduced the amount of methane and hydrogen sulfide. Methane production was also reduced 5.6-fold at 13 days under light conditions, whereas hydrogen sulfide was consumed almost completely at 6 days. However, it was shown that the activity of sulfate-reducing bacteria in WSS under light treatment increased. Photo-irradiation also stimulated the growth of green sulfur bacteria and induced anoxygenic photosynthesis, via which process the fermented samples turned green in a manner that was correlated with their consumption of hydrogen sulfide. The production of organic acids was lowered in the samples that were irradiated using light. Finally, dark/light switching fermentation was only able to reduce hydrogen sulfide while methane production remained the same. The amounts of methane and hydrogen sulfide were 35 mmol/g VS, and they were undetected at 58 days in photo-irradiated samples compared to the control samples that produced 37 mmol/g VS of methane and 15 ppm/g VS of hydrogen sulfide.

Real-Time Electrochemical Monitoring of the Progress of Sulfate Reducing Bacterially Induced Corrosion of Carbon Steel

Microbiologically influenced corrosion (MIC) is a widespread problem in the oil and gas industry, and sulfate reducing bacteria (SRB) cause the most aggressive kind of corrosion. A sulfate-reducing enrichment culture was obtained from a natural gas transmission line, and incubated in split chamber-zero resistance ammetry incubations. Here, carbon steel electrodes were placed in a synthetic gas field brine in opposing chambers that were connected with a salt bridge. To mimic the heterogeneous metal coverage of a metal surface that causes MIC, one chamber was experimentally manipulated with the addition of the SRB culture, while the other was uninoculated. Initial measurement of positive current between the electrodes in incubations with an organic electron donor (lactate) indicated a period of priming of the metal surface by planktonic SRB, before the current transitioned to negative, indicating that the cathodic corrosive reaction was occurring on the electrode exposed to SRB activities. This negative current is consistent with hypothesized mechanisms of SRB-induced corrosion and was observed in lactate-free incubations and in uninoculated incubations amended with sulfide. These observations, combined with SRB metabolic patterns and mass loss analyses indicate the dynamic nature of SRB-mediated corrosion and illustrate the utility of real-time monitoring of MIC activities.

Spatiotemporal Changes in Trace Metal Bioavailability in the Sediment Pore water of a Constructed Wetland Using Passive Pore water Samplers.

Sediments in aquatic systems often act as a major sink for contaminants. Diffusive gradient in thin films (DGTs) and in situ equilibrium dialysis samplers (peepers) are two major in situ pore water sampling devices that overcome the problems associated with conventional pore water sampling methods. In the present study, DGTs and peepers were used to study the spatial and seasonal effects (cool months, October-February; warm months, May-September) on metal bioavailability in the H-02 constructed wetland and the sink versus source role of the sediments by calculating the metal resupply capacity. Data showed similar seasonal trends in metal concentrations using passive samplers, peepers, and DGTs. Pooled Cu and Zn concentrations measured using DGTs were lower in warm months (1.67 ± 1.50 and 2.62 ± 0.68 μg L-1 , respectively, p < 0.001) versus in cool months (2.12 ± 0.65 and 5.58 ± 1.33 μg L-1 , respectively, p < 0.001; mean ± 95% confidence interval). Sulfate (SO4 2- ) concentrations were significantly (p = 0.0139) lower in warm months (averaged at 0.22 ± 0.05 mg L-1 ) compared to in cool months (0.16 ± 0.05 mg L-1 ). The increase in SO4 2- concentration is an indicator of the lower activity of sulfate-reducing bacteria, which need SO4 2- during anaerobic respiration, in which SO4 2- is reduced to sulfide (S2- ) that forms insoluble salts with Cu and Zn, which could partially explain the higher bioavailability of these metals in the cool season. Metal resupply capacity of the sediments was mostly <0.2 for Cu and Zn. Taken together, the H0-2 wetland sediments mostly acted as a sink to both Cu and Zn over the course of the present study. Environ Toxicol Chem 2023;42:2726-2736. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Synergistic passivation performance of cadmium pollution by biochar combined with sulfate reducing bacteria

The use of sulfate-reducing bacteria (SRB) for the remediation of Cd-contaminated soil is an attractive option. However, there are various factors that limit the activity of free SRB in soil, which hinders the rapid reduction of sulfate. The immobilized SRB technology has been proposed as a possible solution to overcome this barrier. This study aimed to isolate an Enterobacter sp. strain (SRB15-3-2) with high resistance to Cd2+ from a tailing. Wheat, maize, and rice straws were selected to prepare biochar for inoculating the screened bacteria. The results showed that wheat straw biochar pyrolyzed at 700 °C (WS700) had the highest performance in carrying SRB for Cd2+ immobilization. Furthermore, the WS700 was found to promote SRB15-3-2 for offering S2− and functional groups (C-S, C=O, C=C, C-C=O, and C-O-C, etc.) during the immobilization process. The immobilized SRB with WS700 (ISRBWS700) agglomerated and reacted with Cd2+ to form metal precipitations, predominantly CdS and CdCO3. Which lead to a significant decrease of exchangeable-Cd in contaminated soil (with initial Cd concentrations of 1, 5, and 20 mg/kg) by 18.5%–31.6% after applying the ISRBWS700, indicating that the indigenous soil microbes were been protected from Cd toxicity. Additionally, ISRBWS700 exhibited a synergistic effect in enhancing SRB15-3-2 propagation and the activities of saccharase, urease, and acid phosphatase, compared to the separate treatment of SRB15-3-2 and WS700. Overall, ISRBWS700 prepared in this study represented an accessible way to resolve Cd-contaminated soil, which provided new theoretical insights into eco-friendly technologies for Cd-polluted soil remediation both in development and sustainable aspects.

DEVELOPMENT AND APPLICATION OF NEW COMPOSITIONS TO IMPROVE THE EFFICIENCY OF OIL FIELD EQUIPMENT OPERATION

One of the urgent problems in the oil industry is the reliable protection of oil field equipment from corrosion. With this in mind, as a result of laboratory studies, three compositions were developed based on phospholipids, fatty acids, phosphoric acid, nitrogen compounds, asidol, naphthenic acids and light gas oil. The complexity of the composition gives the resulting compositions multifunctionality and allows them to be used in various aggressive conditions.&#x0D; In laboratory conditions, the effect of these compositions on the corrosion rate of metals and on the vital activity of sulfate reducing bacteria (SVB) was studied. Based on the obtained results, the concentration of the compositions (500 mg/l) was established, providing a protective effect against corrosion, which was 94–95 %, and the degree of suppression of SVB was 97–99 %.&#x0D; Field tests of corrosion inhibitors also yielded positive results: the protective effect against corrosion was 89–90 %, and the degree of SVB suppression was 92–97 %.

Hydrogen-induced cracking of X70 steel affected by sulfate-reducing bacteria and cathodic potential: experiment and density functional theory study

Submarine pipeline are often exposed to the risk of hydrogen embrittlement from the dual action of marine sulfate-reducing bacteria (SRB) and cathodic protection (CP). In this work, hydrogen permeation test, slow strain rate tensile (SSRT) experiments, and density functional theory (DFT) were used to explain the hydrogen embrittlement (HE) mechanism of subsea pipeline steel under the action of SRB and CP. When the applied CP potential is increased from −850 mV to −1200 mV, the hydrogen seepage current increases 1.8 times. And the tensile specimens pre-charged with hydrogen exhibit significant hydrogen embrittlement behavior. DFT calculations show that the increased concentration of hydrogen atoms on the material surface decreases the diffusion potential barrier, leading to a larger hydrogen seepage current. In addition, the aggregation of hydrogen atoms in the steel weakens the chemical bonds between Fe atoms, leading to hydrogen embrittlement.

Corrosion inhibition study of marine Streptomyces against sulfate-reducing bacteria in oilfield produced water

A marine Streptomyces sp., which has an inhibitory effect on sulfate-reducing bacteria (SRB), was selected to study inhibitory effect and mechanism of X65 steel on SRB corrosion in oilfield produced water. Streptomyces and SRB had a competitive growth relationship. The Streptomyces metabolites affected the number and activity of SRB and had good corrosion inhibiting properties. The formation and development of SRB biofilm was inhibited. Mixed bacteria inhibited anodic dissolution of X65 steel and slowed down the electrochemical reaction rate. The film layer on the sample was denser, and the average and localized corrosion rates caused by SRB were significantly suppressed.

Arsenic (III) and arsenic (V) removal from acidic mine waters using an acidophilic sulfate-reducing bioreactor

Chile accounts for about one-third of the world's copper production; however, high levels of arsenic (As) in its copper concentrates have generated problems and subsequent challenges for the mining industry. In particular, the requirement of additional processing for arsenic removal from aqueous solutions from mining operations. In this technology area, cost effective biotechnological approaches for remediating this metalloid, using acidophilic sulfate reducing bacteria (SRB) can be an attractive alternative to current systems for As removal from acidic mine water. Here we describe the performance of two acidophilic continuous fed bioreactors for the removal of arsenic (III) and arsenic (V). The biofilm-based continuous bioreactors were inoculated with a mixed culture including an acidophilic sulfate reducer (Desulfosporosinus acididurans). Both bioreactors were fed with an acidic synthetic water (pH 2.1) for up to 420 days, with varying concentrations of As3+ and As5+ (2–150 ppm) and using glycerol as carbon and energy source. The results demonstrated that over 95% of both forms of As were removed as arsenic sulfide. The hydraulic retention times (HRT) increased up to 350 h for higher concentrations of As. Considering that the pH of the bioreactor liquor was maintained at pH 4.5 by the addition of the synthetic mine water, the increased HRT was correlated with a decrease in SRB activity. This study demonstrated the feasibility of removing As (III) and As (V) from an extremely acidic water by using a continuous acidophilic SRB bioreactor, expanding the use of this technology for the remediation of this metalloid.

Microbial characteristics and potential mechanisms of souring control for a hypersaline oil reservoir

The production of hydrogen sulfide (H2S) had caused huge economic losses and security risks to oil fields, which had attracted the attention of many researchers. Studies focused on hypersaline oil reservoirs were scarce. Here, we simulated H2S inhibition by adding NO3 - and NO2 - in anaerobic bottles and up-flow sand-packed bioreactor in the laboratory using water samples from injection wells in the Jianghan reservoir. The microbial characteristics, pH, salinity, sulfate, sulfide, NO3 - and NO2 - were measured at every stage. The content of H2S and elemental sulfur (S0) gradually reduced to 0 mg/L with injected 400 mg/L of NO3 - and 300 mg/L of NO2 -. Halophilic nitrate-reducing bacteria (NRBs) related to Halomonas and Arcobacter could suppress the activity of sulfate-reducing bacteria (SRBs) through the accumulation of nitrite toxicity and the competition of organic substrates with SRBs. When SRBs activity could not be suppressed, the sulfur-oxidizing bacteria related to Sulfurimonas, Thiomicrospira and Acrobacter were accumulated for souring control through microbial sulfur cycle of H2S production and oxidation. Salinity could be a key parameter affecting microbial development and interactions. This study provides a fundamental data to souring control in the hypersaline oil reservoir by reinjection produced water amended with NO3 - and NO2 -.

Antibacterial Effect of Low-Concentration ZnO Nanoparticles on Sulfate-Reducing Bacteria under Visible Light.

The effect of ZnO nanoparticles (ZnO NPs), with different concentrations in simulated water, on the activity of sulfate-reducing bacteria (SRB) and their adhesion behaviour on stainless-steel surfaces, with and without visible light treatment, were investigated. The results showed that the concentration of ZnO NPs and light treatment greatly influenced the antibacterial performance of the NPs. In the water solution without light treatment, the low concentration (no more than 1 mg/L) of ZnO NPs in the aqueous solution promoted the growth of SRB, and the amount of biofilm attached to the stainless-steel surface increased. As the concentration increased, ZnO NPs exhibited antibacterial effects. In water under visible light irradiation, ZnO NPs showed antibacterial performance at all the concentrations studied (0.5~50 mg/L), and the antibacterial efficiency increased with the increase in the concentration of NPs. The determination results of the reactive oxygen species showed that light treatment can stimulate ZnO NPs in water to generate ·OH and O2·-, which exhibited good antibacterial properties. The adhesion amount of SRB on the stainless-steel surface was inversely proportional to the antibacterial efficiency of ZnO NPs.