Anaerobic Sulfate-reducing Bacteria Research Articles

The different effects of molybdate on Hg(II) bio-methylation in aerobic and anaerobic bacteria

In nature, methylmercury (MeHg) is primarily generated through microbial metabolism, and the ability of bacteria to methylate Hg(II) depends on both bacterial properties and environmental factors. It is widely known that, as a metabolic analog, molybdate can inhibit the sulfate reduction process and affect the growth and methylation of sulfate-reducing bacteria (SRB). However, after it enters the cell, molybdate can be involved in various intracellular metabolic pathways as a molybdenum cofactor; whether fluctuations in its concentration affect the growth and methylation of aerobic mercury methylating strains remains unknown. To address this gap, aerobic γ-Proteobacteria strains Raoultella terrigena TGRB3 (B3) and Pseudomonas putida TGRB4 (B4), as well as an obligate anaerobic δ-Proteobacteria strain of the SRB Desulfomicrobium escambiense CGMCC 1.3481 (DE), were used as experimental strains. The growth and methylation ability of each strain were analyzed under conditions of 500 ng·L−1 Hg(II), 0 and 21% of oxygen, and 0, 0.25, 0.50, and 1 mM of MoO42−. In addition, in order to explore the metabolic specificity of aerobic strains, transcriptomic data of the facultative mercury-methylated strain B3 were further analyzed in an aerobic mercuric environment. The results indicated that: (a) molybdate significantly inhibited the growth of DE, while B3 and B4 exhibited normal growth. (b) Under anaerobic conditions, in DE, the MeHg content decreased significantly with increasing molybdate concentration, while in B3, MeHg production was unaffected. Furthermore, under aerobic conditions, the MeHg productions of B3 and B4 were not influenced by the molybdate concentration. (c) The transcriptomic analysis showed several genes that were annotated as members of the molybdenum oxidoreductase family of B3 and that exhibited significant differential expression. These findings suggest that the differential expression of molybdenum-binding proteins might be related to their involvement in energy metabolism pathways that utilize nitrate and dimethyl sulfoxide as electron acceptors. Aerobic bacteria, such as B3 and B4, might possess distinct Hg(II) biotransformation pathways from anaerobic SRB, rendering their growth and biomethylation abilities unaffected by molybdate.

Nitrogen and sulfur for phosphorus: Lipidome adaptation of anaerobic sulfate-reducing bacteria in phosphorus-deprived conditions

Understanding how microbial lipidomes adapt to environmental and nutrient stress is crucial for comprehending microbial survival and functionality. Certain anaerobic bacteria can synthesize glycerolipids with ether/ester bonds, yet the complexities of their lipidome remodeling under varying physicochemical and nutritional conditions remain largely unexplored. In this study, we thoroughly examined the lipidome adaptations of Desulfatibacillum alkenivorans strain PF2803T, a mesophilic anaerobic sulfate-reducing bacterium known for its high proportions of alkylglycerol ether lipids in its membrane, under various cultivation conditions including temperature, pH, salinity, and ammonium and phosphorous concentrations. Employing an extensive analytical and computational lipidomic methodology, we identified an assemblage of nearly 400 distinct lipids, including a range of glycerol ether/ester lipids with various polar head groups. Information theory-based analysis revealed that temperature fluctuations and phosphate scarcity profoundly influenced the lipidome's composition, leading to an enhanced diversity and specificity of novel lipids. Notably, phosphorous limitation led to the biosynthesis of novel glucuronosylglycerols and sulfur-containing aminolipids, termed butyramide cysteine glycerols, featuring various ether/ester bonds. This suggests a novel adaptive strategy for anaerobic heterotrophs to thrive under phosphorus-depleted conditions, characterized by a diverse array of nitrogen- and sulfur-containing polar head groups, moving beyond a reliance on conventional nonphospholipid types.

Effect of Sulphate-Reducing Bacteria Activity on the Performance of Thermally Sprayed Aluminium and Polyurethane Coatings

In the present work, we studied whether the exposure of synthetic seawater with anaerobic sulphate-reducing bacteria (SRB) on some steel samples generates a bacterial biofilm in their surfaces. Bare steel belonging to a mooring chain as well as two coating systems applied on the steel surface were studied: polyurethane (PU) and thermally sprayed aluminium (TSA) with and without an epoxy-based sealant. After 30 days of immersion in SRB-inoculated synthetic seawater, a bacterial count was attained, and the samples were observed using scanning electron microscopy (SEM) and locally analysed using X-ray scattered energy spectroscopy (EDS). A biofilm developed on every tested surface (continuous or in the form of pustules), with evidence of metabolic activity of the SRB. Finally, a mechanism of degradation for TSA in the presence of SRB is proposed for environments with a high concentration of bacteria.

Corrosion mechanism and research progress of metal pipeline corrosion under magnetic field and SRB conditions: a review

Abstract Biocides are used to prevent microbiologically influenced corrosion (MIC), which damages and disables metal structures. However, biocides can make microorganisms resistant and contaminate the environment. Some studies have found that magnetic fields have an inhibitory effect on MIC, providing a new way of thinking for MIC control. In this paper, the current research status of MIC is discussed for typical anaerobic sulfate-reducing bacteria (SRB), the MIC of different metals in different environments is summarized, and the corrosion mechanism of SRB on metal structures, including cathodic depolarization and metabolite corrosion, is introduced. On this basis, the research progress of metal corrosion under magnetic field and microbial conditions in recent years is summarized, and discussed from three aspects, namely, electrochemical corrosion, SCC, and microbial corrosion, respectively. The corrosion process of microorganisms on metals in magnetic field is summarized, including biofilm theory, ion interference theory, free radical theory, and so on. Finally, the prevention and control of microbial corrosion by magnetic fields are prospected using the relevant mechanisms of magnetic field corrosion on metals.

Highly efficient oxygen evolution catalysts prepared by bacteria Desulfovibrio caledoniensis and Pseudomonas stutzeri based on Ni-Fe foam

Oxygen evolution reaction (OER) has gained increasing attention among researchers due to its significance in energy conversion. However, the sluggish kinetics of the OER present notable challenges. In this work, we present an energy-efficient, cost-effective, widely applicable, and scaled-up biological preparation method to prepare OER catalytic materials with high activity and stability based on bacteria and inexpensive Ni-Fe foam under mild conditions. Anaerobic sulfate-reducing bacterium Desulfovibrio caledoniensis and aerobic Pseudomonas stutzeri are the typical microorganisms and the OER performance of their products is not clear. Electrochemical measurements show that the catalyst prepared via D. caledoniensis exhibits a low overpotential of only 247 mV to achieve 10 mA cm−2 and a low Tafel slope of 46 mV dec-1, while the catalyst prepared via P. stutzeri has an overpotential and Tafel slope of 259 mV and 71 mV dec-1, respectively. Therefore, these catalysts exhibit excellent catalytic activities. Furthermore, they have a good stability of more than 40 h at 10 mA cm−2 which is far superior to that of the majority of reported NiFe-based OER catalysts. This work shows new insights into the preparation and development of high-performance OER catalysts in mild conditions.

The Isolation of Anaerobic and Facultative Anaerobic Sulfate-Reducing Bacteria (SRB) and a Comparison of Related Enzymes in Their Sulfate Reduction Pathways.

Sulfate-reducing bacteria (SRB) are an important group of microorganisms that cause microbial corrosion. In this study, culturable SRB were isolated and identified from the inner rust layer of three kinds of steel and from sediments, and a comparison of amino acid sequences encoding related enzymes in the sulfate reduction pathway between anaerobic and facultative anaerobic SRB strains was carried out. The main results are as follows. (1) Seventy-seven strains were isolated, belonging to five genera and seven species, with the majority being Desulfovibrio marinisediminis. For the first time, Holodesulfovibrio spirochaetisodalis and Acinetobacter bereziniae were separated from the inner rust layer of metal, and sulfate reduction by A. bereziniae, Virgibacillus dokdonensis, and Virgibacillus chiguensis, etc., was also demonstrated for the first time. (2) Three strains of strictly anaerobic bacteria and four strains of facultative anaerobic bacteria were screened from seven bacterial strains. (3) Most of the anaerobic SRB only contained enzymes for the dissimilatory sulfate reduction pathway, while those of facultative anaerobic bacteria capable of producing hydrogen sulfide included two possible ways: containing the related enzymes from the dissimilatory pathway only, or containing enzymes from both dissimilatory and assimilation pathways. This study newly discovered that some bacterial genera exhibit sulfate reduction ability and found that there are differences in the distribution of enzymes related to the sulfate reduction pathway between anaerobic and facultative anaerobic SRB type trains, providing a basis for the development and utilization of sulfate-reducing bacterial resources and furthering our understanding of the metabolic mechanisms of SRB.

A novel strictly anaerobic sulfate-reducing diazotrophic bacterium Fundidesulfovibrio terrae sp. nov., isolated from paddy soil.

A strictly anaerobic sulfate-reducing strain, designated SG127T, was isolated from paddy soil. SG127T showed the highest 16S rRNA gene sequence similarity to the type strain of Fundidesulfovibrio magnetotacticus (98.2 %). A phylogenetic tree based on 16S rRNA gene sequences indicated that SG127T clustered with members of the genus Fundidesulfovibrio. Growth of SG127T was observed at 20-37 °C (optimum, 30 °C), pH 5.5-9.0 (optimum, 7.0-8.0) and with 0-0.2 % (w/v) NaCl (optimally without NaCl). SG127T contained MK-7 as the only menaquinone and anteiso-C15 : 0, anteiso-C17 : 1ω9c, C18 : 0, iso-C14 : 0, iso-C15 : 0, iso-C16:0, iso-C16 : 1H, iso-C18 : 1H and summed feature nine as the major fatty acids. The genomic DNA G+C content of SG127T was 64.6 %. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between SG127T and the closely related Fundidesulfovibrio magnetotacticus were 78.5% and 23.2 %, respectively, which were lower than the cut-off values (ANI 95-96% and dDDH 70 %) for prokaryotic species delineation. SG127T had desulfoviridin, possessed nitrogen fixation genes (nifHDK) and actively fixed nitrogen according to the acetylene reduction assay. On the basis of these results, strain SG127T represents a novel species of the genus Fundidesulfovibrio, for which the name Fundidesulfovibrio terrae sp. nov. is proposed. The type strain is SG127T (= GDMCC 1.3137T = JCM 35589T).

Novel blade-like structure of reduced graphene oxide/α-Mn2O3 nanocomposite as an antimicrobial active agent against aerobic and anaerobic bacteria

For the first time, we developed a novel nanocomposite of RGO decorated with α-Mn2O3 nanorods (NRs) for inhibiting microbially influenced corrosion. RGO sheets with 2 nm thick were effectively synthesized by the modified Hummers technique and then a hydrothermal reduction procedure. The fabricated RGO/α-Mn2O3 nanocomposite exhibited controlled morphology, geometry, surface exposure, and orientation. Single crystal α-Mn2O3 NRs with mean diameter of 50 nm and length of 1 μm were produced via the hydrothermal procedure to yield γ-manganite which was calcined at 700 °C. Stable RGO/α-Mn2O3 nanocomposite was successfully prepared via an efficient two-phase ultrasonication approach. The structures of the developed materials and nanocomposite were detected via different characterization techniques. Cost-effectiveness, long-term antimicrobial activity, and biocorrosion inhibition are the major advantages of the produced RGO/α-Mn2O3 nanocomposite. The nanocomposite's biocorrosion-protection was influenced by its high surface area and controlled size and morphology. Its antimicrobial mechanism against different anaerobic and aerobic microbial strains was deeply highlighted. Field emission SEM images showed that the blade-like RGO/α-Mn2O3 nanocomposite cruelly attached into the microbial cell walls forming morphology disruption, cell wrapping, and microbial killing. This nanocomposite exhibited ultrahigh potency against the anaerobic sulfate-reducing bacteria (SRB) strain Desulfovibrio halophilus SL 890 at 150 mg/L. Its highest potency against most of the tested aerobic strains was achieved at 2 μg/mL for Kocuria rhizophila EMCC 1246, Bacillus subtilis EMCCN 1152, Pseudomonas aeruginosa NRRL B-800, Staphylococcus aureus ATCC 25923, Aspergillus brasiliensis ATCC 9642, and Candida albicans ATCC 24433. The designed RGO/α-Mn2O3 nanocomposite provide a new platform for microbial growth inhibition.

NMR-based metabolomic analysis of the physiological role of the electron-bifurcating FeFe-hydrogenase Hnd in Solidesulfovibrio fructosivorans under pyruvate fermentation

Solidesulfovibrio fructosivorans (formely Desulfovibrio fructosovorans), an anaerobic sulfate-reducing bacterium, possesses six gene clusters encoding six hydrogenases catalyzing the reversible oxidation of hydrogen gas (H2) into protons and electrons. One of these, named Hnd, was demonstrated to be an electron-bifurcating hydrogenase Hnd (Kpebe et al., 2018). It couples the exergonic reduction of NAD+ to the endergonic reduction of a ferredoxin with electrons derived from H2 and whose function has been recently shown to be involved in ethanol production under pyruvate fermentation (Payne 2022). To understand further the physiological role of Hnd in S. fructosivorans, we compared the mutant deleted of part of the hnd gene with the wild-type strain grown on pyruvate without sulfate using NMR-based metabolomics. Our results confirm that Hnd is profoundly involved in ethanol metabolism, but also indirectly intervenes in global carbon metabolism and additional metabolic processes such as the biosynthesis of branched-chain amino acids. We also highlight the metabolic reprogramming induced by the deletion of hndD that leads to the upregulation of several NADP-dependent pathways.

A Novel Coenzyme A Analogue in the Anaerobic, Sulfate-Reducing, Marine Bacterium Desulfobacula toluolica Tol2T.

Coenzyme A (CoA) thioesters are formed during anabolic and catabolic reactions in every organism. Degradation pathways of growth-supporting substrates in bacteria can be predicted by differential proteogenomic studies. Direct detection of proposed metabolites such as CoA thioesters by high-performance liquid chromatography coupled with high-resolution mass spectrometry can confirm the reaction sequence and demonstrate the activity of these degradation pathways. In the metabolomes of the anaerobic sulfate-reducing bacterium Desulfobacula toluolica Tol2T grown with different substrates various CoA thioesters, derived from amino acid, fatty acid or alcohol metabolism, have been detected. Additionally, the cell extracts of this bacterium revealed a number of CoA analogues with molecular masses increased by 1 dalton. By comparing the chromatographic and mass spectrometric properties of synthetic reference standards with those of compounds detected in cell extracts of D. toluolica Tol2T and by performing co-injection experiments, these analogues were identified as inosino-CoAs. These CoA thioesters contain inosine instead of adenosine as the nucleoside. To the best of our knowledge, this finding represents the first detection of naturally occurring inosino-CoA analogues.

Steel rust layers immersed in the South China Sea with a highly corrosive Desulfovibrio strain

Although it is well known that microbes play a significant role in marine corrosion, few studies have systematically studied the relationship between microorganisms and corrosion products under long-term immersion. In this study, the corrosion characteristics of the rust layer formed on carbon steel immersed in the South China Sea for 5.5 years were investigated using various surface analysis and microbial community analysis techniques. Magnetite (Fe3O4), iron sulfide, and green rust were identified in the inner rust layer. The middle rust layer was composed of maghemite (γ-Fe2O3), and some Fe3O4 and mackinamite were also detected. The outer rust layer contained several Fe(III)-oxyhydroxides, and it had a large number of fouling organisms attached to it. In all of the rust layers, anaerobic sulfate-reducing bacteria (SRB) were the dominant bacteria, and they may have played a key role in the formation of the corrosion products. One SRB strain (Desulfovibrio bizertensis SY-1) with a highly corrosivity (13.561 mg/cm2) was isolated from these rust layers, and its physiological and metabolic characteristics were studied. These results expand the membership of corrosive SRB and establish a better understanding of marine microbiologically influenced corrosion (MIC).

Assessing Alternative Supporting Organic Materials for the Enhancement of Water Reuse in Subsurface Constructed Wetlands Receiving Acid Mine Drainage

Acid mine drainage (AMD) is a global problem with severe consequences for the environment. South Africa’s abandoned mines are a legacy from the country’s economic dependence on the mining sector, with consequent negative impacts on ecosystems. AMD remediation includes active and passive techniques. Constructed wetlands (a passive technique) have lower operational costs but require larger spaces and longer timeframes to achieve the remediation of AMD, and are supported by anaerobic sulphate-reducing bacteria (SRB), which capable of remediating high-sulphate-laden AMD while precipitating dissolved metals from the AMD. Organic substrates supporting these activities are often the limiting factor. When enhancing existing passive AMD remediation technologies, alternative waste material research that may support SRB activity is required to support the circular economy through the reduction in waste products. Chicken feathers show potential as a substrate enhancer, boosting organic carbon availability to SRB, which sustains passive AMD treatment processes by achieving pH elevation, sulphate and metal reductions in AMD water for reuse. Microbial biodiversity is essential to ensure the longevity of passive treatment systems, and chicken feathers are proven to have an association with SRB microbial taxa. However, the longer-term associations between the AMD water parameters, microbial diversity and the selected substrates remain to be further investigated.

Mineralogical and geochemical research on Pengyang deposit: A peculiar eolian sandstone-hosted uranium deposit in the southwest of Ordos Basin

The newly discovered Pengyang uranium prospect area in the southwest of the Ordos Basin is the world's first uranium deposit hosted in eolian sandstone, which overturned the conventional view of uranium mineralization in fluvial-delta sedimentary strata. Uranium ore body occurring as tabular or lens-shaped is hosted in the gray-green reductive eolian sandstone of Lower Cretaceous Luohe Formation at depths ranging from 700 m to 3000 m. The host eolian sandstone is characterized by the typical high angle cross-bedding, wind sand ripple and grainflow strata. In this study, we conducted borehole log, petrographic observation, whole rock geochemistry analysis, geochemical and mineralogical study of uranium occurrence (SEM), element mapping of uranium minerals and in-situ sulfur isotope determination of pyrite by LA-MC-ICP-MS to reveal the uranium enrichment mechanism. The observations by SEM show that the predominant uranium mineral is pitchblende, primarily occurring as aggregates of nano to micro crystals absorbed on amorphous TiO2 or as colloform replacing the detritus Fe-Ti oxide minerals, both demonstrating the excellent absorption property of small particles of anatase. The contents of altered minerals such as chlorite and pyrite in gray-green sandstone increased significantly under scanning electron microscope (SEM). Whole rock geochemistry analysis data of sandstone samples collected in the target layers display the strong positive correlation between U and S. Whereas, in the elements mapping images, uranium enrichments display complete dissociation with pyrite as the uranium contents adjacent to or around the pyrite grains are under detection limit, demonstrating that uranium precipitation likely occurred earlier than the sulfuration of red eolian sandstone. Sulfur isotope of the two morphological types of pyrite are both characterized by a relatively light signature, ranging from − 19.23 to − 27.22 ‰ and from − 21.60 to − 29.64‰ respectively, implying that they are generated from bacterial sulfate reduction in the open systems with an adequate supply of sulfate. Anaerobic sulfate-reducing bacteria use the hydrocarbon transferred along faults to the sandstone as energy to reduce sulfate (SO42−) to H2S. In addition to the typical vertical red - yellow - gray color zonation, we also observed distinct reverse color zonation of sandstone, which can hardly be interpreted by traditional interlayer-oxidation-zone theory. We attribute the uranium reduction to the encounter of downward penetrating oxygenated groundwater with the upward migrating oil and gas conducted by thrust faults, which are widespread distributed in the west margin of the Ordos Basin. This study gives a new insight into uranium metallogenic mechanism in eolian sandstone and underpins an effective vector for the exploration of sandstone-type uranium deposits in the western of the Ordos Basin.

Distinct methane-dependent biogeochemical states in Arctic seafloor gas hydrate mounds

Archaea mediating anaerobic methane oxidation are key in preventing methane produced in marine sediments from reaching the hydrosphere; however, a complete understanding of how microbial communities in natural settings respond to changes in the flux of methane remains largely uncharacterized. We investigate microbial communities in gas hydrate-bearing seafloor mounds at Storfjordrenna, offshore Svalbard in the high Arctic, where we identify distinct methane concentration profiles that include steady-state, recently-increasing subsurface diffusive flux, and active gas seepage. Populations of anaerobic methanotrophs and sulfate-reducing bacteria were highest at the seep site, while decreased community diversity was associated with a recent increase in methane influx. Despite high methane fluxes and methanotroph doubling times estimated at 5–9 months, microbial community responses were largely synchronous with the advancement of methane into shallower sediment horizons. Together, these provide a framework for interpreting subseafloor microbial responses to methane escape in a warming Arctic Ocean.

Investigation of mixed species biofilm on corrosion of X65 steel in seawater environment

Microbiologically influenced corrosion (MIC) is a complex process involving the cooperative effect of different bacterial species that coexist in the biofilm. Early studies focused on the MIC of single bacterial communities. However, in natural and industrial fields, biofilms are mostly composed of a variety of species. In this work, the effect of interspecific interaction on corrosion of X65 steel was investigated through the mixed culture of sulfate reducing bacteria (SRB) and iron oxidizing bacteria (IOB). Results demonstrated that the mixed microbial consortia created a cooperative effect to aggravate the local corrosion of X65 steel. Compared with the single species, the presence of IOB increased the growth activity of SRB cells and promoted the role of SRB in steel corrosion. The corrosion form on the surface of X65 steel gradually changed to annular pits induced by anaerobic SRB. The succession of dominant bacteria and the development of mixed species biofilm led to an increase in corrosion rate and local corrosion. The corrosion mechanism of X65 steel by mixed species biofilm at different stages was carefully elucidated.

Influencing mechanisms of siderite and magnetite, on naphthalene biodegradation: Insights from degradability and mineral surface structure

Biodegradation is the most economical and efficient process for remediating polycyclic aromatic hydrocarbons (PAHs) such as naphthalene (Nap). Soil composition is pivotal in controlling PAH migration and transformation. Iron minerals such as siderite and magnetite are the primary components of soil and sediment and play key roles in organic pollutant biodegradation. However, it is unclear whether siderite and magnetite promote or inhibit Nap biodegradation. The effects of siderite and magnetite on Nap biodegradation were investigated through batch experiments in this study. The results indicated that siderite increased Nap biodegradation efficiency by 7.87%, whereas magnetite inhibited Nap biodegradation efficiency by 3.54%. In the presence of siderite, Nap-degrading bacteria with acid-producing effects promoted siderite dissolution via metabolic activity, resulting in an increased Fe (II) concentration in solution which accelerated the iron reduction process and promoted Nap biodegradation. In addition, the presence of iron minerals altered the genus-level community structure. Anaerobic sulfate-reducing bacteria such as Desulfosporosinus occurred in the presence of siderite, indicating that sulfate reduction occurred in advance under the influence of siderite. In the presence of magnetite, Fe (III) in iron minerals were converted to Fe (II), and under the mediation of microorganisms, Fe (II) combined with carbonate to form secondary minerals (e.g., siderite). Secondary minerals were attached to the surface of magnetite, which inhibited magnetite dissolution and reduced the efficiency of Fe (III) utilization by microorganisms. Furthermore, as the reaction proceeds, acid-producing microorganisms promoted magnetite further dissolution, resulting in a longer duration of the Fe (III) reduction process. Bacteria utilizing sulfuric acid as the terminal electron acceptor consumed organic matter more rapidly than those using iron as the terminal electron acceptor. Therefore, magnetite inhibited Nap degradation. These observations enhance our understanding of the interaction mechanisms of iron minerals, organic pollutants, and degrading bacteria during the biodegradation process.

Modeling the anaerobic digestion of wastewater sludge under sulfate-rich conditions.

Anaerobic digestion (AD) is a biological treatment process to stabilize organic solids and produce biogas. If present, sulfate is reduced to sulfide by anaerobic sulfate-reducing bacteria and the sulfide can be toxic to anaerobic microorganisms. Here, the effect of high initial sulfate concentration on AD of wastewater sludge was investigated using lab-scale batch experiments. Additionally, a systematic mathematical modeling approach was applied for insight into the experimental results. Cumulative biogas and methane production decreased with increasing initial sulfate doses (0-3.300mgSL-1 ). The correlation between the sulfate dose and methane production was consistent with theoretical predictions and model results, indicating no toxic effect of sulfide on methane production. The carbon dioxide content in the biogas decreased linearly with the increasing sulfate dose, which is consistent with the model-predicted behavior of the bicarbonate and hydrogen sulfide buffering system. The examined high sulfate concentrations resulted in no clear negative effects on the COD removal or VSS destruction of the wastewater sludge, indicating negligible inhibition by sulfide toxicity. Even considering the possibility of ferrous sulfide precipitation and the low model estimates of residual sulfide concentration the residual sulfide concentration was higher than reported concentrations that trigger process inhibition. PRACTITIONER POINTS: The effect of sulfate loading on anaerobic digestion of waste activated sludge was characterized. The stoichiometry of sulfate reduction allows accurate prediction of CH4 loss. High sulfate levels (up to 3300mg/L as S) did not affect COD/VSS removal. Sulfide formation increases effluent COD; often misinterpreted as sulfide toxicity. Correcting COD for sulfide's contributions is crucial for results interpretation.

Preparation of nickel-iron hydroxides by microorganism corrosion for efficient oxygen evolution

Nickel–iron composites are efficient in catalyzing oxygen evolution. Here, we develop a microorganism corrosion approach to construct nickel–iron hydroxides. The anaerobic sulfate-reducing bacteria, using sulfate as the electron acceptor, play a significant role in the formation of iron sulfide decorated nickel–iron hydroxides, which exhibit excellent electrocatalytic performance for oxygen evolution. Experimental and theoretical investigations suggest that the synergistic effect between oxyhydroxides and sulfide species accounts for the high activity. This microorganism corrosion strategy not only provides efficient candidate electrocatalysts but also bridges traditional corrosion engineering and emerging electrochemical energy technologies.

Microbially influenced corrosion of carbon steel in the presence of anaerobic sulphate-reducing bacteria

ABSTRACTCarbon steel is currently being considered as a candidate canister material for use in a deep geological repository of radioactive waste. Assessment of canister material corrosion through microbial activity is an important part of the safety assessment for the final repository. The aim of study was to compare and characterise the corrosion behaviour of carbon steel under sterile and non-sterile anaerobic conditions in natural groundwater containing sulphate-reducing bacteria (SRB). A molecular-biological approach was used to determine the presence and abundance changes of relevant bacterial groups. Carbon steel corrosion rates were higher in the presence of SRB compared with sterile control. EIS described the evolution of three time-constants under non-sterile conditions, while scanning electron microscopy confirmed that the carbon steel surface was covered with a two-layer biofilm. Molecular-biological analysis of the water and biofilm indicated the dominance of SRB, with Desulfomicrobium and Desulfovibrio species prevalent.

Odor emission and microbial community succession during biogas residue composting covered with a molecular membrane

A membrane-covered composting system was used to investigate the odor emission and microbial community succession during biogas residue composting. Results showed that in comparison with the control (CK) group, the NH3 and H2S emissions outside the membrane of the membrane-covered (CT) group decreased by 58.64% and 38.13%, respectively. The nitrogen preservation rate of the CT group was increased by 17.27% in comparison with the CK group. Moreover, the ammonium nitrogen and nitrate nitrogen contents of the CT group were 37.68% and 11.77% higher than those of the CK group, respectively. Microbial analysis showed that the average abundance and co-occurrence rate of ammonification bacteria dominated by Pseudomonas and Bacillus in the CT group were lower than those in the CK group, and the abundance of anaerobic sulfate-reducing bacteria (SRB) dominated by Desulfovibrio in the CT group was higher than that in the CK group.