Diversity and activity of sulphur-oxidizing bacteria and sulphate-reducing bacteria in landfill cover soils

Sulfate-reducing bacteria unearthed: ecological functions of the diverse prokaryotic group in terrestrial environments

Sulfate-reducing prokaryotes (SRPs) are essential microorganisms that play crucial roles in various ecological processes. Even though SRPs have been studied for over a century, there are still gaps in our understanding of their biology. In the past two decades, a significant amount of data on SRP ecology has been accumulated. This review aims to consolidate that information, focusing on SRPs in soils, their relation to the rare biosphere, uncultured sulfate reducers, and their interactions with other organisms in terrestrial ecosystems. SRPs in soils form part of the rare biosphere and contribute to various processes as a low-density population. The data reveal a diverse range of sulfate-reducing taxa intricately involved in terrestrial carbon and sulfur cycles. While some taxa like Desulfitobacterium and Desulfosporosinus are well studied, others are more enigmatic. For example, members of the Acidobacteriota phylum appear to hold significant importance for the terrestrial sulfur cycle. Many aspects of SRP ecology remain mysterious, including sulfate reduction in different bacterial phyla, interactions with bacteria and fungi in soils, and the existence of soil sulfate-reducing archaea. Utilizing metagenomic, metatranscriptomic, and culture-dependent approaches will help uncover the diversity, functional potential, and adaptations of SRPs in the global environment.

Effects of operating conditions on the in situ control of sulfur-containing odors by using a novel alternative landfill cover and its transformation mechanism

Sulfur-containing gases are main sources of landfill odors, which has become a big issue for pollution to environment and human health. Biocover is promising for treating landfill odors, with advantages of durability and environmental friendliness. In this study, charcoal sludge compost was utilized as the main effective component of a novel alternative landfill cover and the in situ control of sulfur-containing odors from municipal solid waste landfilling process was simulated under nine different operating conditions. Results showed that five sulfur-containing odors (hydrogen sulfide, H2S; methyl mercaptan, CH3SH; dimethyl sulfide, CH3SCH3; ethylmercaptan, CH3CH2SH; carbon disulfide, CS2) were monitored and removed by the biocover, with the highest removal efficiencies of 77.18% for H2S, 87.36% for CH3SH, and 92.19% for CH3SCH3 in reactor 8#, and 95.94% for CH3CH2SH and 94.44% for CS2 in reactor 3#. The orthogonal experiment showed that the factors influencing the removal efficiencies of sulfur-containing odors were ranked from high to low as follows: temperature > weight ratio > humidity content. The combination of parameters of 20% weight ratio, 25°C temperature, and 30% water content was more recommended based on the consideration of the removal efficiencies and economic benefits. The mechanisms of sulfur conversion inside biocover were analyzed. Most organic sulfur was firstly degraded to reduced sulfides or element sulfur, and then oxidized to sulfate which could be stable in the layer as the final state. In this process, sulfur-oxidizing bacteria play a great role, and the distribution of them in reactor 1#, 5#, and 8# was specifically monitored. Bradyrhizobiaceae and Rhodospirillaceae were the dominant species which can utilize sulfide as substance to produce sulfate and element sulfur, respectively. Based on the results of OUTs, the biodiversity of these sulfur-oxidizing bacteria, these microorganisms, was demonstrated to be affected by the different parameters. These results indicate that the novel alternative landfill cover modified with bamboo charcoal compost is effective in removing sulfur odors from landfills. Meanwhile, the findings have direct implications for addressing landfill odor problems through parameter adjustment.

Thiothrix and Sulfurovum genera dominate bacterial mats in Slovak cold sulfur springs

Microbiota of sulfur-rich environments has been extensively studied due to the biotechnological potential of sulfur bacteria, or as a model of ancient life. Cold terrestrial sulfur springs are less studied compared to sulfur-oxidizing microbiota of hydrothermal vents, volcanic environments, or soda lakes. Despite that, several studies suggested that sulfur springs harbor diverse microbial communities because of the unique geochemical conditions of upwelling waters. In this study, the microbiota of five terrestrial sulfur springs was examined using a 16 S rRNA gene sequencing. The clear dominance of the Proteobacteria and Campylobacterota phyla of cold sulfur springs microbiota was observed. Contrary to that, the microbiota of the hot sulfur spring was dominated by the Aquificota and Firmicutes phylum respectively. Sulfur-oxidizing genera constituted a dominant part of the microbial populations with the Thiothrix and Sulfurovum genera identified as the core microbiota of cold sulfur terrestrial springs in Slovakia. Additionally, the study emphasizes that sulfur springs in Slovakia support unique, poorly characterized bacterial communities of sulfur-oxidizing bacteria.

Degradation of biogas in a simulated landfill cover soil at laboratory scale: Compositional changes of main components and volatile organic compounds

A laboratory experiment lasting 28 days was run to simulate a typical landfill system and to investigate the compositional changes affecting the main components (CH₄, CO₂, and H₂) and nonmethane volatile organic compounds from biogas generated by anaerobic digestion of food waste and passing through a soil column. Gas samples were periodically collected from both the digester headspace and the soil column at increasing distances from the biogas source. CH₄ and H₂ were efficiently degraded along the soil column. The isotopic values of δ¹³C measured in CH₄ and CO₂ from the soil column were relatively enriched in ¹³C compared to the biogas. Aromatics and alkanes were the most abundant groups in the biogas samples. Among these compounds, alkylated benzenes and long-chain C₃₊ alkanes were significantly degraded within the soil column, whereas benzene and short-chain alkanes were recalcitrant. Terpene and O-substituted compounds were relatively stable under oxidising conditions. Cyclic, alkene, S-substituted, and halogenated compounds, which exhibited minor amounts in the digester headspace, were virtually absent in the soil column. These results pointed out how many recalcitrant potentially toxic and polluting compounds tend to be relatively enriched along the soil column, claiming action to minimise diffuse landfill gas (LFG) emissions. The proposed experimental approach represents a reliable tool for investigating the attenuation capacities of landfill cover soils for LFG components and developing optimised covers by adopting proper soil treatments and operating conditions to improve their degradation efficiencies.

Elemental sulphur recovery from a sulphate-rich aqueous stream in a single hybrid linear flow channel reactor is mediated through microbial community dynamics and adaptation to reactor zones

The coupled application of biological sulphate reduction (BSR) and partial sulphide oxidation to treat sulphate-rich wastewater is an effective strategy to mitigate pollution and recover elemental sulphur for repurposing. The recent development of the hybrid linear flow channel reactor (LFCR) achieves simultaneous BSR and partial sulphide oxidation with biosulphur recovery via a floating sulphur biofilm (FSB). Here, we explore the microbial community zoning and dynamics facilitating the process. A total of three continuous LFCRs were used to evaluate the effect of reactor zones, hydraulic residence time (HRT), carbon source, namely lactate and acetate, as well as reactor geometry and scale on process performance and microbial community dynamics. Community composition of sessile and planktonic microbial consortia were resolved at a 5- and 2-day HRT through 16S rRNA amplicon sequencing. Preferential attachment and prevalence of specific phylotypes within the sessile and planktonic communities revealed clear adaptation of key microorganisms to different microenvironments. Key microbial taxa affiliated with sulphate reduction and sulphide oxidation as well as those implicated in fermentation and syntrophic metabolism, fluctuated in response to changes in HRT and process performance. Through understanding the relationship between microbial community dynamics and process performance, this research will inform better process design and optimization of the hybrid LFCR.

Use of methanotrophically activated biochar in novel biogeochemical cover system for carbon sequestration: Microbial characterization

Biochar-amended soils have been explored to enhance microbial methane (CH₄) oxidation in landfill cover systems. Recently, research priorities have expanded to include the mitigation of other components of landfill gas such as carbon dioxide (CO₂) and hydrogen sulfide (H₂S) along with CH₄. In this study, column tests were performed to simulate the newly proposed biogeochemical cover systems, which incorporate biochar-amended soil for CH₄ oxidation and basic oxygen furnace (BOF) slag for CO₂ and H₂S mitigation, to evaluate the effect of cover configuration on microbial CH₄ oxidation and community composition. Biogeochemical covers included a biochar-amended soil (10% w/w), and methanotroph-enriched activated biochar amended soil (5% or 10% w/w) as a biocover layer or CH₄ oxidation layer. The primary outcome measures of interest were CH₄ oxidation rates and the structure and abundance of methane-oxidation bacteria in the covers. All column reactors were active in CH₄ oxidation, but columns containing activated biochar-amended soils had higher CH₄ oxidation rates (133 to 143 μg CH₄ g^-1 day^-1) than those containing non-activated biochar-amended soil (50 μg CH₄ g^-1 day^-1) and no-biochar soil or control soil (43 μg CH₄ g^-1 day^-1). All treatments showed significant increases in the relative abundance of methanotrophs from an average relative abundance of 5.6% before incubation to a maximum of 45% following incubation. In activated biochar, the abundance of Type II methanotrophs, primarily Methylocystis and Methylosinus, was greater than that of Type I methanotrophs (Methylobacter) due to which activated biochar-amended soils also showed higher abundance of Type II methanotrophs. Overall, biogeochemical cover profiles showed promising potential for CH₄ oxidation without any adverse effect on microbial community composition and methane oxidation. Biochar activation led to an alteration of the dominant methanotrophic communities and increased CH₄ oxidation.

Metagenomics Analysis Reveals the Microbial Communities, Antimicrobial Resistance Gene Diversity and Potential Pathogen Transmission Risk of Two Different Landfills in China

In this study, we used a metagenomic approach to analyze microbial communities, antibiotic resistance gene diversity, and human pathogenic bacterium composition in two typical landfills in China. Results showed that the phyla Proteobacteria, Bacteroidetes, and Actinobacteria were predominant in the two landfills, and archaea and fungi were also detected. The genera Methanoculleus, Lysobacter, and Pseudomonas were predominantly present in all samples. sul2, sul1, tetX, and adeF were the four most abundant antibiotic resistance genes. Sixty-nine bacterial pathogens were identified from the two landfills, with Klebsiella pneumoniae, Bordetella pertussis, Pseudomonas aeruginosa, and Bacillus cereus as the major pathogenic microorganisms, indicating the existence of potential environmental risk in landfills. In addition, KEGG pathway analysis indicated the presence of antibiotic resistance genes typically associated with human antibiotic resistance bacterial strains. These results provide insights into the risk of pathogens in landfills, which is important for controlling the potential secondary transmission of pathogens and reducing workers’ health risk during landfill excavation.

Electrolysis-sulfate-reducing up-flow sludge bed-biological contact oxidation reactor for Norfloxacin removal from wastewater with high sulfate content

This study investigated the treatment of 100-mg/L Norfloxacin (NOR) wastewater containing high concentrations of sulfate through a combination of electrolysis, sulfate-reducing up-flow sludge bed (SRUSB), and biological contact oxidation reactor (BCOR) treatments. Results revealed that after 62 h, the reaction system had processed over 97% of the NOR. Additionally, electrolysis with sodium sulfate as the electrolyte transformed 87.8% of the NOR but only 33.5% of the total organic carbon (TOC). In the SRUSB, the TOC and SO₄^2- contents were simultaneously reduced by 87.4% and 95.6%, respectively, providing a stable environment to the BCOR. In the BCOR, 36.3% and 85.9% of the NOR and TOC were degraded. High-performance liquid chromatography-tandem mass spectrometry analysis identified three possible degradation pathways under the attack of -OH during electrolysis, including defluorination, piperazinyl ring transformation, and quinolone ring transformation. Furthermore, the Illumina HiSeq sequencing results demonstrated that the sulfate-reducing bacteria (represented by Desulfobacter and Desulfobulbus) in the SRUSB and the sulfate-oxidizing bacteria (mainly consisting of Gammaproteobacteria and Alphaproteobacteria) in the BCOR played important roles in carbon chain oxidation and benzene ring opening and thoroughly degraded the electrolysis products. Thus, this method effectively overcomes the incomplete degradation and low removal efficiency issues associated with single electrolysis or biological methods in traditional processes.

Reducing odor emissions from feces aerobic composting: additives

Aerobic composting is a reliable technology for treating human and animal feces, and converting them into resources. Odor emissions in compost (mainly NH₃ and VSCs) not only cause serious environmental problems, but also cause element loss and reduce compost quality. This review introduces recent progresses on odor mitigation in feces composting. The mechanism of odor generation, and the path of element transfer and transformation are clarified. Several strategies, mainly additives for reducing odors proven effective in the literature are proposed. The characteristics of these methods are compared, and their respective limitations are analyzed. The mechanism and characteristics of different additives are different, and the composting plant needs to be chosen according to the actual situation. The application of adsorbent and biological additives has a broad prospect in feces composting, but the existing research is not enough. In the end, some future research topics are highlighted, and further research is needed to improve odor mitigation and element retention in feces compost.

Aerobic composting is a reliable technology for treating human and animal feces, and converting them into resources. The addition of additives can reduce the production of odor during the composting process.

Novel sulphur-oxidizing bacteria consummate sulphur deficiency in oil seed crop

Plants absorb sulphate, the oxidized form of elemental sulphur (S°), from soil. Sulphur-oxidizing bacteria play a key role in transformation of sulphur in soil. Oil seed crops require high amount of sulphur and it plays an important role in the formation of proteins, vitamins and enzymes. It increases yield, oil content and protein content in oil seed crops. Sulphur is the important constituent of amino acids, viz. methionine, cystine, and cysteine. It necessitates various enzymatic, metabolic processes such as photosynthesis and nitrogen fixation. In the last few years, the prominence of sulphur in oil seed crop nutrition has been accepted as widespread occurrence of its inadequacy in agricultural soil. Approximately 41% of Indian soil is deficient in sulphur. The soil microbial population is the major enforcement behind sulphur transformation. They mineralize, immobilize, oxidize and reduce the elemental and other reduced forms of sulphur. The main step in transformation is oxidation carried out by microorganisms to convert sulphur into sulphate. The chemolithotrophic bacteria belonging to genus Thiobacillus are of primary importance; there are heterotrophic bacteria also which can oxidize sulphur in soil. The pH reduction at the time of oxidation helps in mineralization and absorption of other essential nutrients also. This property of sulphur-oxidizing bacteria (SOB) shows their potential to be used as bioinoculants. Bioformulations prepared using carrier-based formulations, immobilization, biostimulation, etc., are sustainable forms of fertilizers. These SOB inoculants can be used to increase the fertility and sulphate production in soil.

Emission characteristics and health risk assessment of VOCs from a food waste anaerobic digestion plant: A case study of Suzhou, China

The process of anaerobic digestion in food waste treatment plants generates a large amount of volatile organic compounds (VOCs). Long-term exposure to this exhaust gas can pose a threat to the health of workers and people living nearby. In this study, VOCs emitted from different working units in a food waste anaerobic digestion plant were monitored for a year. Variations in VOCs emitted from each unit were analyzed and a health risk assessment was conducted for each working unit. The results show that the concentration of VOCs in different units varied greatly. The highest cumulative concentration of VOCs appeared in the hydrothermal hydrolysis unit (3.49 × 10⁴ μg/m³), followed by the sorting/crushing room (8.97 × 10³ μg/m³), anaerobic digestion unit (6.21 × 10² μg/m³), and biogas production unit (2.01 × 10² μg/m³). Oxygenated compounds and terpenes were the major components of the emitted VOCs, accounting for more than 98% of total VOC emissions. The carcinogenic risk in the plant exceeded the safety threshold (ILCR<1 × 10^-6), while the non-carcinogenic risk was within the acceptable range (HI < 1). The carcinogenic risk from the hydrothermal hydrolysis unit was the highest, reaching 4.4 × 10^-5, and was labeled as "probable risk." The carcinogenic risk at the plant boundary was 1.2 × 10^-5, indicating exhaust gases can cause a health threat to neighbors. Therefore, management VOCs in anaerobic digestion plants should receive more attention, and employees should minimize the time they spend in the hydrothermal hydrolysis unit.

Diversity of Sulfur-oxidizing Bacteria at the Surface of Cattle Manure Composting Assessed by an Analysis of the Sulfur Oxidation Gene soxB

Sulfur-oxidizing bacterial diversity at the surface of cattle manure was characterized throughout the composting process using a sulfur oxidation gene (soxB) clone library approach. In the mesophilic phase, clones related to the genera Hydrogenophaga and Hydrogenophilus were characteristically detected. In the thermophilic phase, clones related to the genera Hydrogenophaga and Thiohalobacter were predominant. In the cooling phase, the predominant soxB sequences were related to the genus Pseudaminobacter and a new sulfur-oxidizing bacterium belonging to the class Alphaproteobacteria. The present study showed changes in the community composition of sulfur-oxidizing bacteria at the surface of compost throughout the composting process.

Effects of biochar on bacterial communities in a newly established landfill cover topsoil

Recent studies revealed the benefits of applying biochar in landfill final cover soil, such as adsorbing odorous compounds and promoting microbial methane oxidation. Most of these processes are related to the soil bacterial communities. However, the effects of biochar application on the overall bacterial community in newly established landfill cover soil are not yet understood, especially in field condition. The objective of the present field study is to investigate the effects of biochar on the diversity of soil bacterial community 3 months after incubation (short-term). Landfill final cover topsoil (0.6 m) was amended with 0 (control), 5, and 10% (w/w) of biochar derived from peanut-shell and wheat straw. Soil bacterial communities were analysed using the 16S rRNA-based T-RFLP approach. Biochar application significantly (p < 0.05) increased the diversity of soil bacterial communities. The Shannon diversity index of bacterial communities in soil amended with 5 and 10% of biochar was increased from 3.34 to 3.85 and 3.92, respectively. There were four bacterial phyla recorded found at both control and amended soils, namely Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. In addition, Gemmatimonadetes was found only in soil amended with 10% biochar. The interactions between soil bacterial communities and measured soil parameters including moisture content, electrical conductivity, total organic matter, total nitrogen and total phosphorus were found to be statistically non-significant (p > 0.05), according to the canonical correspondence analysis (CCA). This may be due to the highly heterogeneous nature of landfill soil. Results from this study revealed that short-term biochar application already altered the soil physicochemical properties and increased the diversity of soil bacterial communities.

Odor removal by and microbial community in the enhanced landfill cover materials containing biochar-added sludge compost under different operating parameters

Odor problem has become a growing concern for municipal solid waste (MSW) operators and communities located close to landfill sites. In this study, nine laboratory-scale landfill reactors were used to simulate in-situ odor control by a novel landfill cover material consisting of biochar-added sludge compost under various operating parameters. Characterization of odor removal and microbial community in the cover layer under various operating parameters was conducted using gas chromatograph-mass spectrometry and 454 high-throughput pyrosequencing, respectively. Results showed that H₂S (76.9-86.0%) and volatile organic sulfur compounds (VOSCs) (12.3-21.7%) were dominant according to their theoretical generated odor concentrations. The total odor REs calculated using the theoretical odor concentrations in the landfill reactors were different than using the measured odor values, which were ranked from high to low as: R6 > R5 > R7 > R4 > R8 > R9 > R3 > R2 > R1, showing the largest discrepancy of 25.3%. The optimum combination of operating parameters based on the theoretical odor concentration was different with that based on the measured odor concentrations. Moreover, although Firmicutes (12.21-91.48%), Proteobacteria (3.55-51.03%), and Actinobacteria (4.01-47.39%) were in general the three major bacterial phyla found in the landfill covers, the detailed bacterial communities in the cover materials of the simulated reactors varied with various operating parameters. Alicyclobacillus and Tuberibacillus showed positive correlations with the removal efficiencies (REs) of chlorinated compounds, H₂S, aromatic compounds, volatile organic sulfur compounds (VOSCs), and organic acids. The correlations of Rhodanobacter, Gemmatimonas, Flavisolibacter and Sphingomonas were strongly positive with ammonia RE and relatively positive with REs of organic acids, VOSCs, and aromatic compounds. These findings are instrumental in understanding the relationship between the structure of microbial communities and odor removal performances, and in developing techniques for in-situ odor control at landfills.

Impacts of Human Activities on the Composition and Abundance of Sulfate-Reducing and Sulfur-Oxidizing Microorganisms in Polluted River Sediments

Water system degradation has a severe impact on daily life, especially in developing countries. However, microbial changes associated with this degradation, especially changes in microbes related to sulfur (S) cycling, are poorly understood. In this study, the abundance, structure, and diversity of sulfate-reducing microorganisms (SRM) and sulfur-oxidizing microorganisms (SOM) in the sediments from the Ziya River Basin, which is polluted by various human interventions (urban and agricultural activities), were investigated. Quantitative real-time PCR showed that the S cycling-related (SCR) genes (dsrB and soxB) were significantly elevated, reaching 2.60 × 10⁷ and 1.81 × 10⁸ copies per gram of dry sediment, respectively, in the region polluted by human urban activities (RU), and the ratio of dsrB to soxB abundance was significantly elevated in the region polluted by human agricultural activities (RA) compared with those in the protected wildlife reserve (RP), indicating that the mechanisms underlying water system degradation differ between RU and RA. Based on a 16S rRNA gene analysis, human interventions had substantial effects on microbial communities, particularly for microbes involved in S cycling. Some SCR genera (i.e., Desulfatiglans and Geothermobacter) were enriched in the sediments from both RA and RU, while others (i.e., Desulfofustis and Desulfonatronobacter) were only enriched in the sediments from RA. A redundancy analysis indicated that NH₄⁺-N and total organic carbon significantly influenced the abundance of SRM and SOM, and sulfate significantly influenced only the abundance of SRM. A network analysis showed high correlation between SCR microorganisms and other microbial groups for both RU and RA, including those involved in carbon and metal cycling. These findings indicated the different effects of different human interventions on the microbial community composition and water quality degradation.

Emission characteristics and health risk assessment of volatile organic compounds produced during municipal solid waste composting

Municipal solid waste degradation during composting generates volatile organic compounds (VOCs), which can pose health risks the staff at the composting site and people living nearby. This problem restricts the widespread application of composting techniques. The characteristics of VOCs emitted from different units at a composting plant and the health risks posed were investigated in this study. A total of 44 VOCs (including alkanes, alkenes, aromatic compounds, halogenated compounds, oxygenated compounds, and sulfur-containing compounds) were identified and quantified. The highest VOC concentration (15484.1 ± 785.3 µg/m³) was found in primary fermentation, followed by the tipping unit (10302.1 ± 1334.8 µg/m³), composting product (4693.6 ± 1024.3 µg/m³), secondary fermentation (929.9 ± 105.2 µg/m³), and plant boundary (370.4 ± 75.8 µg/m³). The mean VOC concentration was 6356.0 µg/m³. The main compounds emitted during primary fermentation were oxygenated and those emitted from the tipping unit were alkenes. Health risk assessments indicate that VOCs did not pose unacceptable non-carcinogenic risks i.e., the HR values were <1 and carcinogenic risks (CR) values were <1.0 × 10^-4. These results indicate that VOC emissions do not pose health risks to the staff at the composting site or to people living nearby. However, the cumulative non-carcinogenic and carcinogenic risks posed by the VOC mixture were high, especially for the primary fermentation unit emissions. Therefore, protecting the staff working near the primary fermentation unit should be a priority. Measures should be taken to minimize cumulative non-carcinogenic and carcinogenic risks because people are exposed to a mixture of VOCs mixture rather than to a single type of VOC.

Biogeochemical oxidation of calcium sulfite hemihydrate to gypsum in flue gas desulfurization byproduct using sulfur-oxidizing bacteria

Flue gas desulfurization (FGD) is a well-established air treatment technology for coal and oil combustion gases that commonly uses lime or pulverized limestone aqueous slurries to precipitate sulfur dioxide (SO₂) as crystalline calcium salts. Under forced oxidation (excess oxygen) conditions, FGD byproduct contains almost entirely (>92%) gypsum (CaSO₄·2H₂O), a useful and marketable commodity. In contrast, FGD byproduct formed in oxygen deficient oxidation systems contains a high percentage of hannebachite (CaSO₃·0.5H₂O) to yield a material with no commercial value, poor dewatering characteristics, and that is typically disposed in landfills. Hannebachite in FGD byproduct can be chemically converted to gypsum; however, the conditions that support rapid formation of gypsum require large quantities of acids or oxidizers. This work describes a novel, patent pending application of microbial physiology where a natural consortium of sulfur-oxidizing bacteria (SOB) was used to convert hannebachite-enriched FGD byproduct into a commercially valuable, gypsum-enriched product (US Patent Assignment 503373611). To optimize the conversion of hannebachite into gypsum, physiological studies on the SOB were performed to define their growth characteristics. The SOB were found to be aerobic, mesophilic, neutrophilic, and dependent on a ready supply of ammonia. They were capable of converting hannebachite to gypsum at a rate of approximately five percent per day when the culture was applied to a 20 percent FGD byproduct slurry and SOB growth medium. 16S rDNA sequencing revealed that the SOB consortium contained a variety of different bacterial genera including both SOB and sulfate-reducing bacteria. Halothiobacillus, Thiovirga and Thiomonas were the dominant sulfur-oxidizing genera.

Methanethiol generation potential from anaerobic degradation of municipal solid waste in landfills

Volatile sulfur compounds are the main odorants at landfills. In this study, methanethiol (CH₃SH) was chosen as a typical volatile organic sulfur compound, and its generation potential was investigated during the anaerobic degradation of the organic fractions of municipal solid waste (MSW) including rice, flour food, vegetable, fish and pork, paper, cellulose textile, and yard wastes. Among the experimental wastes, gas generation was the highest in the fish and pork waste with a high CH₃SH concentration of up to 2.5% (v/v). Sulfur reduction in the solid phase was mostly converted into gaseous sulfur compounds. During the whole experiment, the cumulative CH₃SH generation from the fish and pork waste was 0.139 L kg_dw^-1, which was about 2 and 6 orders of magnitude higher than that from the other experimental wastes. The ratio of CH₃SH-S to TS reduction was 31.56% in the fish and pork waste. These results would be helpful to understand the generation of volatile sulfur compounds during the anaerobic degradation of MSW and develop techniques to control odor pollution at landfills.

Elimination of ethanethiol released from municipal wastes by absorption sequencing electrochemical oxidation

As a typical municipal waste landfill gas, ethanethiol can become an air pollutant because of its low odor threshold concentration and toxicity to human beings. A hybrid process of absorption combined with electrochemical oxidation to degrade ethanethiol was investigated. The ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF₄) was employed as an absorbent to capture ethanethiol from the air stream. Electrochemical oxidation demonstrated that ethanethiol could be oxidized on a β-PbO₂ anode modified with fluoride, while [BMIM]BF₄ was used as an electrolyte. After a reaction time of 90 min under a current density of 50 mA/cm², ethanethiol could be thoroughly destructed by the successive attack of hydroxyl radicals (·OH) electrogenerated on the surface of the β-PbO₂ anode, while the sulfur atoms in ethanethiol were ultimately converted to sulfate ions [Formula: see text]. The reaction mechanism is proposed, and the operating condition is also estimated with a kinetic model. This hybrid process could be a promising way to remove thiol compounds from municipal waste landfill gases.

Compositions and Abundances of Sulfate-Reducing and Sulfur-Oxidizing Microorganisms in Water-Flooded Petroleum Reservoirs with Different Temperatures in China

Sulfate-reducing bacteria (SRB) have been studied extensively in the petroleum industry due to their role in corrosion, but very little is known about sulfur-oxidizing bacteria (SOB), which drive the oxidization of sulfur-compounds produced by the activity of SRB in petroleum reservoirs. Here, we surveyed the community structure, diversity and abundance of SRB and SOB simultaneously based on 16S rRNA, dsrB and soxB gene sequencing, and quantitative PCR analyses, respectively in petroleum reservoirs with different physicochemical properties. Similar to SRB, SOB were found widely inhabiting the analyzed reservoirs with high diversity and different structures. The dominant SRB belonged to the classes Deltaproteobacteria and Clostridia, and included the Desulfotignum, Desulfotomaculum, Desulfovibrio, Desulfobulbus, and Desulfomicrobium genera. The most frequently detected potential SOB were Sulfurimonas, Thiobacillus, Thioclava, Thiohalomonas and Dechloromonas, and belonged to Betaproteobacteria, Alphaproteobacteria, and Epsilonproteobacteria. Among them, Desulfovibrio, Desulfomicrobium, Thioclava, and Sulfurimonas were highly abundant in the low-temperature reservoirs, while Desulfotomaculum, Desulfotignum, Thiobacillus, and Dechloromonas were more often present in high-temperature reservoirs. The relative abundances of SRB and SOB varied and were present at higher proportions in the relatively high-temperature reservoirs. Canonical correspondence analysis also revealed that the SRB and SOB communities in reservoirs displayed high niche specificity and were closely related to reservoir temperature, pH of the formation brine, and sulfate concentration. In conclusion, this study extends our knowledge about the distribution of SRB and SOB communities in petroleum reservoirs.

Control of dimethyl sulfide and dimethyl disulfide odors during pig manure composting using nitrogen amendment

Effects of nitrogen electron acceptors on dimethyl sulfide (Me₂S) and dimethyl disulfide (Me₂SS) odor emission during composting was investigated. The chemicals and doses used included sodium nitrate (NO₃^- at 10mM, 20mM and 40mM), sodium nitrite (NO₂^- at 10mM, 20mM and 40mM) and sodium nitrite (10mM, 20mM and 40mM) with hexaammonium heptamolybdate tetrahydrate (HHT). The results showed that the addition of these chemicals restricted the emission of Me₂S and Me₂SS. The emission reduction effect of NO₂^- was greater than NO₃^- at the same dosage. A greater reduction was observed when HHT was also added. With 2mM HHT+40mM NO₂^- addition, the emission of Me₂S and Me₂SS was reduced by 92.3% and 82.3%, respectively. Comparison of compost maturity indices for treated and untreated composts indicated that none of the additives adversely affected compost quality. These results indicate that nitrogen chemical addition may provide an efficient method to control sulfur odors during composting.

Sulfate reduction in microorganisms-recent advances and biotechnological applications

Sulfur, the least common of the five macroelements, plays an important role in biochemistry due to its ability to be easily reduced or oxidized, leading to a great amount of research concerning sulfur bioconversion. Interestingly, new studies concerning microbial sulfate reduction pathways in the last half decade have become increasingly sparse, indicating that most of the pathways involved have been discovered and studied. Despite this, systems biology approaches to model these pathways are often missing or not used. As the products of microbial sulfate reduction play important roles in the environment, biotechnology, and industry, modeling sulfur bioconversion remains an untapped research space for future work.

Immunotoxicity of skin acid secretion produced by the sea slug Berthellina citrina in mice spleen: Histological and Immunohistochemical study

Acid secretion containing sulfuric and hydrochloric acids is a fascinating defensive phenomenon within many groups of marine organisms. This study aimed to investigate the mice spleen histology and immunotoxicity using skin acid secretion (SAS) of the sea slug Berthellina citrina after oral administration. The spleen showed atrophy in the white pulp, decrease in the splenocytes density, megakaryocytes cytoplasmic degeneration as well as inflammatory cells infiltrations. The white and red pulp splenocytes number decreased time-dependently in the treated spleens. Additionally, the size of the megakaryocytes increased as compared with the control. The administration with SAS increased the number of the IgA(+) cells aggregation in the splenic red pulp. Furthermore, after 7days of the administration, large number of dispersed IgA(+) cells were distributed in splenic parenchyma. The IgA(+) cells numbers increased time-dependently as compared with those in the control. The aggregation sizes and number of the F4/80(+) cell in the splenic red pulp were increased. Furthermore the F4/80(+) cells numbers increased time-dependently as compared with those in the control. The UEAI(+) cells were found as free cells but not in aggregations in the control splenic red pulp. Contradictory to the number of IgA(+) cells and F4/80(+) cells the number of the UEAI(+) cells decreased time-dependently after administration with SAS. Hematologically, abnormal numbers of WBCs different cells were observed after administration with SAS. This study provides new insight about the toxicity of a marine extract may be used in natural products industry or medical applications.

Survey of Microbial Diversity in Flood Areas during Thailand 2011 Flood Crisis Using High-Throughput Tagged Amplicon Pyrosequencing

The Thailand flood crisis in 2011 was one of the largest recorded floods in modern history, causing enormous damage to the economy and ecological habitats of the country. In this study, bacterial and fungal diversity in sediments and waters collected from ten flood areas in Bangkok and its suburbs, covering residential and agricultural areas, were analyzed using high-throughput 454 pyrosequencing of 16S rRNA gene and internal transcribed spacer sequences. Analysis of microbial community showed differences in taxa distribution in water and sediment with variations in the diversity of saprophytic microbes and sulfate/nitrate reducers among sampling locations, suggesting differences in microbial activity in the habitats. Overall, Proteobacteria represented a major bacterial group in waters, while this group co-existed with Firmicutes, Bacteroidetes, and Actinobacteria in sediments. Anaeromyxobacter, Steroidobacter, and Geobacter were the dominant bacterial genera in sediments, while Sulfuricurvum, Thiovirga, and Hydrogenophaga predominated in waters. For fungi in sediments, Ascomycota, Glomeromycota, and Basidiomycota, particularly in genera Philipsia, Rozella, and Acaulospora, were most frequently detected. Chytridiomycota and Ascomycota were the major fungal phyla, and Rhizophlyctis and Mortierella were the most frequently detected fungal genera in water. Diversity of sulfate-reducing bacteria, related to odor problems, was further investigated using analysis of the dsrB gene which indicated the presence of sulfate-reducing bacteria of families Desulfobacteraceae, Desulfobulbaceae, Syntrobacteraceae, and Desulfoarculaceae in the flood sediments. The work provides an insight into the diversity and function of microbes related to biological processes in flood areas.