Reduced Sulfur Compounds Research Articles

Thiobacillus sedimenti sp. nov., a chemolithoautotrophic sulphur-oxidizing bacterium isolated from freshwater sediment.

A sulphur-oxidizing bacterium, designated strain SCUT-2T, was isolated from freshwater sediment collected from the Pearl River in Guangzhou, PR China. This strain was an obligate chemolithoautotroph, utilizing reduced sulphur compounds (elemental sulphur, thiosulphate, tetrathionate and sulphite) as the electron donor. Growth of strain SCUT-2T was observed at 20-40℃ (optimum at 30°C), pH 5.0-9.0 (optimum at 6.0), and NaCl concentration range of 0-9gL-1 (optimum at 1gL-1). The major cellular fatty acids were C16:0 ω7c and cyclo-C17:0. The DNA G + C content of the complete genome sequence was 66.8 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain SCUT-2T formed a lineage within the genus Thiobacillus, showing gene sequence identity of 98.0% with its closest relative Thiobacillus thioparus THI 115. The genome of strain SCUT-2T contains multiple genes encoding sulphur-oxidizing enzymes that catalyse the oxidation of reduced sulphur compounds, partial genes that are necessary for denitrification, and the genes encoding cbb3-type cytochrome c oxidase, aa3-type cytochrome c oxidase and bd-type quinol oxidase. Facultative anaerobic growth occurs when using nitrate as the electron acceptor and thiosulphate as the electron donor. On the basis of phenotypic, chemotaxonomic, genotypic and phylogenetic analysis, strain SCUT-2T (= GDMCC 1.4108T = JCM 39443T) is deemed to represent a novel Thiobacillus species, for which we propose the name Thiobacillus sedimenti sp. nov.

Bioprocessing of reduced sulfur compounds enhanced by treated wastewater with an alkaliphilic sulfur-oxidizing microbial consortium

An alkaliphilic sulfur-oxidizing bacterial consortium enrichment in synthetic media and supplemented treated wastewater was evaluated by measuring for thiosulfate biological oxidation and detailed analysis of the structure and function of the resultant bacterial communities. Aerobic batch assays revealed that cultures enriched with treated wastewater exhibited thiosulfate oxidation rates 17% faster than cultures in synthetic medium, attributed to the influence of inorganic and organic compounds present in the wastewater. Furthermore, cultures with treated wastewater demonstrated a 55% higher sulfate production rate than cultures with synthetic medium, probably due to specific intermediates generated during the oxidation process. 16S rRNA gene sequencing revealed greater microbial diversity in cultures with treated wastewater compared to cultures in synthetic medium, with Thioalkalivibrio prevailing as the dominant genus in both. Other genera, such as Planktosalinus, Aliidiomarina, Roseinatronobacter, and Azoarcus, were also identified; however, their relative abundances were associated with the available carbon sources in each medium. Functional analysis revealed a predominance of genes associated with thiosulfate and sulfide oxidation, emphasizing the significant role of the SOX system within cultures. The findings suggest the potential of treated wastewater to enrich an alkaliphilic sulfur-oxidizing bacterial consortia for biotechnological treatment of reduced sulfur compounds.

Coal Ash Triggers an Elevated Temperature Landfill Development: Lessons from the Bristol Virginia Solid Waste Landfill Neighboring Community

Landfills for disposing of solid waste are designed, located, managed, and monitored facilities expected to comply with government regulations to prevent contamination of the surrounding environment. After the average life expectancy of a typical landfill (30 to 50 years), a large investment in the construction, operation, final closure, and 30-year monitoring of a new site is needed. In this case study, we provide a holistic explanation of the unexpected development of elevated temperature landfills (ETLFs), such as that in the city of Bristol (United States) on the border of the states of Virginia and Tennessee, including the initial role played by coal ash. Despite the increasing frequency of ETLF occurrence, there is limited knowledge available about their associated environmental problems. The study uses mixed (qualitative, quantitative, and mapping) methods to analyze (1) the levels of odoriferous reduced sulfur compounds, ammonia, and volatile organic compounds (VOCs) emitted, (2) the ratio of methane to carbon dioxide concentrations in five locations, which dropped from unity (normal landfill) to 0.565, (3) the location of gas well heads with gradients of elevated temperatures, and (4) the correlation of the filling rate (upward of ~12 m y−1) with depth for registered events depositing coal ash waste. The work identifies spatial patterns that support the conclusion that coal ash served as the initiator for an ETLF creation. The case of the city of Bristol constitutes an example of ETLFs with elevated temperatures above the regulatory United States Environmental Protection Agency (EPA) upper threshold (65 °C), having alongside low methane emissions, large production of leachate, land subsidence, and a large production of organic compounds. Such landfills suffer abnormal chemical reactions within the waste mass that reduce the life expectancy of the site. Residents in such communities suffer intolerable odors from fugitive emissions and poor air quality becomes prominent, affecting the well-being and economy of surrounding populations. Conclusive information available indicates that the Bristol landfill has been producing large amounts of leachate and hazardous gases under the high pressures and temperatures developed within the landfill. A lesson learned, which should be used to prevent this problem in the future, is that the early addition of coal ash into the landfill would have catalyzed the process of ETLF creation. The work considers the public health risks and socioeconomic problems of residents exposed to emissions from an ETLF and discusses the efforts needed to prevent further incidents in other locations.

Oxyplasma meridianum gen. nov., sp. nov., an extremely acidophilic organotrophic member of the order Thermoplasmatales.

A mesophilic, hyperacidophilic archaeon, strain M1T, was isolated from a rock sample from Vulcano Island, Italy. Cells of this organism were cocci with an average diameter of 1 µm. Some cells possessed filaments. The strain grew in the range of temperatures between 15 and 52 °C and pH 0.5-4.0 with growth optima at 40 °C and pH 1.0. Strain M1T was aerobic and chemoorganotrophic, growing on complex substrates, such as casamino acids, trypticase, tryptone, yeast and beef extracts. No growth at expenses of oxidation of elemental sulphur or reduced sulphur compounds, pyrite, or ferrous sulphate was observed. The core lipids were glycerol dibiphytanyl glycerol tetraether lipids (membrane spanning) with 0 to 4 cyclopentane moieties and archaeol, with trace amounts of hydroxy archaeol. The dominant quinone was MK-7 : 7. The genome size of M1T was 1.67 Mbp with a G+C content of 39.76 mol%, and both characteristics were well within the common range for Thermoplasmatales. The phylogenetic analysis based on 16S rRNA gene sequence placed the strain M1T within the order Thermoplasmatales with sequence identities of 90.9, 90.3 and 90.5% to the closest SSU rRNA gene sequences from organisms with validly published names, Thermoplasma acidophilum, Thermoplasma volcanium and Thermogymnomonas acidicola, respectively. Based on the results of our genomic, phylogenetic, physiological and chemotaxonomic studies, we propose that strain M1T (=DSM 116605T=JCM 36570T) represents a new genus and species, Oxyplasma meridianum gen. nov., sp. nov., within the order Thermoplasmatales.

Wastewater Treatment with Bacterial Representatives of the Thiothrix Morphotype.

Bacteria of the Thiothrix morphotype, comprising the genera Thiothrix, Thiolinea and Thiofilum, are frequently encountered in domestic and industrial wastewater treatment systems, but they are usually not clearly differentiated due to the marked similarity in their morphologies. Methods ranging from light microscopy, FISH and PCR to modern high-throughput sequencing are used to identify them. The development of these bacteria in wastewater treatment systems has both advantages and disadvantages. On the one hand, the explosive growth of these bacteria can lead to activated sludge bulking or clogging of the treatment system's membranes, with a consequent decrease in the water treatment efficiency. On the other hand, members of the Thiothrix morphotype can improve the quality of granular sludge and increase the water treatment efficiency. This may be due to their capacity for sulfide oxidation, denitrification combined with the oxidation of reduced sulfur compounds, enhanced biological phosphate removal and possibly denitrifying phosphate removal. The recently obtained pangenome of the genus Thiothrix allows the explanation, at the genomic level, of the experimental results of various studies. Moreover, this review summarizes the data on the factors affecting the proliferation of representatives of the Thiothrix morphotype.

Effect of intensive seasonal pumping and recharge on sulfur biogeochemistry in groundwater of agricultural riparian zones

Physico-chemical characteristics of groundwater are often impacted by agricultural practices such as land use, fertilizer types, and groundwater pumping. This study aimed to identify contaminant sources and redox processes controlling the hydrogeochemistry of groundwater in riparian zones influenced by intensive agricultural activities, focusing on sulfur species. Groundwater samples were collected bimonthly from March 2014 to March 2015 from groundwater wells in two zones in South Korea with different agricultural systems. The water isotopic compositions of the groundwater indicated that all groundwater originated from the same meteoric water. Groundwater samples affected by periodic groundwater pumping exhibited wide variations in Mn2+ (47.8 ± 18.2 μM) and Fe2+ (123 ± 61.0 μM) and elevated SO42−, while NO3− was below the detection limit. Groundwater chemistry was affected by fertilizer and manure, and denitrification. The oxidation of reduced sulfur compounds by oxygen and nitrate did not fully account for the elevated SO42− concentrations and isotopic composition of sulfate (δ34S and δ18O) in the investigated aquifers. Therefore, we postulate that water level change due to periodic groundwater pumping and recharge enabled oxidants (MnO2 and Fe3+) to also contribute to oxidation of reduced sulfur. Additionally, fertilizers with distinct δ34S values and bacterial sulfate reduction (BSR) affected groundwater chemistry and its sulfur species, including δ34SSO4 and δ18OSO4. Removal of sulfate from the aquifer during pumping limited BSR. Consequently, the agricultural practices may further increase sulfate concentrations in the groundwater. This environmental impact should be thoroughly managed because high sulfate concentrations in drinking water cause ingestion problems in humans.

What kind of corrosion products are “black spots”? —Effects of reduced sulfur compounds on corrosion of bronze artefacts

While deterioration due to the generation of “black spots” is reported, consensus on the specific corrosion products comprising black spots and underlying deterioration mechanisms is lacking. This study investigated the deterioration of copper objects by analysing the black spots that appeared on them and proposes environmental conditions to suppress the appearance of black spots. Bronze artefacts excavated from a marine archaeological site, on which black spots were generated, were closely observed, and investigated. First, X-ray fluorescence and micro-X-ray diffraction analyses were performed on a bronze artefact, from which the black spots were removed, to determine the composition of the artefact. Second, to investigate the composition of the black spots, fine structure analysis of the black spots on the fine fragments of the bronze artefacts was conducted using scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy, and electron diffraction (ED) analysis. The results indicate that the black spots were partially composed of metallic copper and a fine particle mixture of Cu2S and CuSO4. These results imply that the transformation of copper sulfide to metallic copper may have played an important role in the initiation and propagation of black spots. In this study, ED analysis was performed on the microscopic area of the black spots; no amorphous phases were detected, and all observed phases were identified as crystalline materials. To determine the sources of gas-phase sulfur compounds that cause black spots, H2S and carbonyl sulfide (COS) emissions from a spherical clay artefact (a cannon ball with gunpowder excavated from an underwater archaeological site) which was exhibited in the same showcase with the bronze artefacts were analysed via gas chromatography. The concentrations of H2S and COS were 0.462 and 8.636 ppb, respectively; these are significantly higher than those in the lower troposphere. These results indicate that deterioration by black spots occurred because of H2S and COS, which were emitted from the spherical clay artefact excavated from an underwater archaeological site in the exhibition case. In addition, it was confirmed that the inclusion of deoxygenating and dehumidifying agents (RP-AN) in the plastic bag in which the spherical clay artefact was inserted resulted in a significant decrease in the concentration of H2S and COS.

Desulfurising Fuels Using Alcohol-Based Deep Eutectic Solvents Using Extractive Catalytic Oxidative Desulfurisation Method

Removal of sulfur compounds from transportation fuels is a requirement in the worldwide effort to reduce emissions from transportation fuels. Refineries use the hydrodesulfurisation (HDS) process to reduce sulfur compounds in fuels. However, the HDS process requires high hydrogen pressure and temperature, making it costly. An alternative to the HDS process is oxidative desulfurisation via solvent extraction, which requires low-temperature operating conditions. In this regard, deep eutectic solvents (DESs) are attractive for researchers to desulfurise transportation fuels via solvent extraction due to their low-cost. In our study, DESs were synthesised using phenylacetic acid (PAA) and salicylic acid (SAA) as hydrogen bond acceptors (HBAs) and tetraethylene glycol (TTEG) as hydrogen bond donor (HBD) in the mole ratio of 1:2. DESs were characterised by using Fourier transform infrared (FTIR) spectroscopy. Physicochemical properties of DESs, such as density, viscosity and refractive index, were also measured. The synthesised DESs were used to extract organosulfur compounds from model fuel and actual diesel. An oxidation study was carried out for model fuel and diesel, followed by solvent extraction using these synthesised DESs. The extraction efficiency for PAA/TTEG(1:2) and SAA/TTEG(1:2) was achieved as 50.16% and 38.89% for model fuel at a temperature of 30°C using a solvent to feed ratio of 1.0 while for diesel, it was 38% and 37%. However, it increased to 77%, 68% and 54%, 73%, respectively, for PAA/TTEG(1:2) and SAA/TTEG(1:2) when the feedstocks were oxidised. These results showed better extraction performance of DES PAA/TTEG(1:2) than that of SAA/TTEG(1:2) at low temperature 30°C using combined extractive catalytic oxidative desulfurisation. Hence, the DES synthesised using SAA and TTEG in the molar ratio of 1:2 works better as an extraction solvent for removing organic sulfur compounds from fuels at low temperatures.

SoxY gene family expansion underpins adaptation to diverse hosts and environments in symbiotic sulfide oxidizers.

Sulfur-oxidizing bacteria (SOB) have developed distinct ecological strategies to obtain reduced sulfur compounds for growth. These range from specialists that can only use a limited range of reduced sulfur compounds to generalists that can use many different forms as electron donors. Forming intimate symbioses with animal hosts is another highly successful ecological strategy for SOB, as animals, through their behavior and physiology, can enable access to sulfur compounds. Symbioses have evolved multiple times in a range of animal hosts and from several lineages of SOB. They have successfully colonized a wide range of habitats, from seagrass beds to hydrothermal vents, with varying availability of symbiont energy sources. Our extensive analyses of sulfur transformation pathways in 234 genomes of symbiotic and free-living SOB revealed widespread conservation in metabolic pathways for sulfur oxidation in symbionts from different host species and environments, raising the question of how they have adapted to such a wide range of distinct habitats. We discovered a gene family expansion of soxY in these genomes, with up to five distinct copies per genome. Symbionts harboring only the "canonical" soxY were typically ecological "specialists" that are associated with specific host subfamilies or environments (e.g., hydrothermal vents, mangroves). Conversely, symbionts with multiple divergent soxY genes formed versatile associations across diverse hosts in various marine environments. We hypothesize that expansion and diversification of the soxY gene family could be one genomic mechanism supporting the metabolic flexibility of symbiotic SOB enabling them and their hosts to thrive in a range of different and dynamic environments.IMPORTANCESulfur metabolism is thought to be one of the most ancient mechanisms for energy generation in microorganisms. A diverse range of microorganisms today rely on sulfur oxidation for their metabolism. They can be free-living, or they can live in symbiosis with animal hosts, where they power entire ecosystems in the absence of light, such as in the deep sea. In the millions of years since they evolved, sulfur-oxidizing bacteria have adopted several highly successful strategies; some are ecological "specialists," and some are "generalists," but which genetic features underpin these ecological strategies are not well understood. We discovered a gene family that has become expanded in those species that also seem to be "generalists," revealing that duplication, repurposing, and reshuffling existing genes can be a powerful mechanism driving ecological lifestyle shifts.

Genome-based taxonomic classification of the genus Sulfitobacter along with the proposal of a new genus Parasulfitobacter gen. nov. and exploring the gene clusters associated with sulfur oxidation

BackgroundThe genus Sulfitobacter, a member of the family Roseobacteraceae, is widely distributed in the ocean and is believed to play crucial roles in the global sulfur cycle. However, gene clusters associated with sulfur oxidation in genomes of the type strains of this genus have been poorly studied. Furthermore, taxonomic errors have been identified in this genus, potentially leading to significant confusion in ecological and evolutionary interpretations in subsequent studies of the genus Sulfitobacter. This study aims to investigate the taxonomic status of this genus and explore the metabolism associated with sulfur oxidation.ResultsThis study suggests that Sulfitobacter algicola does not belong to Sulfitobacter and should be reclassified into a novel genus, for which we propose the name Parasulfitobacter gen. nov., with Parasulfitobacter algicola comb. nov. as the type species. Additionally, enzymes involved in the sulfur oxidation process, such as the sulfur oxidization (Sox) system, the disulfide reductase protein family, and the sulfite dehydrogenase (SoeABC), were identified in almost all Sulfitobacter species. This finding implies that the majority of Sulfitobacter species can oxidize reduced sulfur compounds. Differences in the modular organization of sox gene clusters among Sulfitobacter species were identified, along with the presence of five genes with unknown function located in some of the sox gene clusters. Lastly, this study revealed the presence of the demethylation pathway and the cleavage pathway used by many Sulfitobacter species to degrade dimethylsulfoniopropionate (DMSP). These pathways enable these bacteria to utilize DMSP as important source of sulfur and carbon or as a defence strategy.ConclusionsOur findings contribute to interpreting the mechanism by which Sulfitobacter species participate in the global sulfur cycle. The taxonomic rearrangement of S. algicola into the novel genus Parasulfitobacter will prevent confusion in ecological and evolutionary interpretations in future studies of the genus Sulfitobacter.

The impact of reduced sulfur compounds on aerobic granular sludge formation and biological phosphorus removal

Biological sulfur conversion combined with phosphorus removal represents an innovative biotechnology for activated sludge (AS). However, its effect on the formation of aerobic granular sludge (AGS) remains unclear. This study aimed at determining the impact of sulfide and thiosulfate on the performance of enhanced biological phosphorus removal (EBPR) and on AGS formation. Using two lab-scale sequencing batch reactors (SBR), we compared EBPR performance, the degree of granulation, and the enriched microbial community with sulfide (SBR-S, 20 mg S/L) or thiosulfate (SBR-T, 140 mg S/L) as primary sulfur source. Results indicate that both reactors achieved comparable EBPR performance, with a phosphorus removal rate of 98% in SBR-T and 99% in SBR-S. SBR-T resulted in compact granules with fast settling properties, while SBR-S resulted in dense floccular sludge, referred to as “densified sludge”. Both systems enriched a comparable microbial community with shared dominant genera, including Ca. Competibacter, Thiothrix, Ca. Accumulibacter and Dechloromonas. The higher abundance of Thiothrix unzii throughout the operating time in SBR-T, reaching 19.4%, is believed to have enhanced the granulation process. This study provides important insight into the role of reduced sulfur compounds in sludge densification and EBPR performance, relevant to sulfur-rich wastewaters such as those from industrial sources.

Graphene-decorated novel Z-scheme Bi@MOF composites promote high performance photocatalytic desulfurization

The Z-scheme photocatalyst constructed based on bismuth-based metal oxides (BMO) and metal–organic frameworks (MOF) holds significant potential for effectively degrading odorous Reduced Sulfur Compounds (RSC) due to its robust redox capabilities. However, challenges such as lattice mismatch, interface defects, and rapid recombination of photogenerated charges substantially impede the Z- scheme charge transfer in BMO@MOF photocatalysts. In this research, graphene was introduced into the BiVO4@NH2-UiO-66 system as an electron bridge and co-catalyst to reduce the interfacial transfer resistance and increase the absorption of near-infrared light, resulting in superior degradability of RSCs compared to both the individual components and BiVO4@NH2-UiO-66. The incorporated graphene not only serves as the growth substrate for BiVO4 and NH2-UiO-66 but also plays a crucial role as an electron mediator in enhancing the vectorial charge transfer from BiVO4 to NH2-UiO-66. This strengthens the Z-scheme charge transfer pathway, suppressing bulk charge recombination, increasing overall carrier density, and maintaining robust redox capabilities. Additionally, the investigation of active species and key intermediate products was conducted to explore potential degradation pathways of RSCs. This work demonstrates a novel approach in promoting photocatalytic degradation of RSCs by harnessing the synergistic effects between doping and heterogeneous structures within the photocatalyst.

The Oddy Test and the Photographic Activity Test (PAT): A Direct Comparison of Accelerated Aging Test Methods for Assessing Storage, Display, and Transport Materials

ABSTRACT Two accelerated aging tests, the Oddy test and the Photographic Activity Test (PAT), are used to predict the safety of storage, display, or transport materials used near cultural heritage objects. Despite being designed to predict possible chemical damage for metallic and photographic objects, respectively, results from both tests are often applied toward other collection types. A direct comparison between the two tests was completed by evaluating the same set of thirty-five materials. Results indicated very little correlation between the tests, both when comparing overall results as well as on the level of individual detector responses. An additional comparison with the lead acetate test (LAT), a selective test for reduced sulfur compounds, provided further evidence that while the Oddy and PAT are reliable at predicting the effect of volatile gases on metals or reactions with materials in direct contact with photographs, respectively, they are responding to reactive species differently. The Oddy test and PAT are selective and sensitive, but each to different species and concentrations of reactive chemicals. The tests are most effective when applied toward the object types each was intended to mimic, and results from the two tests should neither be equated nor applied globally toward all collection types.

Sulfur assimilation using gaseous carbonyl sulfide by the soil fungus Trichoderma harzianum.

Fungi have the capacity to assimilate a diverse range of both inorganic and organic sulfur compounds. It has been recognized that all sulfur sources taken up by fungi are in soluble forms. In this study, we present evidence that fungi can utilize gaseous carbonyl sulfide (COS) for the assimilation of a sulfur compound. We found that the filamentous fungus Trichoderma harzianum strain THIF08, which has constitutively high COS-degrading activity, was able to grow with COS as the sole sulfur source. Cultivation with 34S-labeled COS revealed that sulfur atom from COS was incorporated into intracellular metabolites such as glutathione and ergothioneine. COS degradation by strain THIF08, in which as much of the moisture derived from the agar medium as possible was removed, indicated that gaseous COS was taken up directly into the cell. Escherichia coli transformed with a COS hydrolase (COSase) gene, which is clade D of the β-class carbonic anhydrase subfamily enzyme with high specificity for COS but low activity for CO2 hydration, showed that the COSase is involved in COS assimilation. Comparison of sulfur metabolites of strain THIF08 revealed a higher relative abundance of reduced sulfur compounds under the COS-supplemented condition than the sulfate-supplemented condition, suggesting that sulfur assimilation is more energetically efficient with COS than with sulfate because there is no redox change of sulfur. Phylogenetic analysis of the genes encoding COSase, which are distributed in a wide range of fungal taxa, suggests that the common ancestor of Ascomycota, Basidiomycota, and Mucoromycota acquired COSase at about 790-670 Ma.IMPORTANCEThe biological assimilation of gaseous CO2 and N2 involves essential processes known as carbon fixation and nitrogen fixation, respectively. In this study, we found that the fungus Trichoderma harzianum strain THIF08 can grow with gaseous carbonyl sulfide (COS), the most abundant and ubiquitous gaseous sulfur compound, as a sulfur source. When the fungus grew in these conditions, COS was assimilated into sulfur metabolites, and the key enzyme of this assimilation process is COS hydrolase (COSase), which specifically degrades COS. Moreover, the pathway was more energy efficient than the typical sulfate assimilation pathway. COSase genes are widely distributed in Ascomycota, Basidiomycota, and Mucoromycota and also occur in some Chytridiomycota, indicating that COS assimilation is widespread in fungi. Phylogenetic analysis of these genes revealed that the acquisition of COSase in filamentous fungi was estimated to have occurred at about 790-670 Ma, around the time that filamentous fungi transitioned to a terrestrial environment.

Reduced sulfur compounds in the bottom sediments of meromictic lakes

This paper presents data on the content of reduced sulfur compounds in the bottom sediments of two meromictic reservoirs: Mogilnoe Lake (Barents Sea) and Lake Trekhtsvetnoe (White Sea). A distinctive feature of both reservoirs is the high content of hydrogen sulfide in the anaerobic monimolimnion. The total content of reduced sulfur compounds, characterized by the ƩSH2S parameter, averaged 0.500% for Mogilnoe Lake and 0.994% for Lake Trekhtsvetnoe. The main form of sulfur for both lakes was pyrite (more than 60% for Mogilnoe Lake and up to 80% for Lake Trekhtsvetnoe). Significant amounts of sulfur associated with organic matter were noted in the surface layers. The contents of acid-soluble monosulfides and elemental sulfur were not significantly different (no more than 10% of ƩSH2S). This distribution of forms in the composition of ƩSH2S makes the bottom sediments of the studied lakes similar to sea sediments. The high level of accumulation of reduced sulfur compounds in sediments is due to their provision of a sufficient amount of organic matter, which comes mainly from the chemocline zone.

Advance in the sulfur-based electron donor autotrophic denitrification for nitrate nitrogen removal from wastewater.

In the field of wastewater treatment, nitrate nitrogen (NO3--N) is one of the significant contaminants of concern. Sulfur autotrophic denitrification technology, which uses a variety of sulfur-based electron donors to reduce NO3--N to nitrogen (N2) through sulfur autotrophic denitrification bacteria, has emerged as a novel nitrogen removal technology to replace heterotrophic denitrification in the field of wastewater treatment due to its low cost, environmental friendliness, and high nitrogen removal efficiency. This paper reviews the advance of reduced sulfur compounds (such as elemental sulfur, sulfide, and thiosulfate) and iron sulfides (such as ferrous sulfide, pyrrhotite, and pyrite) electron donors for treating NO3--N in wastewater by sulfur autotrophic denitrification technology, including the dominant bacteria types and the sulfur autotrophic denitrification process based on various electron donors are introduced in detail, and their operating costs, nitrogen removal performance and impacts on the ecological environment are analyzed and compared. Moreover, the engineering applications of sulfur-based electron donor autotrophic denitrification technology were comprehensively summarized. According to the literature review, the focus of future industry research were discussed from several aspects as well, which would provide ideas for the application and optimization of the sulfur autotrophic denitrification process for deep and efficient removal of NO3--N in wastewater.

Heterotrophic bacteria dominate the sulfide oxidation process in coastal sediments

Sulfate reduction and sulfur oxidation are very active in coastal sediments. Together they shape the biogeochemistry and microbial ecology at hot places of organic matter metabolism. Compared to the well-studied sulfate reduction process, sulfur oxidation process is relatively lack of investigation. For a long time, autotrophic/mixotrophic bacteria were thought to be the main sulfur oxidation strains in sediments. Herein, we investigated the distribution of reduced sulfur compounds in differently layers of coastal sediments at the Yellow sea. We found that sulfide (H2S), sulfane sulfur (S0), and thiosulfate mainly accumulated in deep anaerobic sediments and were mostly oxidized in surface sediments (∼3 cm in depth). Bacterial community analysis indicated that heterotrophic bacteria were dominating species in surface sediments. Metatranscriptome analysis showed that transcripts of flavocytochrome c sulfide dehydrogenase (FCC), persufide dioxygenase (PDO), and sulfite-oxidizing enzyme (SOE) were abundant in surface sediments. In addition, using a Roseobacterium (Ruegeria pomeroyi DSS-3) as the model strain, we investigated how FCC, PDO, and SOE work together to oxidize H2S to sulfate. This study clarified that heterotrophic bacteria are the main sulfur oxidation strains in coastal sediments.

Drifting in the deep: Metatranscriptomics and metabarcoding reveal sustained metabolic activity and community composition in hydrothermal vent plume microbial communities

The deep sea is the largest habitat on our planet, supporting a vast diversity of organisms which have yet to be fully described. This habitat is punctuated by hydrothermal vents in which energy derived from chemosynthesis drives carbon fixation, supporting a complex and rich food web. Connectivity between vent systems remains an active area of research, with questions as to how vent-influenced microbial function and diversity persists over space and time. In particular, the role hydrothermal vent plumes play as potential highways for connectivity and biogeography is not well understood. To add to the growing body of research, this study sampled plume waters above the Moytirra hydrothermal vent field, located just north of the Azores. We examined how hydrothermal vent plume community biodiversity and metabolic activities change with distance from the vent using a combination of metabarcoding and metatranscriptomic sequencing. We detected a rich diversity of both prokaryotic and eukaryotic organisms inhabiting the plume, which remained metabolically active for kilometers from the vent source. Enriched sulfur metabolism functional signals and relative abundance of sulfur oxidizing bacteria suggest reduced sulfur compounds are a fundamental energy source within plume waters. Additionally, we observed evidence of top-down controls on primary production through both known grazers and putative viral activity. Although community-level functional signals suggest active metabolic functions for over a kilometer north or south of the vent field, these functions grew increasingly dissimilar to those observed directly above the vent site, and bacterial communities displayed indications of entering quiescent stages, likely due to decreasing resources and reduced temperatures. These data provide a first glimpse of Moytirra’s microbial biodiversity, in addition to providing a high-resolution understanding of life on the drift within a hydrothermal plume, its persistence with distance, and implications for connectivity.

Physiological and Genomic Characterization of a Novel Obligately Chemolithoautotrophic, Sulfur-Oxidizing Bacterium of Genus Thiomicrorhabdus Isolated from a Coastal Sediment.

Thiomicrorhabdus species, belonging to the family Piscirickettsiaceae in the phylum Pseudomonadotav are usually detected in various sulfur-rich marine environments. However, only a few bacteria of Thiomicrorhabdus have been isolated, and their ecological roles and environmental adaptations still require further understanding. Here, we report a novel strain, XGS-01T, isolated from a coastal sediment, which belongs to genus Thiomicrorhabdus and is most closely related to Thiomicrorhabdus hydrogeniphila MAS2T, with a sequence similarity of 97.8%. Phenotypic characterization showed that XGS-01T is a mesophilic, sulfur-oxidizing, obligate chemolithoautotrophy, with carbon dioxide as its sole carbon source and oxygen as its sole electron acceptor. During thiosulfate oxidation, strain XGS-01T can produce extracellular sulfur of elemental α-S8, as confirmed via scanning electron microscopy and Raman spectromicroscopy. Polyphasic taxonomy results indicate that strain XGS-01T represents a novel species of the genus Thiomicrorhabdus, named Thiomicrorhabdus lithotrophica sp. nov. Genomic analysis confirmed that XGS-01T performed thiosulfate oxidation through a sox multienzyme complex, and harbored fcc and sqr genes for sulfide oxidation. Comparative genomics analysis among five available genomes from Thiomicrorhabdus species revealed that carbon fixation via the oxidation of reduced-sulfur compounds coupled with oxygen reduction is conserved metabolic pathways among members of genus Thiomicrorhabdus.

Reduced Sulfur Compounds in Bottom Sediments of Lakes at Different Stages of Separation from Kandalaksha Bay of the White Sea (Meromictic Lake Trekhtsvetnoe)

Reduced Sulfur Compounds in Bottom Sediments of Lakes at Different Stages of Separation from Kandalaksha Bay of the White Sea (Meromictic Lake Trekhtsvetnoe)