ChAP 1.0: a stationary tropospheric sulfur cycle for Earth system models of intermediate complexity

A stationary, computationally efficient scheme ChAP 1.0 (Chemical and Aerosol Processes, version 1.0) for the sulfur cycle in the troposphere is developed. This scheme is designed for Earth system models of intermediate complexity (EMICs). The scheme accounts for sulfur dioxide emissions into the atmosphere, its deposition to the surface, oxidation to sulfates, and dry and wet deposition of sulfates on the surface. The calculations with the scheme are forced by anthropogenic emissions of sulfur dioxide into the atmosphere for 1850–2000 adopted from the CMIP5 dataset and by the ERA-Interim meteorology assuming that natural sources of sulfur into the atmosphere remain unchanged during this period. The ChAP output is compared to changes of the tropospheric sulfur cycle simulations with the CMIP5 data, with the IPCC TAR ensemble, and with the ACCMIP phase II simulations. In addition, in regions of strong anthropogenic sulfur pollution, ChAP results are compared to other data, such as the CAMS reanalysis, EMEP MSC-W, and individual model simulations. Our model reasonably reproduces characteristics of the tropospheric sulfur cycle known from these information sources. In our scheme, about half of the emitted sulfur dioxide is deposited to the surface, and the rest is oxidised into sulfates. In turn, sulfates are mostly removed from the atmosphere by wet deposition. The lifetimes of the sulfur dioxide and sulfates in the atmosphere are close to 1 and 5 d, respectively. The limitations of the scheme are acknowledged, and the prospects for future development are figured out. Despite its simplicity, ChAP may be successfully used to simulate anthropogenic sulfur pollution in the atmosphere at coarse spatial scales and timescales.

Composition And Key-Influencing Factors of Bacterial Communities Active In Sulfur Cycling of Soda Lake Sediments

Bacteria are important participants in sulfur cycle of the extremely haloalkaline environment, e.g. soda lakes. The effects of physicochemical factors on the composition of sulfide-oxidizing bacteria (SOB) and sulfate-reducing bacteria (SRB) in soda lakes have remained elusive. Here, we surveyed the communities structure of total bacteria, SOB and SRB based on 16S rRNA, soxB and dsrB gene sequencing, respectively, in five soda lakes with different physicochemical factors. The results showed that the dominant bacteria in soda lakes sediments belonged to the phyla Proteobacteria, Bacteroidetes, Halanaerobiaeota, Firmicutes and Actinobacteria. SOB and SRB were widely distributed in lakes with different physicochemical characteristics，and the community composition were different . In general, salinity and inorganic nitrogen sources (NH4+-N, NO3--N) were the most significant factors. Specifically, the communities of SOB, mainly including Thioalkalivibrio, Burkholderia, Paracoccus, Bradyrhizobium, and Hydrogenophaga genera, were remarkably influenced by the levels of NH4+-N and salinity. Yet, for SRB communities, including Desulfurivibrio, Candidatus Electrothrix, Desulfonatronospira, Desulfonatronum, Desulfonatronovibrio, Desulfonatronobacter and so on, the most significant determinants were salinity and NO3--N. Besides, Rhodoplanes played a significant role in the interaction between SOB and SRB. From our results, the knowledge regarding the community structures of SOB and SRB in extremely haloalkaline environment was extended.

Stimulation of Dissimilatory Sulfate Reduction in Response to Sulfate in Microcosm Incubations from Two Contrasting Temperate Peatlands near Ithaca, NY, USA

Peatlands are responsible for over half of wetland methane emissions, yet major uncertainties remain regarding carbon flow, especially when increased availability of electron acceptors stimulate competing physiologies. We used microcosm incubations to study the effects of sulfate on microorganisms in two temperate peatlands, one bog and one fen. Three different electron donor treatments were used (13C-acetate, 13C-formate, and a mixture of 12C short-chain fatty acids) to elucidate the responses of sulfate-reducing bacteria (SRB) and methanogens to sulfate stimulation. Methane production was measured and metagenomic sequencing was performed, with only the heavy DNA fraction sequenced from treatments receiving 13C electron donors. Our data demonstrate stimulation of dissimilatory sulfate reduction in both sites, with contrasting community responses. In McLean Bog (MB), hydrogenotrophic Deltaproteobacteria and acetotrophic Peptococcaceae lineages of SRB were stimulated, as were lineages with unclassified dissimilatory sulfite reductases. In Michigan Hollow Fen (MHF), there was little stimulation of Peptococcaceae populations, and a small stimulation of Deltaproteobacteria SRB populations only in the presence of formate as electron donor. Sulfate stimulated an increase in relative abundance of reads for both oxidative and reductive sulfite reductases, suggesting stimulation of an internal sulfur cycle. Together, these data indicate a stimulation of SRB activity in response to sulfate in both sites, with a stronger growth response in MB than MHF. This study provides valuable insights into microbial community responses to sulfate in temperate peatlands and is an important first step to understanding how SRB and methanogens compete to regulate carbon flow in these systems.

Cysteinolic Acid Is a Widely Distributed Compatible Solute of Marine Microalgae

Phytoplankton rely on bioactive zwitterionic and highly polar small metabolites with osmoregulatory properties to compensate changes in the salinity of the surrounding seawater. Dimethylsulfoniopropionate (DMSP) is a main representative of this class of metabolites. Salinity-dependent DMSP biosynthesis and turnover contribute significantly to the global sulfur cycle. Using advanced chromatographic and mass spectrometric techniques that enable the detection of highly polar metabolites, we identified cysteinolic acid as an additional widely distributed polar metabolite in phytoplankton. Cysteinolic acid belongs to the class of marine sulfonates, metabolites that are commonly produced by algae and consumed by bacteria. It was detected in all dinoflagellates, haptophytes, diatoms and prymnesiophytes that were surveyed. We quantified the metabolite in different phytoplankton taxa and revealed that the cellular content can reach even higher concentrations than the ubiquitous DMSP. The cysteinolic acid concentration in the cells of the diatom Thalassiosira weissflogii increases significantly when grown in a medium with elevated salinity. In contrast to the compatible solute ectoine, cysteinolic acid is also found in high concentrations in axenic algae, indicating biosynthesis by the algae and not the associated bacteria. Therefore, we add this metabolite to the family of highly polar metabolites with osmoregulatory characteristics produced by phytoplankton.

Novel Insights into Dimethylsulfoniopropionate Catabolism by Cultivable Bacteria in the Arctic Kongsfjorden

Dimethylsulfoniopropionate (DMSP) is one of the most abundant organic sulfur compounds in the oceans, which is mainly degraded by bacteria through two pathways, a cleavage pathway and a demethylation pathway. Its volatile catabolites dimethyl sulfide (DMS) and methanethiol (MT) in these pathways play important roles in the global sulfur cycle and have potential influences on the global climate. Intense DMS/DMSP cycling occurs in the Arctic. However, little is known about the diversity of cultivable DMSP-catabolizing bacteria in the Arctic and how they catabolize DMSP. Here, we screened DMSP-catabolizing bacteria from Arctic samples and found that bacteria of four genera ( Psychrobacter , Pseudoalteromonas , Alteromonas and Vibrio ) could grow with DMSP as the sole carbon source, among which Psychrobacter and Pseudoalteromonas are predominant. Four representative strains ( Psychrobacter sp. K31L, Pseudoalteromonas sp. K222D, Alteromonas sp. K632G and Vibrio sp. G41H) from different genera were selected to probe their DMSP catabolic pathways. All these strains produce DMS and MT simultaneously during their growth on DMSP, indicating that all strains likely possess the two DMSP catabolic pathways. On the basis of genomic and biochemical analyses, the DMSP catabolic pathways in these strains were proposed. Bioinformatic analysis indicated that most bacteria of Psychrobacter and Vibrio have the potential to catabolize DMSP via the demethylation pathway, and that only a small portion of Psychrobacter strains may catabolize DMSP via the cleavage pathway. This study provides novel insights into DMSP catabolism in marine bacteria. IMPORTANCE Dimethylsulfoniopropionate (DMSP) is abundant in the oceans. The catabolism of DMSP is an important step of the global sulfur cycle. Although Gammaproteobacteria are widespread in the oceans, the contribution of Gammaproteobacteria in global DMSP catabolism is not fully understood. Here, we found that bacteria of four genera belonging to Gammaproteobacteria ( Psychrobacter , Pseudoalteromonas , Alteromonas and Vibrio ), which were isolated from Arctic samples, were able to grow on DMSP. The DMSP catabolic pathways of representative strains were proposed. Bioinformatic analysis indicates that most bacteria of Psychrobacter and Vibrio have the potential to catabolize DMSP via the demethylation pathway, and that only a small portion of Psychrobacter strains may catabolize DMSP via the cleavage pathway. Our results suggest that novel DMSP dethiomethylases/demethylases may exist in Pseudoalteromonas , Alteromonas and Vibrio , and that Gammaproteobacteria may be important participants in marine, especially in polar DMSP cycling.

Microbial Communities Involved in Methane, Sulfur, and Nitrogen Cycling in the Sediments of the Barents Sea

A combination of physicochemical and radiotracer analysis, high-throughput sequencing of the 16S rRNA, and particulate methane monooxygenase subunit A (pmoA) genes was used to link a microbial community profile with methane, sulfur, and nitrogen cycling processes. The objects of study were surface sediments sampled at five stations in the northern part of the Barents Sea. The methane content in the upper layers (0–5 cm) ranged from 0.2 to 2.4 µM and increased with depth (16–19 cm) to 9.5 µM. The rate of methane oxidation in the oxic upper layers varied from 2 to 23 nmol CH4 L−1 day−1 and decreased to 0.3 nmol L−1 day−1 in the anoxic zone at a depth of 16–19 cm. Sulfate reduction rates were much higher, from 0.3 to 2.8 µmol L −1 day −1. In the surface sediments, ammonia-oxidizing Nitrosopumilaceae were abundant; the subsequent oxidation of nitrite to nitrate can be carried out by Nitrospira sp. Aerobic methane oxidation could be performed by uncultured deep-sea cluster 3 of gamma-proteobacterial methanotrophs. Undetectable low levels of methanogenesis were consistent with a near complete absence of methanogens. Anaerobic methane oxidation in the deeper sediments was likely performed by ANME-2a-2b and ANME-2c archaea in consortium with sulfate-reducing Desulfobacterota. Sulfide can be oxidized by nitrate-reducing Sulfurovum sp. Thus, the sulfur cycle was linked with the anaerobic oxidation of methane and the nitrogen cycle, which included the oxidation of ammonium to nitrate in the oxic zone and denitrification coupled to the oxidation of sulfide in the deeper sediments. Methane concentrations and rates of microbial biogeochemical processes in sediments in the northern part of the Barents Sea were noticeably higher than in oligotrophic areas of the Arctic Ocean, indicating that an increase in methane concentration significantly activates microbial processes.

L-Cysteine Synthase Enhanced Sulfide Biotransformation in Subtropical Marine Mangrove Sediments as Revealed by Metagenomics Analysis

High sulfides concentrations can be poisonous to environment because of anthropogenic waste production or natural occurrences. How to elucidate the biological transformation mechanisms of sulfide pollutants in the subtropical marine mangrove ecosystem has gained increased interest. Thus, in the present study, the sulfide biotransformation in subtropical mangroves ecosystem was accurately evaluated using metagenomic sequencing and quantitative polymerase chain reaction analysis. Most abundant genes were related to the organic sulfur transformation. Furthermore, an ecological model of sulfide conversion was constructed. Total phosphorus was the dominant environmental factor that drove the sulfur cycle and microbial communities. We compared mangrove and non-mangrove soils and found that the former enhanced metabolism that was related to sulfate reduction when compared to the latter. Total organic carbon, total organic nitrogen, iron, and available sulfur were the key environmental factors that effectively influenced the dissimilatory sulfate reduction. The taxonomic assignment of dissimilatory sulfate-reducing genes revealed that Desulfobacterales and Chromatiales were mainly responsible for sulfate reduction. Chromatiales were most sensitive to environmental factors. The high abundance of cysE and cysK could contribute to the coping of the microbial community with the toxic sulfide produced by Desulfobacterales. Collectively, these findings provided a theoretical basis for the mechanism of the sulfur cycle in subtropical mangrove ecosystems.

Microbial Communities of the Hydrothermal Scaly-Foot Snails From Kairei and Longqi Vent Fields

The microbial communities of the hydrothermal Scaly-foot Snails (SFSs) from independent hydrothermal vent fields have not been investigated in depth. In this study, we collected SFSs from two different hydrothermal environments located on the Central Indian Ridge (CIR) and the Southwest Indian Ridge (SWIR), the Kairei and Longqi vent fields, respectively. Additionally, one SFS collected from the Kairei vent field was reared for 16 days with in situ deep-sea seawater. The epibiotic and internal samples of SFSs, including ctenidium, esophageal gland, visceral mass, shells, and scales, were examined for microbial community compositions based on the 16S rRNA gene. Our results revealed significant differences in microbial community composition between SFSs samples collected from Kairei and Longqi vent fields. Moreover, the microbial communities of epibiotic and internal SFS samples also exhibited significant differences. Epibiotic SFS samples were dominated by the bacterial lineages of Sulfurovaceae, Desulfobulbaceae, Flavobacteriaceae, and Campylobacteraceae. While in the internal SFS samples, the genus Candidatus Thiobios, affiliated with the Chromatiaceae, was the most dominant bacterial lineage. Furthermore, the core microbial communities of all samples, which accounted for 78 ∼ 92% of sequences, were dominated by Chromatiaceae (27 ∼ 49%), Sulfurovaceae (10 ∼ 35%), Desulfobulbaceae (2 ∼ 7%), and Flavobacteriaceae (3 ∼ 7%) at the family level. Based on the results of random forest analysis, we also found the genera Desulfobulbus and Sulfurovum were the primary bacterial lineages responsible for the dissimilarity of microbial communities between the SFS samples collected from the Kairei and Longqi vent fields. Our results indicated that the microbial lineages involved in the sulfur cycle were the key microorganisms, playing a crucial role in the hydrothermal vent ecosystems. Our findings expand current knowledge on microbial diversity and composition in the epibiotic and internal microbial communities of SFS collected from different hydrothermal vent fields.