Sulfur Cycle Bacteria Research Articles

Increased oxygen partial pressure enhances toxicity reduction by membrane aerated biofilm reactor treating oil and gas industrial wastewater

Wastewater produced during oil and gas extraction processes is one of the largest residual water streams. Also known as produced water (PW), it has a complex composition and is typically toxic to aquatic ecosystems. This study explores the use of membrane aerated biofilm reactors (MABR) for biological removal of dissolved organic compounds and associated toxicity. Three different oxygen partial pressures (0.2, 0.6 and 1 bar), the last two mimicking subsea pressures at 20 and 40 m below the sea level, respectively, were tested at three different hydraulic retention times (HRT of 24, 12 and 6 h). Reactors were fed both with onshore and offshore PW. Removal rates for organic carbon increased at decreasing HRT. Highest oxygen partial pressure led to best performance at 6 h HRT (30.1 ± 3.0 g-COD m−2 d−1) when treating onshore PW and at all HRT when treating offshore PW, with highest COD removal rate still at 6 h HRT (9.4 ± 1 g-COD m−2 d−1). Removal efficiencies ranged from 78 % when treating onshore PW at 24 h HRT to 36–49 % when treating offshore PW at 6 h HRT. All treatments led to a reduction in toxicity (>92 % reduction for offshore PW), with 0.2 bar oxygen partial pressure showing worst performance, while 0.6 and 1 bar did not show significant differences. The biofilms were dominated by hydrocarbonoclastic, responsible of hydrocarbons biodegradation, and sulfur cycling bacteria. Overall, MABR were effective treating PW and operating at higher oxygen partial pressures yield to better performance, especially at high volumetric loading rates.

The impact of stone position and location on the microbiome of a marble statue

Microbial proliferation and biodeterioration constitutes a serious threat towards the preservation of stone monuments and relics. Geometry and exposure have been recently pinpointed as important factors determining the microbiome organization in stone monuments. In this work, the impacts of position and location on the microbial communities and their predicted metabolical and ecological profiles on a marble statue were studied. We sampled various epilithic stone biofilms from the Brotero statue (Coimbra’s UNESCO World Heritage site) and studied them by Next-generation Sequencing of the V3/V4 and the ITS2 regions, and bioinformatic analyses. We verified that statue location/heights have a more relevant impact than position/sides on the microbiome, and that Fungal and Chlorophyta communities showed a more diverse and less stable structural organization than Bacteria. Thus, while sub-aerial biofilms were mainly colonized by selective groups of extremophilic microorganisms, our results highlight that this specificity is more pronounced in prokaryotes. Bacterial metabolic functional distribution patterns were found to be distinct and adapted according to statue heights, while fungi displayed a strong domination of various types of saprotrophs. In addition to various “degraders” present in all samples, lower statue areas displayed strong connections with nitrogen fixators, while high and middle zones displayed stronger correlations with nitrogen and sulfur cycle bacteria. Moreover, biodeterioration at these sites can be promoted by biodeteriogenic cyanobacteria, bacteria linked to biogeochemical cycles, microcolonial Fungi and Chlorophyta able to thrive under hostile environments. In addition, mutualistic and competitive relationships between taxonomic groups were detected, that will require additional focus on future studies.

Electrostatic self-assembled nickel cobalt sulfide/Ti3C2 Mxene as a bio-capacitive anode for specific attracting sulfur-cycling bacteria and regulating extracellular electron transfer efficiency

Microbial fuel cells have been proposed as one of the sustainable and potential technologies for treating contaminants and synchronously producing green energy. However, the poor performance of the anode is a major obstacle in the practical application of MFCs. To address this challenge, the rational design of anode materials with enhanced biocatalytic and biocompatible properties has been considered as an effective approach to improve extracellular electron transfer (EET) processes and general MFC performance. Herein, in light of the interaction between the transition metal and exoelectrogens, nickel-cobalt sulfide/Ti3C2 Mxene (NiCo2S4/Mxene) is prepared by electrostatic assembly, which combined positively charged sea-urchin-like NiCo2S4 with negatively charged Mxene. This not only prevents the stacking of NiCo2S4 and Mxene but also accelerates the EET process by harnessing their biocompatibility and biocatalyst. As expected, the MFC with NiCo2S4/Mxene harvested higher electricity energy (9.66 ± 0.28 W/m3), significantly exceeded those of plain carbon felt (CF, 1.68 ± 0.13 W/m3), Mxene (4.32 ± 0.20 W/m3) and NiCo2S4 (5.41 ± 0.22 W/m3). Moreover, the microbial community analysis further revealed that the sulfide composite attracts a higher percentage of sulfur-cycling exoelectrogens (Desulfuromonas (24.25%) and Marinobacterium (15.75%)), motivating associated metabolic pathways with more efficient electricity generation processes. Such commendable performances are mainly attributed to the synergistic effect between NiCo2S4 and Mxene, which confers the bioanode with good biocompatibility and biocatalyst for biofilm adhesion and colonization, as well as providing abundant transition metals and sulfide active sites for the EET process. Our finding provides a facile routine for developing sulfide with appropriate modification as anode material for favorable performance of MFC, providing insights for sustainable and cleaner energy production in the future.

Inoculation with plant growth-promoting rhizobacteria improves seagrass Thalassia hemprichii photosynthesis performance and shifts rhizosphere microbiome

Plant growth-promoting rhizobacteria (PGPR) inoculation is a crucial strategy for maintaining the sustainability of agriculture and presents a promising solution for seagrass ecological restoration in the face of disturbances. However, the possible roles and functions of PGPRs in the seagrass rhizosphere remain unclear. Here, we isolated rhizosphere bacterial strains from both reef and coastal regions and screened two PGPR isolates regarding their in vivo functional traits. Subsequently, we conducted microcosm experiments to elucidate how PGPR inoculation affected seagrass photosynthesis and shape within each rhizosphere microbiome. Both screened PGPR strains, Raoultella terrigena NXT28 and Bacillus aryabhattai XT37, excelled at expressing a specific subset of plant-beneficial functions and increased the photosynthetic rates of the seagrass host. PGPR inoculation not only decreased the abundance of sulfur-cycling bacteria, it also improved the abundance of putative iron-cycling bacteria in the seagrass rhizosphere. Strain XT37 successfully colonized the seagrass rhizosphere and displayed a leading role in microbial network structure. As a nitrogen-fixing bacteria, NXT28 showed potential to change the microbial nitrogen cycle with denitrification in the rhizosphere and alter dissimilatory and assimilatory nitrate reduction in bulk sediment. These findings have implications for the development of eco-friendly strategies aimed at exploiting microbial communities to confer sulfide tolerance in coastal seagrass ecosystem.

Diversity at single nucleotide to pangenome scales among sulfur cycling bacteria in salt marshes.

Salt marshes are known for their significant carbon storage capacity, and sulfur cycling is closely linked with the ecosystem-scale carbon cycling in these ecosystems. Sulfate reducers are key for the decomposition of organic matter, and sulfur oxidizers remove toxic sulfide, supporting the productivity of marsh plants. To date, the complexity of coastal environments, heterogeneity of the rhizosphere, high microbial diversity, and uncultured majority hindered our understanding of the genomic diversity of sulfur-cycling microbes in salt marshes. Here, we use comparative genomics to overcome these challenges and provide an in-depth characterization of sulfur-cycling microbial diversity in salt marshes. We characterize communities across distinct sites and plant species and uncover extensive genomic diversity at the taxon level and specific genomic features present in MAGs affiliated with uncultivated sulfur-cycling lineages. Our work provides insights into the partnerships in salt marshes and a roadmap for multiscale analyses of diversity in complex biological systems.

Seasonal coral-algae interactions drive White Mat Syndrome coral disease outbreaks

Ocean warming drives not only the increase of known coral disease prevalence but facilitates the emergence of new undescribed ones too. As climate change is restructuring coral ecosystems, novel biological interactions could lead to an increase in coral disease in both tropical and marginal coral communities. White Mat Syndrome (WMS) represents one such emerging coral disease, with outbreaks associated with high algal interactions and seasonal summer temperatures. However, the mechanisms behind its pathogenesis, modes of transmission and causative pathogens remain to be identified. Ex situ infection experiments pairing the coral Porites heronensis together with local potential contributory factors show that the macroalga Gelidium elegans hosts and proliferates the WMS microbial mat. This pathogenic consortium then infects adjacent corals, leading to their mortality. WMS was also observed to transmit following the fragmentation of the microbial mat, which was able to infect healthy corals. Sulfur-cycling bacteria (i.e., Beggiatoa, Desulfobacter sp., Arcobacteraceae species) and the free-living spirochete Oceanospirochaeta sediminicola were found consistently in both WMS and G. elegans consortia, suggesting they are putative pathogens of WMS. The predicted functional roles of these pathogenic consortia showed degradative processes, hinting that tissue lyses could drive mat formation and spread. Coral-algae interactions will rise due to ongoing ocean warming and coral ecosystem degradation, likely promoting the virulence and prevalence of algal-driven coral diseases.

Soil sulfur cycle bacteria and metabolites affected by soil depth and afforestation conditions in high-sulfur coal mining areas

This study aimed to clarify the changes in sulfur-driven microorganisms and sulfur metabolic pathways in the vertical soil profile during the restoration of different afforestation types. Soils of varying afforestation patterns (grassland, shrubland, woodland) in high‑sulfur coal mining areas (Gujiao City, China) were analysed to determine the characteristics of the sulfur distribution, microbial community structure, and sulfur metabolites in shallow (10 cm), middle (30 cm), and deep (50 cm) soils. Compared with the area without vegetation, the soil in the planted area had higher total soil S (5.1–58.6 %), Fe (37.5–67.4 %), and Cu (28.3–54.2 %); the content of these elements showed a consistent increase with depth. Afforestation resulted in increased pH by 0.8–1.3 pH units, organic carbon (1.6–2.9 times), total N (30.2–46.9 %), and available N (58.3–78.2 %) in the soil. Additionally, the electrical conductivity of the shallow soil in the three plant cover areas decreased by 78–82 %. The diversity of 16S bacterial showed that different afforestation types shaped the structure of specific microbial communities at different soil depths. Afforestation also showed a promotion of abundance of soil sulfur-related microorganisms (e.g., Desulfovibrio (0.8–34.2 %), Acidiferrobacter (0.3–32.8 %), Acidithiobacillus (1.2–21.7 %), and Thiomonas (0.6–15.6 %)). Plant cover induced the vertical spatial distribution pattern of sulfur metabolites in high-sulfur coal mines showing a shallow > middle > deep layer, and afforestation enhanced the transformation process of sulfur metabolites in shallow soil. The main metabolic pathways for soil sulfur metabolism involve sulfur-containing amino acids, such as cysteine and methionine metabolism, taurine, and hypotaurine. Interaction analysis indicated that Lysobacter, Luteimonas, and Leptospirillum made greater contributions to the changes in sulfur metabolites. The findings from this study suggest that the distribution of sulfur and soil properties in vertical depth soil of different afforestation types in high-sulfur coal mining areas recruit specific bacteria, which drive soil sulfur metabolic conversion and reestablishment of soil sulfur homeostasis, and the shallow layers of the soil were critical areas for turnover of sulfur metabolite. These results provide insights for understanding biochemical sulfur cycling in vertical soil depth under different afforestation models.

Temporal changes of bacterial and archaeal community structure and their corrosion mechanisms in flowback and produced water from shale gas well

Superficial research on flowback and produced (FP) water from shale gas wells limit the targeted practice of corrosion protection and wastewater treatment. This study analyzes the injected fluid and the FP water at different stages in a single shale gas well with freshwater hydraulic fracturing (HF) in the Changning Shale Gas Field located in the Sichuan Basin, China. The analysis includes water-quality parameters, corrosion electrochemical properties, as well as bacterial and archaeal community structure. The results show that changes occurred at different exploration stages to the main corrosion microorganisms in the FP water, including bacteria and archaea, and their corrosion mechanisms. In the flowback stage, the genera Pseudomonas, Caenispirillum, Proteiniphilum, and Methanothermobacter were the main corrosive microbiota, whereas sulfur-cycling bacteria such as Arcobacter, Marinobacterium, and Desulfuromonas played the main corrosive role during the production period. After two months of production, the genus Arcobacter was highly enriched in the produced water, which is an atypical sulfate-reducing bacteria genus, and the corrosion rate reached 0.2518 mm/a as determined by corrosion electrochemistry. This study characterized the corrosivity of FP water intuitively using electrochemical tests and broadened the horizons of the corrosion mechanism caused by microbial succession over the shale gas exploitation and production stages. It may provide novel guidance for the treatment of FP water for recycling and corrosion protection in shale gas production.

Sulfur Cycling as a Viable Metabolism under Simulated Noachian/Hesperian Chemistries.

Water present on the surface of early Mars (>3.0 Ga) may have been habitable. Characterising analogue environments and investigating the aspects of their microbiome best suited for growth under simulated martian chemical conditions is key to understanding potential habitability. Experiments were conducted to investigate the viability of microbes from a Mars analogue environment, Colour Peak Springs (Axel Heiberg Island, Canadian High Arctic), under simulated martian chemistries. The fluid was designed to emulate waters thought to be typical of the late Noachian, in combination with regolith simulant material based on two distinct martian geologies. These experiments were performed with a microbial community from Colour Peak Springs sediment. The impact on the microbes was assessed by cell counting and 16S rRNA gene amplicon sequencing. Changes in fluid chemistries were tested using ICP-OES. Both chemistries were shown to be habitable, with growth in both chemistries. Microbial communities exhibited distinct growth dynamics and taxonomic composition, comprised of sulfur-cycling bacteria, represented by either sulfate-reducing or sulfur-oxidising bacteria, and additional heterotrophic halophiles. Our data support the identification of Colour Peak Springs as an analogue for former martian environments, with a specific subsection of the biota able to survive under more accurate proxies for martian chemistries.

Sulfate-dependant microbially induced corrosion of mild steel in the deep sea: a 10-year microbiome study

BackgroundMetal corrosion in seawater has been extensively studied in surface and shallow waters. However, infrastructure is increasingly being installed in deep-sea environments, where extremes of temperature, salinity, and high hydrostatic pressure increase the costs and logistical challenges associated with monitoring corrosion. Moreover, there is currently only a rudimentary understanding of the role of microbially induced corrosion, which has rarely been studied in the deep-sea. We report here an integrative study of the biofilms growing on the surface of corroding mooring chain links that had been deployed for 10 years at ~2 km depth and developed a model of microbially induced corrosion based on flux-balance analysis.MethodsWe used optical emission spectrometry to analyze the chemical composition of the mooring chain and energy-dispersive X-ray spectrometry coupled with scanning electron microscopy to identify corrosion products and ultrastructural features. The taxonomic structure of the microbiome was determined using shotgun metagenomics and was confirmed by 16S amplicon analysis and quantitative PCR of the dsrB gene. The functional capacity was further analyzed by generating binned, genomic assemblies and performing flux-balance analysis on the metabolism of the dominant taxa.ResultsThe surface of the chain links showed intensive and localized corrosion with structural features typical of microbially induced corrosion. The microbiome on the links differed considerably from that of the surrounding sediment, suggesting selection for specific metal-corroding biofilms dominated by sulfur-cycling bacteria. The core metabolism of the microbiome was reconstructed to generate a mechanistic model that combines biotic and abiotic corrosion. Based on this metabolic model, we propose that sulfate reduction and sulfur disproportionation might play key roles in deep-sea corrosion.ConclusionsThe corrosion rate observed was higher than what could be expected from abiotic corrosion mechanisms under these environmental conditions. High corrosion rate and the form of corrosion (deep pitting) suggest that the corrosion of the chain links was driven by both abiotic and biotic processes. We posit that the corrosion is driven by deep-sea sulfur-cycling microorganisms which may gain energy by accelerating the reaction between metallic iron and elemental sulfur. The results of this field study provide important new insights on the ecophysiology of the corrosion process in the deep sea.

Effects of fish farm activities on the sponge Weberella bursa, and its associated microbiota

Sustained growth of world-wide sea farming and the search of optimal growing conditions have driven several countries, including Norway, to establish new finfish sites in more exposed, high current locations. Characterized by a range of gravel, broken rock and/or bedrock, these complex environments and the associated diverse range of epifauna species are not easily monitored via traditional methodologies (e.g. morpho-taxonomic identification and enumeration, and compound analyses of sediment grabs). Consequently, little is known about many of the benthic inhabitants, or how they may respond to fish farming. In this study, we aimed to initiate addressing this knowledge gap by assessing the response of the sponge Weberella bursa (Polymastidea) to salmon aquaculture. Fourteen specimens were translocated along a distance gradient from a salmon farm located along the mid-west coast of Norway. Following 7 months of exposure, their epithelial tissue were analysed for gene expression analysis (mRNA), fatty acid (FA), stable isotope and taxonomic and functional microbiome characterization. Among all datasets, only fatty acid profiles showed significant changes associated with fish farm activities, with higher proportion of terrestrial FAs and long saturated and monounsaturated FAs near the farm. These results suggest that W. bursa sponges may be more resistant to organic enrichment than previously thought. Nonetheless, several putative indicators of non-lethal response could be identified. Specifically, W. bursa specimens located underneath the farm tended to have reduced ribosomal activity while having increased expression of genes controlling cell apoptosis (e.g. caspase-3, cytochrome c oxidase and death domain proteins). Based on predictive functional analysis, specimens near to the farm were also found to be particularly enriched in sulfur and nitrogen cycling bacteria, and in microbial taxa with anti-toxin and xenobiotic biodegradation capability, notably of benzyl benzoate compounds used in sea lice treatments. These results indicate that potentially harmful elements such as sulfite, nitrite and pesticides may be neutralized and degraded by a particularly enriched set of bacteria in W. bursa microbiome. While additional research is needed to validate these putative indicators, our study provides a first glimpse as to how sessile organisms may respond and adapt to environmental changes induced by fin fish farming, and pave the way to the development of novel monitoring tools adapted to mix and hard bottom habitats.

The bacterial sulfur cycle in expanding dysoxic and euxinic marine waters.

Dysoxic marine waters (DMW, < 1 μM oxygen) are currently expanding in volume in the oceans, which has biogeochemical, ecological and societal consequences on a global scale. In these environments, distinct bacteria drive an active sulfur cycle, which has only recently been recognized for open‐ocean DMW. This review summarizes the current knowledge on these sulfur‐cycling bacteria. Critical bottlenecks and questions for future research are specifically addressed. Sulfate‐reducing bacteria (SRB) are core members of DMW. However, their roles are not entirely clear, and they remain largely uncultured. We found support for their remarkable diversity and taxonomic novelty by mining metagenome‐assembled genomes from the Black Sea as model ecosystem. We highlight recent insights into the metabolism of key sulfur‐oxidizing SUP05 and Sulfurimonas bacteria, and discuss the probable involvement of uncultivated SAR324 and BS‐GSO2 bacteria in sulfur oxidation. Uncultivated Marinimicrobia bacteria with a presumed organoheterotrophic metabolism are abundant in DMW. Like SRB, they may use specific molybdoenzymes to conserve energy from the oxidation, reduction or disproportionation of sulfur cycle intermediates such as S0 and thiosulfate, produced from the oxidation of sulfide. We expect that tailored sampling methods and a renewed focus on cultivation will yield deeper insight into sulfur‐cycling bacteria in DMW.

Nutrient enrichment increases size of Zostera marina shoots and enriches for sulfur and nitrogen cycling bacteria in root-associated microbiomes.

Seagrasses are vital coastal ecosystem engineers, which are mutualistically associated with microbial communities that contribute to the ecosystem services provided by meadows. The seagrass microbiome and sediment microbiota play vital roles in belowground biogeochemical and carbon cycling. These activities are influenced by nutrient, carbon and oxygen availability, all of which are modulated by environmental factors and plant physiology. Seagrass meadows are increasingly threatened by nutrient pollution, and it is unknown how the seagrass microbiome will respond to this stressor. We investigated the effects of fertilization on the physiology, morphology and microbiome of eelgrass (Zostera marina) cultivated over 4 weeks in mesocosms. We analyzed the community structure associated with eelgrass leaf, root and rhizosphere microbiomes, and of communities from water column and bulk sediment using 16S rRNA amplicon sequencing. Fertilization led to a higher number of leaves compared with that of eelgrass kept under ambient conditions. Additionally, fertilization led to enrichment of sulfur and nitrogen bacteria in belowground communities. These results suggest nutrient enrichment can stimulate belowground biogeochemical cycling, potentially exacerbating sulfide toxicity in sediments and decreasing future carbon sequestration stocks.

Functional Groups of Bacteria and Their Involvement in Geochemical Processes in Microbial Communities of Mineral Sources in Sakhalin Island (Far East, Russia)

The chemical composition of mineral waters as well as the diversity, quantity and distribution peculiarities of different functional groups of bacteria in microbial mats in Sakhalin mineral springs was studied. The prevalence of sodium cations in the composition of bicarbonate anions and chloride ions was noticed. The studied waters were substantially enriched with silicone, iodine, boron, iron and strontium. It was established that the main morphogenic bacteria in the mats of cold springs were the colorless sulfur bacteria Thiotrix sp. The microbial mats formed at the outlets of Sakhalin mineral springs contain a high quantity of different functional bacteria groups that play an important role in the geochemical cycles of carbon, nitrogen, sulfur, iron and manganese. Prevalence of bacteria of sulfur and carbon cycles is a peculiarity of microbial mats in Antonovsky and Nevelsky mineral waters. The important role of sulfur cycle bacteria is confirmed by high quantities of thionic, sulfate-reducing bacteria and colorless sulfur bacteria. The mat of Alexandrovsky thermal spring contains a high amount of bacteria of carbon and nitrogen geochemical cycles; an important role of these microorganisms in mat’s functioning is shown. Pure bacterial cultures were isolated; they mostly include gram-positive, spore-forming motile rods Bacillus sp.

Response of the Intertidal Microbial Community Structure and Metabolic Profiles to Zinc Oxide Nanoparticle Exposure.

The toxicity of nanomaterials to microorganisms is related to their dose and environmental factors. The aim of this study was to investigate the shifts in the microbial community structure and metabolic profiles and to evaluate the environmental factors in a laboratory scale intertidal wetland system exposed to zinc oxide nanoparticles (ZnO NPs). Microbial assemblages were determined using 16S rRNA high-throughput sequencing. Community-level physiological profiles were determined using Biolog-ECO technology. Results showed Proteobacteria was the predominant (42.6%–55.8%) phylum across all the sediments, followed by Bacteroidetes (18.9%–29.0%). The genera Azoarcus, Maribacter, and Thauera were most frequently detected. At the studied concentrations (40 mg·L−1, 80 mg·L−1, 120 mg·L−1), ZnO NPs had obvious impacts on the activity of Proteobacteria. Adverse effects were particularly evident in sulfur and nitrogen cycling bacteria such as Sulfitobacter, unidentified_Nitrospiraceae, Thauera, and Azoarcus. The alpha diversity index of microbial community did not reflect stronger biological toxicity in the groups with high NP concentrations (80 mg·L−1, 120 mg·L−1) than the group with low NP concentration (40 mg·L−1). The average well color development (AWCD) values of periodically submersed groups were higher than those of long-term submersed groups. The group with NP concentration (40 mg·L−1) had the lowest AWCD value; those of the groups with high NP concentrations (80 mg·L−1, 120 mg·L−1) were slightly lower than that of the control group. The beta diversity showed that tidal activity shaped the similar microbial community among the periodically submerged groups, as well as the long-term submerged groups. The groups with high DO concentrations had higher diversity of the microbial community, better metabolic ability, and stronger resistance to ZnO NPs than the groups with a low DO concentration.

Remediation of Crude Oil-Polluted Soil by the Bacterial Rhizosphere Community of Suaeda salsa Revealed by 16S rRNA Genes.

Crude oil pollution of soil is a serious environmental issue, and bioremediation using plants and microorganisms is a natural and sustainable method for its restoration. Pot incubation of a two-factor randomized block (plants with two levels, and crude oil with three levels) was designed to investigate the rhizosphere bacterial community of Suaeda salsa (L.) Pall. Crude oil contamination of soil was studied at different levels: 2 g/kg (low), 4 g/kg (medium), and 6 g/kg (high) levels. In this study, the physicochemical properties of the collected rhizosphere soil were analyzed. Moreover, the soil bacteria were further identified using the 16S rRNA gene. The effects of S. salsa and crude oil and their interaction on the physiochemical properties of the soil and crude oil degradation were found to be significant. Crude oil significantly influenced the diversity and evenness of bacteria, while the effects of S. salsa and interaction with crude oil were not significant. Proteobacteria were found to be dominant at the phylum level. Meanwhile, at the genera level, Saccharibacteria and Alcanivorax increased significantly in the low and medium contamination treatment groups with S. salsa, whereas Saccharibacteria and Desulfuromonas were prevalent in the high contamination treatment group. High crude oil contamination led to a significant decrease in the bacterial diversity in soil, while the effects of S. salsa and its interaction were not significant. Despite the highest abundance of crude oil degradation bacteria, S. salsa reduced crude oil degradation bacteria and increased bacteria related to sulfur, phosphorus, and nitrogen cycling in the low and high contamination group, whereas the opposite effect was observed for the medium contamination treatment group. The abundance of most crude oil degradation bacteria is negatively correlated with crude oil content. Nitrogen cycling bacteria are sensitive to the total nitrogen, total phosphorus, ammonia nitrogen, and nitrate nitrogen, and pH of the soil. Sulfur cycling bacteria are sensitive to aromatic hydrocarbons, saturated hydrocarbons, and asphaltene in soil. This research is helpful for further studying the mechanism of synergistic degradation by S. salsa and bacteria.

Root microbiomes as indicators of seagrass health.

The development of early warning indicators that identify ecosystem stress is a priority for improving ecosystem management. As microbial communities respond rapidly to environmental disturbance, monitoring their composition could prove one such early indicator of environmental stress. We combined 16S rRNA gene sequencing of the seagrass root microbiome of Halophila ovalis with seagrass health metrics (biomass, productivity and Fsulphide) to develop microbial indicators for seagrass condition across the Swan-Canning Estuary and the Leschenault Estuary (south-west Western Australia); the former had experienced an unseasonal rainfall event leading to declines in seagrass health. Microbial indicators detected sites of potential stress that other seagrass health metrics failed to detect. Genera that were more abundant in 'healthy' seagrasses included putative methylotrophic bacteria (e.g. Methylotenera and Methylophaga), iron cycling bacteria (e.g. Deferrisoma and Geothermobacter) and N2 fixing bacteria (e.g. Rhizobium). Conversely, genera that were more abundant in 'stressed' seagrasses were dominated by putative sulphur-cycling bacteria, both sulphide-oxidising (e.g. Candidatus Thiodiazotropha and Candidatus Electrothrix) and sulphate-reducing (e.g. SEEP-SRB1, Desulfomonile and Desulfonema). The sensitivity of the microbial indicators developed here highlights their potential to be further developed for use in adaptive seagrass management, and emphasises their capacity to be effective early warning indicators of stress.

Informative indices of the biocorrosion activity for the determination of the character of the aggression ground

Underground corrosion is referred to the most difficult types of corrosion in connection with that it is multifactorial and differs in progressive dynamics of the participation of each parameter in the process of destruction of the metal. With the aim of the evaluation of the informativeness of the index of the biocorrosion activity caused by the influence of various factors to determine the character of the soil aggressiveness in the district of pipeline laying there was studied the complex of microbiological and physical-chemical indices). There was determined the amount of sulfur cycle bacteria (autotrophic thiobacteria and sulphate-reducing bacteria), the total concentration of sulfur and iron in the soil samples adjacent to the surface of the underground pipelines in the territory of the Khanty-Mansi Autonomous District of Yugra, and the ratio of these indices with a specific electrical resistance of the soil. There was established the predominance ofsamples with weak aggressiveness of the soil (55.17% of cases), with the criterion ofbiocorrosion soil activity of 2,44 ± 0,19. The results show significant differences in the thiobacteria content and mobile iron in the studied soil-ground samples. There was revealed a direct correlation of the average force of concentrations of identified bacteria and iron content in the soil. There was shown the necessity of the implementation of dynamic control and the development of methods of protection of metal structures to prevent biocorrosion in the design and in the process of the operation of the pipeline.

Exploring Biodiversity and Arsenic Metabolism of Microbiota Inhabiting Arsenic-Rich Groundwaters in Northern Italy.

Arsenic contamination of groundwater aquifers is an issue of global concern. Among the affected sites, in several Italian groundwater aquifers arsenic levels above the WHO limits for drinking water are present, with consequent issues of public concern. In this study, for the first time, the role of microbial communities in metalloid cycling in groundwater samples from Northern Italy lying on Pleistocene sediments deriving from Alps mountains has been investigated combining environmental genomics and cultivation approaches. 16S rRNA gene libraries revealed a high number of yet uncultured species, which in some of the study sites accounted for more of the 50% of the total community. Sequences related to arsenic-resistant bacteria (arsenate-reducing and arsenite-oxidizing) were abundant in most of the sites, while arsenate-respiring bacteria were negligible. In some of the sites, sulfur-oxidizing bacteria of the genus Sulfuricurvum accounted for more than 50% of the microbial community, whereas iron-cycling bacteria were less represented. In some aquifers, arsenotrophy, growth coupled to autotrophic arsenite oxidation, was suggested by detection of arsenite monooxygenase (aioA) and 1,5-ribulose bisphosphate carboxylase (RuBisCO) cbbL genes of microorganisms belonging to Rhizobiales and Burkholderiales. Enrichment cultures established from sampled groundwaters in laboratory conditions with 1.5 mmol L-1 of arsenite as sole electron donor were able to oxidize up to 100% of arsenite, suggesting that this metabolism is active in groundwaters. The presence of heterotrophic arsenic resistant bacteria was confirmed by enrichment cultures in most of the sites. The overall results provided a first overview of the microorganisms inhabiting arsenic-contaminated aquifers in Northern Italy and suggested the importance of sulfur-cycling bacteria in the biogeochemistry of arsenic in these ecosystems. The presence of active arsenite-oxidizing bacteria indicates that biological oxidation of arsenite, in combination with arsenate-adsorbing materials, could be employed for metalloid removal.

Metagenomic insights into diazotrophic communities across Arctic glacier forefields.

Microbial nitrogen fixation is crucial for building labile nitrogen stocks and facilitating higher plant colonisation in oligotrophic glacier forefield soils. Here, the diazotrophic bacterial community structure across four Arctic glacier forefields was investigated using metagenomic analysis. In total, 70 soil metagenomes were used for taxonomic interpretation based on 185 nitrogenase (nif) sequences, extracted from assembled contigs. The low number of recovered genes highlights the need for deeper sequencing in some diverse samples, to uncover the complete microbial populations. A key group of forefield diazotrophs, found throughout the forefields, was identified using a nifH phylogeny, associated with nifH Cluster I and III. Sequences related most closely to groups including Alphaproteobacteria, Betaproteobacteria, Cyanobacteria and Firmicutes. Using multiple nif genes in a Last Common Ancestor analysis revealed a diverse range of diazotrophs across the forefields. Key organisms identified across the forefields included Nostoc, Geobacter, Polaromonas and Frankia. Nitrogen fixers that are symbiotic with plants were also identified, through the presence of root associated diazotrophs, which fix nitrogen in return for reduced carbon. Additional nitrogen fixers identified in forefield soils were metabolically diverse, including fermentative and sulphur cycling bacteria, halophiles and anaerobes.