Microbially mediated sulfur oxidation coupled with arsenate reduction within oligotrophic mining-impacted habitats.

Arsenate reduction is a major cause of As release from soils which threatens more than 200 million people worldwide. While heterotrophic As(V) reduction has been investigated extensively, the mechanism of chemolithotrophic As(V) reduction is less studied. Since As is frequently found as sulfidic minerals in the environment, microbial mediated sulfur oxidation coupled to As(V) reduction (SOAsR), a chemolithotrophic process, may be more favorable in oligotrophic mining-impacted sites (e.g., As-contaminated mine tailings). While SOAsR is thermodynamically favorable, knowledge regarding this biogeochemical process is still limited. The current study suggested that SOAsR was a more prevalent process compared to heterotrophic As(V) reduction in oligotrophic sites, such as mine tailings. The water-soluble reduced sulfur concentration was predicted as one of the major geochemical parameters that substantially impacted SOAsR potentials. A combination of DNA-SIP and metagenome binning revealed members of the genera Sulfuricella, Ramlibacter, and Sulfuritalea as sulfur oxidizing As(V)-reducing bacteria (SOAsRB) in mine tailings. Genome mining further expanded the list of potential SOAsRBs to diverse phylogenetic lineages such as members associated with Burkholderiaceae and Rhodocyclaceae. Metagenome analysis using multiple tailing samples across southern China confirmed that the putative SOAsRB were the dominant As(V) reducers in these sites. Together, the current findings expand our knowledge regarding the chemolithotrophic As(V) reduction process, which may be harnessed to facilitate future remediation practices in mine tailings.

Microbial Sulfur and Arsenic Oxidation Facilitate the Establishment of Biocrusts during Reclamation of Degraded Mine Tailings.

Degraded tailings generated by the mining of metal ores are major environmental threats to the surrounding ecosystems. Tailing reclamation, however, is often impeded due to adverse environmental conditions, with depleted key nutrients (i.e., nitrogen (N) and phosphorus (P)) and elevated sulfur and metal(loid) concentrations. Formation of biocrusts may significantly accelerate nutrient accumulation and is therefore an essential stage for tailing reclamation. Although suggested to play an important role, the microbial community composition and key metabolisms in biocrusts remain largely unknown and are therefore investigated in the current study. The results suggested that sulfur and arsenic oxidation are potential energy sources utilized by members of predominant biocrust bacterial families, including Beijerinckiaceae, Burkholderiaceae, Hyphomicrobiaceae, and Rhizobiaceae. Accordingly, the S and As oxidation potentials are elevated in biocrusts compared to those in their adjacent tailings. Biocrust growth, as proxied by chlorophyll concentrations, is enhanced in treatments supplemented with S and As. The elevated biocrust growth might benefit from nutrient acquisition services (i.e., nitrogen fixation and phosphorus solubilization) fueled by microbial sulfur and arsenic oxidation. The current study suggests that sulfur- and arsenic-oxidizing microorganisms may play important ecological roles in promoting biocrust formation and facilitating tailing reclamation.

Differential Mechanisms of Microbial As(III) and Sb(III) Oxidation and Their Contribution to Tailings Reclamation.

Mine tailings are extremely oligotrophic environments frequently contaminated with elevated As and Sb, making As(III) and Sb(III) oxidation potentially important energy sources for the tailing microbiome. Although they have been proposed to share similar metabolic pathways, a systemic comparison of the As(III) and Sb(III) oxidation mechanisms and energy utilization efficiencies requires further elucidation. In this study, we employed a combination of physicochemical, molecular, and bioinformatic analyses to compare the kinetic and genetic mechanisms of As(III) and Sb(III) oxidation as well as their respective energy efficiencies for fueling the key nutrient acquisition metabolisms. Thiobacillus and Rhizobium spp. were identified as functional populations for both As(III) and Sb(III) oxidation in mine tailings by DNA-stable isotope probing. However, these microorganisms mediated As(III) and Sb(III) oxidation via different metabolic pathways, resulting in preferential oxidation of Sb(III) over As(III). Notably, both As(III) and Sb(III) oxidation can facilitate nitrogen fixation and phosphate solubilization in mine tailings, with Sb(III) oxidation being more efficient in powering these processes. Thus, this study provided novel insights into the microbial As(III) and Sb(III) oxidation mechanisms and their respective nutrient acquisition efficiencies, which may be critical for the reclamation of mine tailings.

Bacteria associated with Comamonadaceae are key arsenite oxidizer associated with Pteris vittata root.

Pteris vittata (P. vittata), an arsenic (As) hyperaccumulator commonly used in the phytoremediation of As-contaminated soils, contains root-associated bacteria (RAB) including those that colonize the root rhizosphere and endosphere, which can adapt to As contamination and improve plant health. As(III)-oxidizing RAB can convert the more toxic arsenite (As(III)) to less toxic arsenate (As(V)) under As-rich conditions, which may promote plant survial. Previous studies have shown that microbial As(III) oxidation occurs in the rhizospheres and endospheres of P. vittata. However, knowledge of RAB of P. vittata responsible for As(III) oxidation remained limited. In this study, members of the Comamonadaceae family were identified as putative As(III) oxidizers, and the core microbiome associated with P. vittata roots using DNA-stable isotope probing (SIP), amplicon sequencing and metagenomic analysis. Metagenomic binning revealed that metagenome assembled genomes (MAGs) associated with Comamonadaceae contained several functional genes related to carbon fixation, arsenic resistance, plant growth promotion and bacterial colonization. As(III) oxidation and plant growth promotion may be key features of RAB in promoting P. vittata growth. These results extend the current knowledge of the diversity of As(III)-oxidizing RAB and provide new insights into improving the efficiency of arsenic phytoremediation.

Phototrophic Nitrogen Fixation, a Neglected Biogeochemical Process in Mine Tailings?

Biological nitrogen fixation (BNF) has important ecological significance in mine tailing by contributing to the initial accumulation of nitrogen. In addition to chemolithotrophic and heterotrophic BNF, light may also fuel BNF in oligotrophic mine tailings. However, knowledge regarding the occurrence and ecological significance of this biogeochemical process in mine tailings remains ambiguous. The current study observed phototrophic BNF in enrichment cultures established from three primary successional stages (i.e., original tailings, biological crusts, and pioneer plants) of tailings. Notably, phototrophic BNF in tailings may be more active at vegetation stages (i.e., biological crusts and pioneering plants) than in bare tailings. DNA-stable isotope probing identified Roseomonas species as potential aerobic anoxygenic phototrophs responsible for phototrophic BNF. Furthermore, metagenomic binning as well as genome mining revealed that Roseomonas spp. contained essential genes involved in nitrogen fixation, anoxygenic photosynthesis, and carbon fixation, suggesting their genetic potential to mediate phototrophic BNF. A causal inference framework equipped with the structural causal model suggested that the enrichment of putative phototrophic diazotrophic Roseomonas may contribute to an elevated total nitrogen content during primary succession in these mine tailings. Collectively, our findings suggest that phototrophic diazotrophs may play important roles in nutrient accumulation and hold the potential to facilitate ecological succession in tailings.

Microbial-mediated oxidative dissolution of orpiment and realgar in circumneutral aquatic environments.

Arsenic (As) is a toxic metalloid that causes severe environmental contamination worldwide. Upon exposure to aqueous phases, the As-bearing minerals, such as orpiment (As2S3) and realgar (As4S4), undergo oxidative dissolution, in which biotic and abiotic activities both contributed significant roles. Consequently, the dissolved As and S are rapidly discharged through water transportation to broader regions and contaminate surrounding areas, especially in aquatic environments. Despite both orpiment and realgar are frequently encountered in carbonate-hosted neutral environments, the microbial-mediated oxidative dissolution of these minerals, however, have been primarily investigated under acidic conditions. Therefore, the current study aimed to elucidate microbial-mediated oxidative dissolution under neutral aquatic conditions. The current study demonstrated that the dissolution of orpiment and realgar is synergistically regulated by abiotic (i.e., specific surface area (SSA) of the mineral) and biotic (i.e., microbial oxidation) factors. The initial dissolution of As(III) and S2- from minerals is abiotically impacted by SSA, while the microbial oxidation of As(III) and S2- accelerated the overall dissolution rates of orpiment and realgar. In As-contaminated environments, members of Thiobacillus and Rhizobium were identified as the major populations that mediated oxidative dissolution of orpiment and realgar by DNA-stable isotope probing. This study provides novel insights regarding the microbial-mediated oxidative dissolution process of orpiment and realgar under neutral conditions.

Selective pressure of arsenic and antimony co-contamination on microbial community in alkaline sediments.

Although response of microbial community to arsenic (As) and antimony (Sb) co-contamination has been investigated in neutral and acidic environments, little is known in alkaline environment. Herein, the microbial response and survival strategies under the stress of As and Sb co-contamination were determined in the alkaline sediments. Elevated concentrations of As (13700 ± 5012 mg/kg) and Sb (10222 ± 1619 mg/kg) were introduced into the alkaline sediments by the mine drainage, which was partially adopted in the aquatic environment and resulted in a relatively lower contamination (As, 6633 ± 1707 mg/kg; Sb, 6108 ± 1095 mg/kg) in the downstream sediments. The microbial richness was significantly damaged and the microbial compositions were dramatically shifted by the As and Sb co-contamination. Metagenomic analysis shed light on the survival strategies of the microbes under the pressure of As and Sb co-contamination including metal oxidation coupled with denitrification, metal reduction, and metal resistance. The representative microbes were revealed in the sediments with higher (Halomonas) and lower (Thiobacillus, Hydrogenophaga and Flavihumibacter) As and Sb concentration, respectively. In addition, antibiotic resistance genes were found to co-occur with metal resistance genes in the assembled bins. These findings might provide theoretical guidance for bioremediation of As and Sb co-contamination in alkaline environment.

Anaerobic selenite-reducing bacteria and their metabolic potentials in Se-rich sediment revealed by the combination of DNA-stable isotope probing, metagenomic binning, and metatranscriptomics.

Microorganisms play a critical role in the biogeochemical cycling of selenium (Se) in aquatic environments, particularly in reducing the toxicity and bioavailability of selenite (Se(IV)). This study aimed to identify putative Se(IV)-reducing bacteria (SeIVRB) and investigate the genetic mechanisms underlying Se(IV) reduction in anoxic Se-rich sediment. Initial microcosm incubation confirmed that Se(IV) reduction was driven by heterotrophic microorganisms. DNA stable-isotope probing (DNA-SIP) analysis identified Pseudomonas, Geobacter, Comamonas, and Anaeromyxobacter as putative SeIVRB. High-quality metagenome-assembled genomes (MAGs) affiliated with these four putative SeIVRB were retrieved. Annotation of functional gene indicated that these MAGs contained putative Se(IV)-reducing genes such as DMSO reductase family, fumarate and sulfite reductases. Metatranscriptomic analysis of active Se(IV)-reducing cultures revealed significantly higher transcriptional levels of genes associated with DMSO reductase (serA/PHGDH), fumarate reductase (sdhCD/frdCD), and sulfite reductase (cysDIH) compared to those in cultures not amended with Se(IV), suggesting that these genes played important roles in Se(IV) reduction. The current study expands our knowledge of the genetic mechanisms involved in less-understood anaerobic Se(IV) bio-reduction. Additinally, the complementary abilities of DNA-SIP, metagenomics, and metatranscriptomics analyses are demonstrated in elucidating the microbial mechanisms of biogeochemical processes in anoxic sediment.

Removal of toilet paper fibers from residential wastewater: a life cycle assessment.

Toilet paper has been reported as one of the major insoluble pollutant components in the influent of wastewater treatment plants. Toilet paper fibers contribute to a large production of sewage sludge, resulting in a high treatment cost and high energy consumption. To find energy-efficient, cost-effective, and environment-friendly technologies for fiber removal and resource recovery from wastewater, a life-cycle assessment (LCA) was performed to analyze the wastewater treatment processes, including a sieving process for removing and recovering suspended solids before the biodegradation units. Based on the LCA results, it was estimated that the sieve screening process saved 8.57% of energy consumption. The construction phase of sieving consumed 1.31% energy cost compared with the operation phase. Environmental impact analysis showed that sieving reduced the impacts of climate change, human toxicity, fossil depletion, and particulate matter formation, which reduced the total normalized environmental impacts by 9.46%. The life-cycle analysis of the removal of toilet paper fibers from wastewater revealed the need to use more efficient methods to enhance the recovery of cellulose fibers.

MiR-92a expression profiling of exfoliated colonocytes isolated from feces for colorectal cancer screening.

OBJECTIVE: This study seeks to assess the efficacy of exfoliated colonocytes isolated from feces (ECIF) miR-92a as a clinical colorectal cancer diagnostic marker in a larger cohort. METHODS: Clinicopathologic data from colorectal cancer patients and health controls that underwent colonoscopy, as well as patients of other cancers diagnosed, were included. A total of 963 Chinese participants were enrolled, with 292 (27.4%) having colorectal cancer, 140 (14.5%) having other types of cancer, e.g., pancreatic, liver, oral, bile duct, esophagus, and stomach cancer, 171 (17.8%) having infection in the intestine, rectal, stomach, appendix, and gastrointestinal ulcer, and 360 (37.4%) of healthy controls. ECIF samples were gathered and miR-92a levels were detected using TaqMan probe-based miR-92a real-time quantitative PCR (RT-qPCR) kit developed by Shenzhen GeneBioHealth Co., Ltd. RESULTS: Through a series of experiments, we demonstrated that the Ep-LMB/Vi-LMB magnetic separation system is feasible, highly specific, and highly sensitive at a cutoff value of 1053 copies per 6 ng of ECIF RNA. ECIF miR-92a levels were significantly higher in colorectal cancer patients than in controls. Colorectal cancer detection sensitivity and specificity were 87.3% and 86.9% respectively. Furthermore, the performance of this miR-92a detection kit demonstrated that it is an effective tool for colorectal cancer, with a high sensitivity of 84.1%, even in early cancer stages (0, I, and II). Furthermore, tumor removal resulted in lower stool miR-92a levels (3.21±0.58 vs. 2.14±1.14, P < 0.0001, n = 65). CONCLUSION: Finally, the miR-92a RT-qPCR kit detects ECIF-increased miR-92a and could be used for colorectal cancer screening.

Arsenic (As) oxidation by core endosphere microbiome mediates As speciation in Pteris vittata roots.

Pteris vittata is an arsenic(As)-hyperaccumulator that may be employed in phytoremediation of As-contaminated soils. P. vittata-associated microbiome are adapted to elevated As and may be important for host survival under stresses. Although P. vittata root endophytes could be critical for As biotransformation in planta, their compositions and metabolisms remain elusive. The current study aims to characterize the root endophytic community composition and As-metabolizing potentials in P. vittata. High As(III) oxidase gene abundances and rapid As(III) oxidation activity indicated that As(III) oxidation was the dominant microbial As-biotransformation processes compared to As reduction and methylization in P. vittata roots. Members of Rhizobiales were the core microbiome and the dominant As(III) oxidizers in P. vittata roots. Acquasition of As-metabolising genes, including both As(III) oxidase and As(V) detoxification reductase genes, through horizontal gene transfer was identified in a Saccharimonadaceae genomic assembly, which was another abundant population residing in P. vittata roots. Acquisition of these genes might improve the fitness of Saccharimonadaceae population to elevated As concentrations in P. vittata. Diverse plant growth promoting traits were encoded by the core root microbiome populations Rhizobiales. We propose that microbial As(III) oxidation and plant growth promotion are critical traits for P. vittata survival in hostile As-contaiminated sites.

Chemolithotrophic Biological Nitrogen Fixation Fueled by Antimonite Oxidation May Be Widespread in Sb-Contaminated Habitats.

Nitrogen (N) deficiency in mining-contaminated habitats usually hinders plant growth and thus hampers tailing revegetation. Biological N fixation (BNF) is an essential biogeochemical process that contributes to the initial accumulation of N in oligotrophic mining-contaminated regions. Previous studies reported that chemolithotrophic rather than heterotrophic diazotrophs frequently dominated in the mining-contaminated regions. Chemolithotrophic diazotrophs may utilize elements abundant in such habitats (e.g., sulfur (S), arsenic (As), and antimony (Sb)) as electron donors to fix N2. BNF fueled by the oxidation of S and As has been detected in previous studies. However, BNF fueled by Sb(III) oxidation (Sb-dependent BNF) has never been reported. The current study observed the presence of Sb-dependent BNF in slurries inoculated from Sb-contaminated habitats across the South China Sb belt, suggesting that Sb-dependent BNF may be widespread in this region. DNA-stable isotope probing identified bacteria associated with Rhodocyclaceae and Rhizobiaceae as putative microorganisms responsible for Sb-dependent BNF. Furthermore, metagenomic-binning demonstrated that Rhodocyclaceae and Rhizobiaceae contained essential genes involved in Sb(III) oxidation, N2 fixation, and carbon fixation, suggesting their genetic potential for Sb-dependent BNF. In addition, meta-analysis indicated that these bacteria are widespread among Sb-contaminated habitats with different niche preferences: Rhodocyclaceae was enriched in river sediments and tailings, while Rhizobiaceae was enriched only in soils. This study may broaden our fundamental understanding of N fixation in Sb-mining regions.

Characterization of diazotrophic root endophytes in Chinese silvergrass (Miscanthus sinensis).

BACKGROUND: Phytoremediation is a potentially cost-effective way to remediate highly contaminated mine tailing sites. However, nutrient limitations, especially the deficiency of nitrogen (N), can hinder the growth of plants and impair the phytoremediation of mine tailings. Nevertheless, pioneer plants can successfully colonize mine tailings and exhibit potential for tailing phytoremediation. Diazotrophs, especially diazotrophic endophytes, can promote the growth of their host plants. This was tested in a mine-tailing habitat by a combination of field sampling, DNA-stable isotope probing (SIP) analysis, and pot experiments. RESULTS: Bacteria belonging to the genera Herbaspirillum, Rhizobium, Devosia, Pseudomonas, Microbacterium, and Delftia are crucial endophytes for Chinese silvergrass (Miscanthus sinensis) grown in the tailing, the model pioneer plant selected in this study. Further, DNA-SIP using 15N2 identified Pseudomonas, Rhizobium, and Exiguobacterium as putative diazotrophic endophytes of M. sinensis. Metagenomic-binning suggested that these bacteria contained essential genes for nitrogen fixation and plant growth promotion. Finally, two diazotrophic endophytes Rhizobium sp. G-14 and Pseudomonas sp. Y-5 were isolated from M. sinensis. Inoculation of another pioneer plant in mine tailings, Bidens pilosa, with diazotrophic endophytes resulted in successful plant colonization, significantly increased nitrogen fixation activity, and promotion of plant growth. CONCLUSIONS: This study indicated that diazotrophic endophytes have the potential to promote the growth of pioneer plant B. pilosa in mine tailings. Video Abstract.

Vanadate reducing bacteria and archaea may use different mechanisms to reduce vanadate in vanadium contaminated riverine ecosystems as revealed by the combination of DNA-SIP and metagenomic-binning.

Vanadium (V) is a transitional metal that poses health risks to exposed humans. Microorganisms play an important role in remediating V contamination by reducing more toxic and mobile vanadate (V(V)) to less toxic and mobile V(IV). In this study, DNA-stable isotope probing (SIP) coupled with metagenomic-binning was used to identify microorganisms responsible for V(V) reduction and determine potential metabolic mechanisms in cultures inoculated with a V-contaminated river sediment. Anaeromyxobacter and Geobacter spp. were identified as putative V(V)-reducing bacteria, while Methanosarcina spp. were identified as putative V(V)-reducing archaea. The bacteria may use the two nitrate reductases NarG and NapA for respiratory V(V) reduction, as has been demonstrated previously for other species. It is proposed that Methanosarcina spp. may reduce V(V) via anaerobic methane oxidation pathways (AOM-V) rather than via respiratory V(V) reduction performed by their bacterial counterparts, as indicated by the presence of genes associated with anaerobic methane oxidation coupled with metal reduction in the metagenome assembled genome (MAG) of Methanosarcina. Briefly, methane may be oxidized through the "reverse methanogenesis" pathway to produce electrons, which may be further captured by V(V) to promote V(V) reduction. More specially, V(V) reduction by members of Methanosarcina may be driven by electron transport (CoMS-SCoB heterodisulfide reductase (HdrDE), F420H2 dehydrogenases (Fpo), and multi-heme c-type cytochrome (MHC)). The identification of putative V(V)-reducing bacteria and archaea and the prediction of their different pathways for V(V) reduction expand current knowledge regarding the potential fate of V(V) in contaminated sites.

Response of soil protists to antimony and arsenic contamination.

Microorganisms can mediate antimony (Sb) and arsenic (As) transformation and thus change their mobility and toxicity. Having similar geochemical behavior, Sb and As are generally considered to exert similar environmental pressure on microbiome. However, it needs further validation, especially for protists. In this study, the responses of protistan communities to Sb and As were investigated by collecting soils from Xikuangshan Sb mine and Shimen As mine in China. Antimony and As contamination taxonomically and functionally (consumer and phototroph) changed the alpha and beta diversities of protistan communities, but exerted different impacts on the parasitic community. Based on multiple statistical tools, As contamination had a greater impact on protistan communities than Sb. The ecological networks of highly contaminated sites were less complex but highly positively connected compared to less contaminated sites. High As contamination raised the ratio of consumers and decreased the ratio of phototrophs in ecological networks, while the opposite tendency was observed in Sb contaminated soils. High Sb and As contamination enriched different keystone taxa resistant to Sb and As. These results demonstrate that protistan community respond differently to Sb and As.

Clinical Significance of Detection of Peripheral Blood VASP Level in Lung Cancer Patients.

This paper explores the relationship between the clinical value of vasodilator-stimulated phosphoprotein (VASP) in lung cancer tissue and its diagnosis and severity. Totally 100 patients who were clinically diagnosed with lung cancer from January 2018 to December 2020 were enrolled in our study. They were assigned into two groups according to the presence of lymph node metastasis. The VASP levels were measured by flow cytometry. The correlation between the expression of VASP in tumor tissue and the clinical characteristics and prognosis in patients was analyzed. The diagnostic efficacy of plasma VASP with squamous cell carcinoma antigen (SCC), neuron-specific enolase (NSE), cytokeratin-19 fragment (CYFRA21-1), prosecretin-releasing peptide (proGRP), and lung cancer was analyzed. The results were compared with APACHE III score to evaluate the accuracy of VASP in determining the severity of patients. This paper finds that the value of VASP in the non-lymph node metastasis group was significantly higher than that in the healthy control group, and the VASP level in the lymph node metastasis group was significantly higher than that in the non-lymph node metastasis group and the healthy control group (all p values <0.05). The APACHE III score of the lymph node metastasis group was higher than that of the non-lymph node metastasis group (p value <0.05). The diagnostic efficacy of VASP is similar to that of SCC, NSE, CYFRA21-1, and proGRP. The plasma VASP value was statistically different in the survival group and the death group, with higher level observed in the death group compared to survival group (all p values <0.05). The value of plasma VASP alone and acute physiology and chronic health evaluations III (APACHE III) score for lung cancer mortality was similar (47.06% vs. 52.94%, p value >0.05). Similar accuracy was observed in VASP and APACHE III score in predicting mortality of lung cancer (84.37% vs. 85.77%, p value>0.05). This paper concludes that the level of VASP correlates to the severity of the lung cancer and survival of the patients.

Reverse Adverse Immune Microenvironments by Biomaterials Enhance the Repair of Spinal Cord Injury.

Spinal cord injury (SCI) is a severe and traumatic disorder that ultimately results in the loss of motor, sensory, and autonomic nervous function. After SCI, local immune inflammatory response persists and does not weaken or disappear. The interference of local adverse immune factors after SCI brings great challenges to the repair of SCI. Among them, microglia, macrophages, neutrophils, lymphocytes, astrocytes, and the release of various cytokines, as well as the destruction of the extracellular matrix are mainly involved in the imbalance of the immune microenvironment. Studies have shown that immune remodeling after SCI significantly affects the survival and differentiation of stem cells after transplantation and the prognosis of SCI. Recently, immunological reconstruction strategies based on biomaterials have been widely explored and achieved good results. In this review, we discuss the important factors leading to immune dysfunction after SCI, such as immune cells, cytokines, and the destruction of the extracellular matrix. Additionally, the immunomodulatory strategies based on biomaterials are summarized, and the clinical application prospects of these immune reconstructs are evaluated.

Desulfurivibrio spp. mediate sulfur-oxidation coupled to Sb(V) reduction, a novel biogeochemical process.

Antimony (Sb) contamination released from mine tailings represents a global threat to natural ecosystems and human health. The geochemical conditions of Sb tailings, which are oligotrophic and replete in sulfur (S) and Sb, may promote the coupled metabolism of Sb and S. In this study, multiple lines of evidence indicate that a novel biogeochemical process, S oxidation coupled to Sb(V) reduction, is enzymatically mediated by Desulfurivibrio spp. The distribution of Desulfurivibrio covaried with S and Sb concentrations, showing a high relative abundance in Sb mine tailings but not in samples from surrounding sites (i.e., soils, paddies, and river sediments). Further, the metabolic potential to couple S oxidation to Sb(V) reduction, encoded by a non-canonical, oxidative sulfite reductase (dsr) and arsenate reductase (arrA) or antimonate reductase (anrA), respectively, was found to be common in Desulfurivibrio genomes retrieved from metal-contaminated sites in southern China. Elucidation of enzymatically-catalyzed S oxidation coupled to Sb(V) reduction expands the fundamental understanding of Sb biogeochemical cycling, which may be harnessed to improve remediation strategies for Sb mine tailings.

The composition, biotic network, and assembly of plastisphere protistan taxonomic and functional communities in plastic-mulching croplands.

The increasing use of plastic film mulching has caused the accumulation of plastic film residue in soil. To date, most researches on the plastisphere have focused on bacterial and fungal communities, with few on protistan community, especially in terrestrial ecosystems. To understand plastisphere protistan communities, we collected plastic film residues from plastic-mulching croplands. The plastisphere significantly altered the alpha-diversity, structure, and composition of taxonomic and functional (consumers, phototrophs, and parasites) communities. In both the plastisphere and surrounding soil, although some consumers dominated the protistan community network, while their performance was weakened by mulch application. The ecological networks of the plastisphere community presented higher modularity, less complexity, and a lower proportion of positive connections than the networks of surrounding soil. In addition, the enriched plant pathogens (e.g., Spongospora) and keystone taxa classified as plant pathogens (e.g., Pythium) in the plastisphere imply that plastic film residues may pose a risk to soil health and plant performance. Neutral-based processes dominated the assembly of the plastisphere protistan communities, whereas niche-based processes governed the protistan community assembly of surrounding soil. This study reveals that plastic film residues generate a unique niche for protistan colonization, which disturbs protistan communities and threatens agricultural ecosystem health and function.