Domestication of rice may have changed its arbuscular mycorrhizal properties by modifying phosphorus nutrition-related traits and decreasing symbiotic compatibility.

Modern cultivated rice (Oryza sativa) typically experiences limited growth benefits from arbuscular mycorrhizal (AM) symbiosis. This could be due to the long-term domestication of rice under favorable phosphorus conditions. However, there is limited understanding of whether and how the rice domestication has modified AM properties. This study compared AM properties between a collection of wild (Oryza rufipogon) and domesticated rice genotypes and investigated the mechanisms underlying their differences by analyzing physiological, genomic, transcriptomic, and metabolomic traits critical for AM symbiosis. The results revealed significantly lower mycorrhizal growth responses and colonization intensity in domesticated rice compared to wild rice, and this change of AM properties may be associated with the domestication modifications of plant phosphorus utilization efficiency at physiological and genomic levels. Domestication also resulted in a decrease in the activity of the mycorrhizal phosphorus acquisition pathway, which may be attributed to reduced mycorrhizal compatibility of rice roots by enhancing defense responses like root lignification and reducing carbon supply to AM fungi. In conclusion, rice domestication may have changed its AM properties by modifying P nutrition-related traits and reducing symbiotic compatibility. This study offers new insights for improving AM properties in future rice breeding programs to enhance sustainable agricultural production.

A synthetic bacterial consortium improved the phytoremediation efficiency of ryegrass on polymetallic contaminated soil.

Polymetallic contamination of soils caused by mining activities seriously threatens soil fertility, biodiversity and human health. Bioremediation is thought to be of low cost and has minimal environmental risk but its effectiveness needs to be improved. This study aimed to identify the combined effect of plant growth and microbial strains with different functions on the enhancement of bioremediation of polymetallic contaminated soil. The microbiological mechanism of bioremediation was explored by amplicon sequencing and gene prediction. Soil was collected from polymetallic mine wastelands and a non-contaminated site for use in a pot experiment. Remediation efficiency of this method was evaluated by planting ryegrass and applying a mixed bacterial consortium comprising P-solubilizing, N-fixing and SO4-reducing bacteria. The plant-microbe joint remediation method significantly enhanced the above-ground biomass of ryegrass and soil nutrient contents, and at the same time reduced the content of heavy metals in the plant shoots and soil. The application of the composite bacterial inoculum significantly affected the structure of soil bacterial communities and increased the bacterial diversity and complexity, and the stability of co-occurrence networks. The relative abundance of the multifunctional genera to which the strains belonged showed a significant positive correlation with the soil nutrient content. Genera related to carbon (C), nitrogen (N), phosphorus (P), and sulphur (S) cycling and heavy metal resistance showed an up-regulation trend in heavy metal-contaminated soils after the application of the mixed bacterial consortium. Also, bacterial strains with specific functions in the mixed consortium regulated the expression of genes involved in soil nutrient cycling, and thus assisted in making the soil self-sustainable after remediation. These results suggested that the remediation of heavy metal-contaminated soil needs to give priority to the use of multifunctional bacterial agents.

Functional Guilds, Community Assembly, and Co-occurrence Patterns of Fungi in Metalliferous Mine Tailings Ponds in Mainland China.

Metalliferous mine tailings ponds are generally characterized by low levels of nutrient elements, sustained acidic conditions, and high contents of toxic metals. They represent one kind of extreme environments that are believed to resemble the Earth's early environmental conditions. There is increasing evidence that the diversity of fungi inhabiting mine tailings ponds is much higher than previously thought. However, little is known about functional guilds, community assembly, and co-occurrence patterns of fungi in such habitats. As a first attempt to address this critical knowledge gap, we employed high-throughput sequencing to characterize fungal communities in 33 mine tailings ponds distributed across 18 provinces of mainland China. A total of 5842 fungal phylotypes were identified, with saprotrophic fungi being the major functional guild. The predictors of fungal diversity in whole community and sub-communities differed considerably. Community assembly of the whole fungal community and individual functional guilds were primarily governed by stochastic processes. Total soil nitrogen and total phosphorus mediated the balance between stochastic and deterministic processes of the fungal community assembly. Co-occurrence network analysis uncovered a high modularity of the whole fungal community. The observed main modules largely consisted of saprotrophic fungi as well as various phylotypes that could not be assigned to known functional guilds. The richness of core fungal phylotypes, occupying vital positions in co-occurrence network, was positively correlated with edaphic properties such as soil enzyme activity. This indicates the important roles of core fungal phylotypes in soil organic matter decomposition and nutrient cycling. These findings improve our understanding of fungal ecology of extreme environments.

Pharmacological characterization of the small molecule 03A10 as an inhibitor of α-synuclein aggregation for Parkinson's disease treatment.

Aggregation of α-synuclein, a component of Lewy bodies (LBs) or Lewy neurites in Parkinson's disease (PD), is strongly linked with disease development, making it an attractive therapeutic target. Inhibiting aggregation can slow or prevent the neurodegenerative process. However, the bottleneck towards achieving this goal is the lack of such inhibitors. In the current study, we established a high-throughput screening platform to identify candidate compounds for preventing the aggregation of α-synuclein among the natural products in our in-house compound library. We found that a small molecule, 03A10, i.e., (+)-desdimethylpinoresinol, which is present in the fruits of Vernicia fordii (Euphorbiaceae), modulated aggregated α-synuclein, but not monomeric α-synuclein, to prevent further elongation of α-synuclein fibrils. In α-synuclein-overexpressing cell lines, 03A10 (10 µM) efficiently prevented α-synuclein aggregation and markedly ameliorated the cellular toxicity of α-synuclein fibril seeds. In the MPTP/probenecid (MPTP/p) mouse model, oral administration of 03A10 (0.3 mg· kg-1 ·d-1, 1 mg ·kg-1 ·d-1, for 35 days) significantly alleviated behavioral deficits, tyrosine hydroxylase (TH) neuron degeneration and p-α-synuclein aggregation in the substantia nigra (SN). As the Braak hypothesis postulates that the prevailing site of early PD pathology is the gastrointestinal tract, we inoculated α-synuclein preformed fibrils (PFFs) into the mouse colon. We demonstrated that α-synuclein PFF inoculation promoted α-synuclein pathology and neuroinflammation in the gut and brain; oral administration of 03A10 (5 mg· kg-1 ·d-1, for 4 months) significantly attenuated olfactory deficits, α-synuclein accumulation and neuroinflammation in the olfactory bulb and SN. We conclude that 03A10 might be a promising drug candidate for the treatment of PD. 03A10 might be a novel drug candidate for PD treatment, as it inhibits α-synuclein aggregation by modulating aggregated α-synuclein rather than monomeric α-synuclein to prevent further elongation of α-synuclein fibrils and prevent α-synuclein toxicity in vitro, in an MPTP/p mouse model, and PFF-inoculated mice.

[Guiqi Yiyuan Ointment protects rat left lung from bystander effect of right lung injury induced by ~(12)C~(6+) beam].

This study observed the effects of Guiqi Yiyuan Ointment(GQYY) on the left lung subjecting to bystander effect of right lung injury induced by ~(12)C~(6+) beam in rats and decipher the underlying mechanism from NOD-like receptor protein 3(NLRP3)/apoptosis-associated speck-like protein containing a CARD(ASC)/cysteinyl aspartate specific proteinase-1(caspase-1) pathway. Wistar rats were randomized into 7 groups: blank, model, inhibitor [200 mg·kg~(-1), N-acetylcysteine(NAC)], western drug [140 mg·kg~(-1) amifostine(AMI)], and high-, medium-, and low-dose(4.8, 2.4, and 1.2 g·kg~(-1), respectively) GQYY groups. The model of bystander effect damage was established by 4 Gy ~(12)C~(6+) beam irradiation of the right lung(with the other part shielded by a lead plate). The pathological changes in the lung tissue, the level of reactive oxygen species(ROS) in the lung tissue, and the levels of superoxide dismutase(SOD) and malondialdehyde(MDA) in the serum were observed and measured in each group. Furthermore, the mRNA and protein levels of NLRP3, ASC, caspase-1, and phosphorylated nuclear factor-κB p65(p-NF-κB p65)/nuclear factor-κB p65(NF-κB p65) were determined. Compared with the blank group, the model group showed thickened alveolar wall, narrowed alveolar cavity, and presence of massive red blood cells and inflammatory infiltration in the alveolar wall and alveolar cavity. In addition, the model group showed elevated ROS levels in both left and right lungs, elevated MDA level, lowered SOD level, and up-regulated mRNA and protein levels of NLRP3, ASC, caspase-1, and p-NF-κB p65/NF-κB p65. Compared with the model group, the drug administration in all the groups reduced inflammatory cell infiltration in the lung tissue. The inhibitor group and the western drug group showed enlarged alveolar cavity, thinned interstitium, and reduced inflammation. There was a small amount of alveolar wall rupture in the high-and medium-dose GQYY groups and reduced inflammatory cell infiltration in the low dose GQYY group. Compared with the model group, drug administration lowered level of ROS in the left and right lungs, lowered the MDA level, elevated the SOD level, and down-regulated the mRNA and protein levels of NLRP3, ASC, caspase-1, and p-NF-κB p65/NF-κB p65. GQYY can effectively reduce the damage caused by radiation and bystander effect, which may be associated with the ROS-mediated NLRP3 inflammasome activation.

Functional traits explain the consistent resistance of biodiversity to plant invasion under nitrogen enrichment.

Elton's biotic resistance hypothesis, which posits that diverse communities should be more resistant to biological invasions, has received considerable experimental support. However, it remains unclear whether such a negative diversity-invasibility relationship would persist under anthropogenic environmental change. By using the common ragweed (Ambrosia artemisiifolia) as a model invader, our 4-year grassland experiment demonstrated consistently negative relationships between resident species diversity and community invasibility, irrespective of nitrogen addition, a result further supported by a meta-analysis. Importantly, our experiment showed that plant diversity consistently resisted invasion simultaneously through increased resident biomass, increased trait dissimilarity among residents, and increased community-weighted means of resource-conservative traits that strongly resist invasion, pointing to the importance of both trait complementarity and sampling effects for invasion resistance even under resource enrichment. Our study provides unique evidence that considering species' functional traits can help further our understanding of biotic resistance to biological invasions in a changing environment.

Remarkable effects of microbial factors on soil phosphorus bioavailability: A country-scale study.

Low soil phosphorus (P) bioavailability causes the widespread occurrence of P-limited terrestrial ecosystems around the globe. Exploring the factors influencing soil P bioavailability at large spatial scales is critical for managing these ecosystems. However, previous studies have mostly focused on abiotic factors. In this study, we explored the effects of microbial factors on soil P bioavailability of terrestrial ecosystems using a country-scale sampling effort. Our results showed that soil microbial biomass carbon (MBC) and acid phosphatase were important predictors of soil P bioavailability of agro- and natural ecosystems across China although they appeared less important than total soil P. The two microbial factors had a positive effect on soil P bioavailability of both ecosystem types and were able to mediate the effects of several abiotic factors (e.g., mean annual temperature). Meanwhile, we revealed that soil phytase could affect soil P bioavailability at the country scale via ways similar to those of soil MBC and acid phosphatase, a pattern being more pronounced in agroecosystems than in natural ecosystems. Moreover, we obtained evidence for the positive effects of microbial genes encoding these enzymes on soil P bioavailability at the country scale although their effect sizes varied between the two ecosystem types. Taken together, this study demonstrated the remarkable effects of microbial factors on soil P bioavailability at a large spatial scale, highlighting the importance to consider microbial factors in managing the widespread P-limited terrestrial ecosystems.

Hyperaccumulator Plants from China: A Synthesis of the Current State of Knowledge.

Hyperaccumulator plants are the material basis for phytoextraction research and for practical applications in decontaminating polluted soils and industrial wastes. China's high biodiversity and substantial mineral resources make it a global hotspot for hyperaccumulator plant species. Intensive screening efforts over the past 20 years by researchers working in China have led to the discovery of many different hyperaccumulators for a range of elements. In this review, we present the state of knowledge on all currently reported hyperaccumulator species from China, including Cardamine hupingshanensis (selenium, Se), Dicranopteris dichotoma (rare earth elements, REEs), Elsholtzia splendens (copper, Cu), Phytolacca americana (manganese, Mn), Pteris vittata (arsenic, As), Sedum alfredii, and Sedum plumbizincicola (cadmium/zinc, Cd/Zn). This review covers aspects of the ecophysiology and molecular biology of tolerance and hyperaccumulation for each element. The major scientific advances resulting from the study of hyperaccumulator plants in China are summarized and synthesized.

Field comparison of the effectiveness of agricultural and nonagricultural organic wastes for aided phytostabilization of a Pb-Zn mine tailings pond in Hunan Province, China.

To date, very few attempts have been made to systematically compare the effectiveness of agricultural and nonagricultural organic wastes for aided phytostabilization of mine tailings under field conditions. In this study, we performed a field trial to compare the effectiveness of three agricultural organic wastes: chicken manure (CM), crop straw (CS), and spent mushroom compost (SMC), with that of three nonagricultural organic wastes, municipal sludge (MS), medicinal herb residues (MHR), and sweet sorghum vinasse (SSV) for aided phytostabilization of a Pb-Zn mine tailings pond in Hunan Province, China. Eight plant species naturally established in the vicinity of the mine were selected and seeded onto trial plots. It was found that the CM-amended plots had the highest (p < 0.05) vegetation cover (86%) and biomass production (881 g m-2), compared to other treatments. CM was also one of the best amendments in terms of improving soil nutrient status, increasing activities of soil enzymes, and immobilizing soil Pb. In addition, CM-amended plots were characterized by their higher microbial diversity and distinct microbial community structure as compared to the control plots. MS was the second best amendment in promoting vegetation cover (71%) and biomass production (461 g m-2), and it performed as well as CM for improving nutrient status, immobilizing heavy metals, and increasing the activities of enzymes in the mine tailings. Suggestions for further lines of research are made in order to develop future investigations.

Explaining ecosystem multifunction with evolutionary models.

Ecosystem function is the outcome of species interactions, traits, and niche overlap - all of which are influenced by evolution. However, it is not well understood how the tempo and mode of niche evolution can influence ecosystem function. In evolutionary models where either species differences accumulate through random drift in a single trait or species differences accumulate through divergent selection among close relatives, we should expect that ecosystem function is strongly related to diversity. However, when strong selection causes species to converge on specific niches or when novel traits that directly affect function evolve in some clades but not others, the relationship between diversity and ecosystem function might not be very strong. We test these ideas using a field experiment that established plant mixtures with differing phylogenetic diversities and we measured ten different community functions. We show that some functions were strongly predicted by species richness and mean pairwise phylogenetic distance (MPD, a measure of phylogenetic diversity), including biomass production and the reduction of herbivore and pathogen damage in polyculture, while other functions had weaker (litter production and structural complexity) or nonsignificant relationships (e.g., flower production and arthropod abundance) with MPD and richness. However, these divergent results can be explained by different models of niche evolution. These results show that diversity-ecosystem function relationships are the product of evolution, but that the nature of how evolution influences ecosystem function is complex.

[Relationship between seedling grade of Codonopsis pilosula and yield and quality of medicinal materials].

The study is aimed to research the relationship between the seedling grade of Codonopsis pilosula and yield and quality of medicinal materials, so as to provide basis for establishing seedling standard. Thirty seedlings of C. pilosula were collected from the main production areas in Gansu province, such as Weiyuan, Minxian, Zhangxian, Dangchang and Longxi, root length and diameter and weight of all the samples were measured. According to the clustering results, seedlings were divided into 3 levels, and field experiments were conducted with three levels seedling, yield and quality were tested in laboratory. Results have showed that emergence of grades 1 was faster than that of grades 2 and 3. Yield of grades 1 was significantly higher than that of grades 2 and 3 (P<0.05). Propargyl glycoside content of grades 1 was the highest, and significantly higher than that of grades 3. Polysaccharide content of grades 3 was the highest and significantly higher than that of grades 1 and 2 (P<0.05). So considering yield, quality and investment cost of C. pilosula, planting seedlings of C. pilosula should select that root length>15.6 cm, root diameter>2.7 mm, root weight>0.56 g.

The effects of phylogenetic relatedness on invasion success and impact: deconstructing Darwin's naturalisation conundrum.

Darwin's naturalisation conundrum describes the paradox that the relatedness of exotic species to native residents could either promote or hinder their success through opposing mechanisms: niche pre-adaptation or competitive interactions. Previous studies focusing on single snapshots of invasion patterns have provided support to both sides of the conundrum. Here, by examining invasion dynamics of 480 plots over 40 years, we show that exotic species more closely related to native species were more likely to enter, establish and dominate the resident communities, and that native residents more closely related to these successful exotics were more likely to go locally extinct. Therefore, non-random displacement of natives during invasion could weaken or even reverse the negative effects of exotic-native phylogenetic distances on invasion success. The scenario that exotics more closely related to native residents are more successful, but tend to eliminate their closely related natives, may help to reconcile the 150-year-old conundrum.

Biogeochemical processes governing natural pyrite oxidation and release of acid metalliferous drainage.

The oxidative dissolution of sulfide minerals (principally pyrite) is responsible for the majority of acid metalliferous drainage from mine sites, which represents a significant environmental problem worldwide. Understanding the complex biogeochemical processes governing natural pyrite oxidation is critical not only for solving this problem but also for understanding the industrial bioleaching of sulfide minerals. To this end, we conducted a simulated experiment of natural pyrite oxidative dissolution. Pyrosequencing analysis of the microbial community revealed a distinct succession across three stages. At the early stage, a newly proposed genus, Tumebacillus (which can use sodium thiosulfate and sulfite as the sole electron donors), dominated the microbial community. At the midstage, Alicyclobacillus (the fifth most abundant genus at the early stage) became the most dominant genus, whereas Tumebacillus was still ranked as the second most abundant. At the final stage, the microbial community was dominated by Ferroplasma (the tenth most abundant genus at the early stage). Our geochemical and mineralogical analyses indicated that exchangeable heavy metals increased as the oxidation progressed and that some secondary sulfate minerals (including jarosite and magnesiocopiapite) were formed at the final stage of the oxidation sequence. Additionally, we propose a comprehensive model of biogeochemical processes governing the oxidation of sulfide minerals.

Hidden diversity and potential ecological function of phosphorus acquisition genes in widespread terrestrial bacteriophages.

Phosphorus (P) limitation of ecosystem processes is widespread in terrestrial habitats. While a few auxiliary metabolic genes (AMGs) in bacteriophages from aquatic habitats are reported to have the potential to enhance P-acquisition ability of their hosts, little is known about the diversity and potential ecological function of P-acquisition genes encoded by terrestrial bacteriophages. Here, we analyze 333 soil metagenomes from five terrestrial habitat types across China and identify 75 viral operational taxonomic units (vOTUs) that encode 105 P-acquisition AMGs. These AMGs span 17 distinct functional genes involved in four primary processes of microbial P-acquisition. Among them, over 60% (11/17) have not been reported previously. We experimentally verify in-vitro enzymatic activities of two pyrophosphatases and one alkaline phosphatase encoded by P-acquisition vOTUs. Thirty-six percent of the 75 P-acquisition vOTUs are detectable in a published global topsoil metagenome dataset. Further analyses reveal that, under certain circumstances, the identified P-acquisition AMGs have a greater influence on soil P availability and are more dominant in soil metatranscriptomes than their corresponding bacterial genes. Overall, our results reinforce the necessity of incorporating viral contributions into biogeochemical P cycling.

Shifts in microbial community composition and function in the acidification of a lead/zinc mine tailings.

In an attempt to link the microbial community composition and function in mine tailings to the generation of acid mine drainage, we simultaneously explored the geochemistry and microbiology of six tailings collected from a lead/zinc mine, i.e. primary tailings (T1), slightly acidic tailings (T2), extremely acidic tailings (T3, T4 and T5) and orange-coloured oxidized tailings (T6). Geochemical results showed that the six tailings (from T1 to T6) likely represented sequential stages of the acidification process of the mine tailings. 16S rRNA pyrosequencing revealed a contrasting microbial composition between the six tailings: Proteobacteria-related sequences dominated T1-T3 with relative abundance ranging from 56 to 93%, whereas Ferroplasma-related sequences dominated T4-T6 with relative abundance ranging from 28 to 58%. Furthermore, metagenomic analysis of the microbial communities of T2 and T6 indicated that the genes encoding key enzymes for microbial carbon fixation, nitrogen fixation and sulfur oxidation in T2 were largely from Thiobacillus and Acidithiobacillus, Methylococcus capsulatus, and Thiobacillus denitrificans respectively; while those in T6 were mostly identified in Acidithiobacillus and Leptospirillum, Acidithiobacillus and Leptospirillum, and Acidithiobacillus respectively. The microbial communities in T2 and T6 harboured more genes suggesting diverse metabolic capacities for sulfur oxidation/heavy metal detoxification and tolerating low pH respectively.

[Effect of flavonoids from hedysari radix on pulmonary functions of pulmonary fibrosis rat].

OBJECTIVE: To study the effect of flavonoids from Hedysari Radix on pulmonary functions of pulmonary fibrosis rat and its mechanism. METHODS: 72 Wistar rats were randomly divided into 6 groups: blank control group, model group, prednisone group, Hedysari Radix flavonoids low, medium and high dosage group. The rat model was established by propelling bleomycin into bronchial tree through endotracheal intubation with laryngoscope. The pulmonary fanctions were measured. RESULTS: Hedysari Radix flavonoids could normalize the pulmonary functions of rats with bleomycin-induced pulmonary fibrosis. CONCLUSION: Hedysari Radix flavonoids can inhibit the process of pulmonary fibrosis.

Application of biochar and compost improved soil properties and enhanced plant growth in a Pb-Zn mine tailings soil.

This study evaluated the effect of biochar and compost on physiochemical properties, heavy metal content, microbial biomass, enzyme activities, and plant growth in Pb-Zn mine tailings. In this study, a pot experiment was conducted to evaluate the effects of biochar, compost, and their combination on the availability of heavy metals, physicochemical features, and enzyme activities in mining soil. Compared to separate addition, the combined application of biochar and compost was more effective to improve soil pH, soil organic carbon (SOC), total nitrogen (TN), available phosphorus (AP), and potassium (AK). All amendments significantly decreased CaCl2-extractable Pb, Zn, Cu, and Cd. Soil enzyme activities were activated by biochar and compost. Meanwhile, the addition of biochar and compost decreased heavy metal content in plant tissues and increased plant biomass. Pearson's correlation analysis showed that plant biomass was positively correlated with nutrient levels, microbial biomass, and enzyme activities, whereas it was negatively correlated with CaCl2-extractable heavy metals. These results enhance our understanding of the ecological functions of biochar and compost on the restoration of mining soil and reveal the potential benefit of organic amendments on the improvement of mining soil quality.

Phytostabilization mitigates antibiotic resistance gene enrichment in a copper mine tailings pond.

Mining-impacted environments are distributed globally and have become increasingly recognized as hotspots of antibiotic resistance genes (ARGs). However, there are currently no reports on treatment technologies to deal with such an important environmental problem. To narrow this knowledge gap, we implemented a phytostabilization project in an acidic copper mine tailings pond and employed metagenomics to explore ARG characteristics in the soil samples. Our results showed that phytostabilization decreased the total ARG abundance in 0-10 cm soil layer by 75 %, which was companied by a significant decrease in ARG mobility, and a significant increase in ARG diversity and microbial diversity. Phytostabilization was also found to drastically alter the ARG host composition and to significantly reduce the total abundance of virulence factor genes of ARG hosts. Soil nutrient status, heavy metal toxicity and SO42- concentration were important physicochemical factors to affect the total ARG abundance, while causal mediation analysis showed that their effects were largely mediated by the changes in ARG mobility and microbial diversity. The increase in ARG diversity associated with phytostabilization was mainly mediated by a small subgroup of ARG hosts, most of which could not be classified at the genus level and deserve further research in the future.

Diverse Methylmercury (MeHg) Producers and Degraders Inhabit Acid Mine Drainage Sediments, but Few Taxa Correlate with MeHg Accumulation.

Methylmercury (MeHg) is a notorious neurotoxin, and its production and degradation in the environment are mainly driven by microorganisms. A variety of microbial MeHg producers carrying the gene pair hgcAB and degraders carrying the merB gene have been separately reported in recent studies. However, surprisingly little attention has been paid to the simultaneous investigation of the diversities of microbial MeHg producers and degraders in a given habitat, and no studies have been performed to explore to what extent these two contrasting microbial groups correlate with MeHg accumulation in the habitat of interest. Here, we collected 86 acid mine drainage (AMD) sediments from an area spanning approximately 500,000 km2 in southern China and profiled the sediment-borne putative MeHg producers and degraders using genome-resolved metagenomics. 46 metagenome-assembled genomes (MAGs) containing hgcAB and 93 MAGs containing merB were obtained, including those from various taxa without previously known MeHg-metabolizing microorganisms. These diverse MeHg-metabolizing MAGs were formed largely via multiple independent horizontal gene transfer (HGT) events. The putative MeHg producers from Deltaproteobacteria and Firmicutes as well as MeHg degraders from Acidithiobacillia were closely correlated with MeHg accumulation in the sediments. Furthermore, these three taxa, in combination with two abiotic factors, explained over 60% of the variance in MeHg accumulation. Most of the members of these taxa were characterized by their metabolic potential for nitrogen fixation and copper tolerance. Overall, these findings improve our understanding of the ecology of MeHg-metabolizing microorganisms and likely have implications for the development of management strategies for the reduction of MeHg accumulation in the AMD sediments. IMPORTANCE Microorganisms are the main drivers of MeHg production and degradation in the environment. However, little attention has been paid to the simultaneous investigation of the diversities of microbial MeHg producers and degraders in a given habitat. We used genome-resolved metagenomics to reveal the vast phylogenetic and metabolic diversities of putative MeHg producers and degraders in AMD sediments. Our results show that the diversity of MeHg-metabolizing microorganisms (particularly MeHg degraders) in AMD sediments is much higher than was previously recognized. Via multiple linear regression analysis, we identified both microbial and abiotic factors affecting MeHg accumulation in AMD sediments. Despite their great diversity, only a few taxa of MeHg-metabolizing microorganisms were closely correlated with MeHg accumulation. This work underscores the importance of using genome-resolved metagenomics to survey MeHg-metabolizing microorganisms and provides a framework for the illumination of the microbial basis of MeHg accumulation via the characterization of physicochemical properties, MeHg-metabolizing microorganisms, and the correlations between them.

In situ enrichment of sulphate-reducing microbial communities with different carbon sources stimulating the acid mine drainage sediments.

The applications of sulphate-reducing microorganisms (SRMs) in acid mine drainage (AMD) treatment systems have received extensive attention due to their ability to reduce sulphate and stabilize metal(loid)s. Despite great phylogenetic diversity of SRMs, only a few have been used in AMD treatment bioreactors. In situ enrichment could be an efficient approach to select new effective SRMs for AMD treatment. Here, we performed in situ enrichment of SRMs in highly stratified AMD sediment cores using different kinds of carbon source mixture. The dsrAB (dissimilatory sulfite reductase) genes affiliated with nine phyla (two archaeal and seven bacterial phyla) and 26 genera were enriched. Remarkably, those genes affiliated with Aciduliprofundum and Vulcanisaeta were enriched in situ in AMD-related environments for the first time, and their relative abundances were negatively correlated with pH. Furthermore, 107 dsrAB-containing metagenome-assembled genomes (MAGs) were recovered from metagenomic datasets, with 14 phyla (two archaeal and 12 bacterial phyla) and 15 genera. The relative abundances of MAGs were positively correlated with total carbon and sulphate contents. Our findings expanded the diversity of SRMs that can be enriched in AMD sediment, and revealed the physiochemical properties that might affect the growth of SRMs, which provided guidance for AMD treatment bioreators.