| With the exploitation of antimony(Sb)mineral resources and the wide application of Sb,antimony pollution has become increasingly prominent ecological and environmental issues.Physical,chemical,and biological processes,as well as the interaction between surface water and groundwater,affect the migration and transformation of antimony in nature.Therefore,antimony pollution usually presents a three-dimensional distribution pattern in the mining area.However,due to the different emphasis in different subjects,the research on the biogeochemical cycle of antimony in context of interation of above ground and underground systems is stilllimited.This situation seriously restricts our understanding of the interaction between microorganisms and Sb in mining area.Moreover,the impact of antimony on underground ecosystem under different hydrological conditions is also sparely studied to date.In the context of global warming and extreme rainfall events in high frequency,the interaction between aboveground and underground ecosystems and the ecological consesquence would be more intense and may show significant impact on ecosystems.Therefore,it is of great significance to link the aboveground and underground ecosystem at mining area to reveal the migration,transformation,and impact of Sb on ecosystem.Bases on this idea,the research results obtained in this study will greatly enhance our understanding of the biogeochemical cycle of antimony and provides a new window to deal with the antimony pollution in mining area.Under the guidance of the interaction of aboveground and underground ecosystem in mining area,this paper focuses on the following aspect including the microbial community in groundwater,the molecular mechanism of the interaction between microorganisms and antimony,and the interaction between microorganisms and antimony bearing minerals at the community level.Samples were collected from the North Xikuangshan(XKS)Sb mine in Lengshuijiang City of Hunan Province,which subjected to microbial communities and their interaction with antimony-bearing minerals via high throughput sequencing,faprotax functional gene prediction,co-occurrence network,Sloan random model fitting,microbial enrichment community and single bacteria screening culture,fluorescence spectrum analysis,XRD mineral analysis,whole genome analysis,comparative genome,and pan genome analysis.The main achievements are as follows:(1)Characteristics and environmental driving mechanism of microbial communities in Sb-bearing solid waste from Xikuabgshan mines.Microbial communities in Sb-containing solid waste were dominated by Proteobacteria and Actinobacteria at the phulum level,and Thiobacillus,Hydrogenophaga,Lysobacter,Dechloromonas and Novosphingobium at the genus level.The diversity and composition of microbial communities significantly varied in different types of antimony containing solid wastes.Overall,the concentrations of Sb and NO3~-significantly controlled the microbial community structure as indicated by RDA analysis.The concentration of Sb showed most serious impat on the microbial community of conditionally rare taxa.Rare taxa contributed most to the microbial diversity in the Sb containing solid waste.Microbial groups cooperated with each other to survive in Sb-bearing solid waste as indicated by the cooccurence network.Bacterial community assembly was dominated by randomness.(2)Heavy rain event significantly changed the composition,potential function,and interaction of groundwater microbial communities in Xikuangshan mine.Moreover,the neutral theory played a vital role in the construction of bacterial community assembly in groundwater.Heavy rain event(HRE)strongly shifted the composition,potential function of microbial community and the interaction between different microbial groups.At the same time,it destroyed the interaction between microorganisms and reduced the stability of groundwater microbial network.Concentration of Sb is always the fundamental environmental variable which controlled microbial communities in groundwater at XKS despite of the weakened impact of Sb during HRE.Like the observation found in microbial communities in Sb-bearing solid waste,rare taxa in microbial communities in dry period(DP)was more impacted by Sb concentration than other microbial groups.On the contrast,Eh significantly impacted on rare taxa in microbial communities in groundwater during HRE and strongly shaped the overall microbial communities in HRE.The ecological processes in microbial assembly of groundwater are generally limited by dispersal rate and is more likely to be affected by the environmental conditions.Groundwater microbial community aeembly was dominated by stochastic process.However,the ecological processes underling the community construction were different under different rainfall conditions.Stochastic processes contributed more to community assembly in HRE.(3)Genome sequencing of Paraccocus versutus XT0.6 confirmed the Sb(V)detoxification mechanism and the presence of Sb oxidizing genes such as aio AB.Moreover,P.versutus showed an open pan-genome,indicating a strong ability to obtain genes from outside.These results were of great significance to further understand the molecular mechanism of Sb metabolism.In addition to the reported population of antimony oxidizing bacteria,48 Sb oxidizing bacterial strains were isolated from various environmental samples at Xikuangshan mining area,indicating that a large number of known species of microorganisms may have potential to involve in Sb oxidization.The strain XT0.6 with high antimony oxidation capability and strong resistance to Sb belongs to Paraccocus versutus of?-Proteobacteria.XT0.6 could oxidize Sb efficiently both anaerobically and aerobically.Besides that,XT0.6 is also capbale of arsenic reduction.Genome sequencing showed that XT0.6 contained double chromosomes with Sb(V)detoxification mechanism from Pet to ABC transporter,complete ars operon,Sb oxidation genes such as aio AB,Sb resistance related genes and heavy metal resistance genes.At the same time,the strain XT0.6 contained a large number of genes with unknown functions(such as SDR family),which are likely to participate in the Sb oxidation process.P.versutus had an open pan-genome and a strong ability to obtain genes from the outside world.The core genome of P.versutus contains the same functional genes of arsenic and antimony metabolism and heavy metal resistance as the strain XT0.6 had.However,strain XT0.6 had more copies of these genes and the evolutionary distances of these genes were different,which indicated strain XT0.6 may obtain Sb oxidation capacity and other heavy metal metabolism capacity via horizontal gene transfer.(4)Microbial community played a significant role in the geochemical cycle of Sb release,oxidation and coprecipitation.A large number of microorganisms related to antimony oxidation,including the antimony oxidizing strains isolated in this study was detected in bacterial communities interacting with stibnite.Moreover,the release and oxidation of antimony were positively correlated with the relative abundances of Paracoccus and other microbial groups capable of antimony oxidation,further confirmed microbial participation in the biochemical cycle of antimony in the environment.Due to the environmental stress resulting from Sb release,different microbial populations showed cooperative interaction with each other during the process of the interaction of microbial communities and antimony-bearing mineral.Microbial communities significantly impacted on the release and oxidation of stibnite under different environmental conditions.Correspondingly the microbial community structure succeeded with the antimony release,oxidation and redepositon in the system.Microbial degradation of organic matter is enhanced under conditions with relatively simple nutrients,which subsequently favor for the dissolution of stibnite.With the presence of microbial communities,p H was not the sole determinat factor controlling the release of Sb from stibnite.Moreover,the precipitation of Sb(V)was only detected in microbial inoculated systems.All these confirmed that microbial community plays an irreplaceable role in the geochemical cycle of antimonyThe innovation of this paper is as follows:(1)This study firstly demonstrated the impact of extreme rainfall events on groundwater microbial communities in Sb mining area,shifting microbial communities,potential functions,and microbial interactions.(2)Gemome sequencing of XT0.6 confirmed the presence of Sb(V)detoxification and Sb(?)oxidizing gene.Moreover XT0.6 may aslo obtain genes via horizontiaonl gene transfer. |
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