Distribution And Occurrence Mechanism Of Antibiotic Resistance Genes In High-Water-Level Agricultural And Fishery Reclaimed Mining Area

In recent years,the problem of antibiotic resistance pollution has attracted the attention of experts and scholars,especially the high metal levels in the mining environment aggravate the occurrence and spread of new pollutants,antibiotic resistance genes(ARGs).This study pays attention to the shallow groundwater buried in the high-water-level mining area,and a large area of water accumulation is formed after the collapse,so the agricultural and fishery reclamation are carried out according to local conditions.The import of antibiotics from agricultural and fishery activities may aggravate the pollution of ARGs,but its distribution pattern and occurrence mechanism are still unclear.In this thesis,the occurrence characteristics of ARGs in agricultural and fishery reclaimed soils in subsidence areas of high-water-level mining areas were studied.Detecting the species,relative abundance of ARGs and microbial community structure in reclaimed soil by metagenomics.The physical and chemical properties and metal element of reclaimed soil were studied,and the key factors affecting the occurrence of ARGs in reclaimed soil were explored.Since reclaimed soil has a unique mechanism of sediment backfilling,this study examined the ARGs abundance and microbial community structure in the sediments of reclaimed fishing ponds to explore its effects on ARGs and microbial community structure in reclaimed soil.The environmental characteristics of high sulfur are the most critical influencing factors in this study.Through the analysis of sulfur metabolism-related genes and microorganisms,the mechanism of sulfur-driven ARGs occurrence in soil was explored.The main research results are as follows.(1)A total of 957 ARGs were detected in soil samples,and mac B was the most widely distributed resistant gene in reclaimed soil.Multidrug ARGs were the most widely distributed resistant gene subtypes,and the efflux pump mechanism was the main resistant mechanism of ARGs in soil.The reclaimed soil showed higher ARGs storage capacity than the control soil.The relative abundances of most ARGs and ARGs subtypes increased with the depth of reclaimed soil.ARGs showed the ability to migrate vertically to deeper soil and accumulate.The microbial structures of the reclaimed soil and the control soil were significantly different.Proteobacteria was the most dominant bacterial phylum in reclaimed soil.Through correlation analysis and contribution analysis,it was determined that Proteobacteria,Actinobacteria,Acidobacteria,Gemmatimonadetes and Chloroflexi were the main antibiotic resistance bacteria(ARB).(2)The soil samples in the study area were all weakly alkaline.The contents of environmental factors such as total carbon,organic matter,total nitrogen and total phosphorus in the control soil were higher than those in the reclaimed soil.The soil has a certain degree of accumulation of heavy metal,which has a certain positive impact on the occurrence of ARGs in the soil.Total sulfur(TS)was the most different environmental characteristic between the reclaimed soil and the control soil in this study.TS was positively correlated with the dominant ARGs.In addition,TS was positively correlated with dominant microbial phyla in soil,including major ARB such as Proteobacteria,Acidobacteria,and Gemmatimonadetes.TS has a significant impact on the microbial community structure in reclaimed soil,so sulfur is the most critical factor driving the occurrence of soil ARGs in this study.(3)The investigation of ARGs in the sediments of reclaimed fishing ponds showed that the most abundant mac B and multidrug ARGs in the reclaimed soil accounted for a large proportion in the sediments.In addition,seven of the ten ARGs with the highest relative abundance in the reclaimed soil were present in the sediments.Therefore,the ARGs present in the sediment after backfilling may enter the reclaimed soil.Proteobacteria was the most dominant microbial phylum in the sediments,which was the same as that of reclaimed soils.Proteobacteria was also the most important ARB in the sediments.Sediment backfill is likely to affect the microbial community structure of reclaimed soils.These results also indicate that backfill sediments are one of the potential sources of ARGs in reclamied soils.The high-sulfur ecological environment caused the relative abundance of sulfur metabolism functional genes in the reclaimed soil to be higher than that in the control soil.High levels of sulfur metabolizing capacity may have promoted the proliferation of microbial populations in reclaimed soils.In addition,sulfur led to the proliferation of sulfur metabolizing microorganisms such as Proteobacteria,Acidobacteria,Gemmatimonadetes,Chloroflexi and Rokubacteria in the reclaimed soil.This may be the main reason for the difference in microbial structure between it and the control soil.Meanwhile,these sulfur metabolizing microorganisms are the main ARB in reclaimed soil.Therefore,the massive proliferation of these microbial phyla created conditions for the vertical transfer of ARGs.TS increased with the depth of reclaimed soil,which was probably the main reason for the abundant ARGs in deep soil.Sulfur drives the occurrence of ARGs in reclaimed soil by affecting microbial community structure.