| In recent years,the contamination of antibiotics and antibiotic resistance genes?ARGs?in water environment is increasingly intensified due to the extensive use of antibiotics.The distribution and transmission mechanism of antibiotics and antibiotic resistance genes in water environment has become a common concern in the world.As one of the most important water resources on earth,lakes are closely related to the survival,reproduction and development of human beings.Most of the studies was focused on central and eastern lakes,however,the study on typical salt lakes in the arid regions of northwest China was limited.In this study,surface water and sediment samples from Ebinur Lake and two inflow rivers were collected in winter and summer to detect antibiotics,antibiotic resistance genes and microbial communities.The spatial and temporal differentiation of antibiotic and antibiotic resistance genes and their correlation with major environmental factors,the composition and structure of the microbial community in the sediments and its response to the contamination of antibiotic and antibiotic resistance genes in the Ebinur Lake Basin were studied systematically,combined with laboratory microbial culture experiment.The main results obtained were summarized as follows:?1?The concentrations of 12 antibiotics of 4 major classes in surface water and sediments in Ebinur Lake Basin were generally at ng/L level.The concentration of antibiotics was higher in winter than in summer.In winter,the total concentration of antibiotics in surface water ranged from 46.03 to 465.80 ng/L,and the average concentration was 189.40 ng/L.Macrolide antibiotics?52.5%?accounted for the highest proportion.The pollution generally showed the pattern of Jing River>Bortala River>Ebinur Lake.In summer,the total concentration of antibiotics in surface water ranged from 26.94 to 537.17 ng/L,and the average concentration was103.97 ng/L.The sulfonamides antibiotics?63.4%?accounted for the highest proportion,and the pollution generally showed the pattern of Ebinur Lake>Bortala River>Jing River.The total concentration of antibiotics in the sediments ranged from 1.65 to 92.68 ng/g,with an average concentration of 27.38 ng/g in winter.The total concentration of antibiotics in the sediments in summer ranged from 7.72 to 22.46 ng/g,and the average concentration was 13.34 ng/g.In the sediments,macrolide antibiotics?52.2%?were the main antibiotics in winter,and quinolones?60.2%?were the main antibiotics in summer.The overall contamination of antibiotics was the pattern of Jing River>Bortala River>Ebinur Lake.The results of risk quotients method showed that SMX and OFL in surface water of Ebinur Lake Basin have high environmental risks.?2?Sulfonamide resistance gene?sul1,sul2?,macrolide resistance gene?ermB?,tetracycline resistance gene?tetW?,quinolone resistance gene?qnrS?and integron int1 were detected in Ebinur Lake Basin.The relative abundance of ARGs in surface water ranged from 10-1 to 10-5copies/16S rRNA in winter and 10-1 to 10-2 copies/16S rRNA in summer.The general trend of relative abundance of ARGs in winter and summer is the same:sul1>int1>sul2>tetW>ermB>qnrS.The relative abundance of ARGs in sediments ranged from 10-2 to 10-5 copies/16S rRNA.The relative abundance of ARGs in winter is sul1>int1>sul2>tetW>ermB>qnrS and in summer is sul1>sul2>int1>tetW>ermB>qnrS.Two sulfonamine-resistance genes,sul1 and sul2,showed significant positive correlation with integron int1 in sediments,indicating that the strong horizontal gene transfer of sulfonamides resistance genes.?3?The diversity and richness of microbial community in the sediments of Ebinur Lake Basin have obvious seasonal and spatial changes.and the diversity and richness of microbial community in sediments from the rivers into the lake were higher in summer than in winter,while the contrary is found in Ebinur Lake.Proteobacteria dominated the composition of the microbial community in the sediments of the rivers,and Chloroflexi dominated the composition of the microbial community in the lake.The conductivity was a key environmental factor affecting the differences of the microbial community between the rivers and the Ebinur Lake.?4?The macrolides,tetracyclines and quinolones antibiotics were positively correlated with Patescibacteria and Bacteroidetes,and negatively correlated with Gemmatimonadetes.Sulfonamides antibiotics were only negatively correlated with Firmicutes and positively correlated with Chloroflexi.Network analysis showed that sulfonamine-resistant genes contained65 potential host bacteria,and 16 bacteria genera including Phenylobacterium,Zoogloea,Pedobacter and Nitrospira might be potential host bacteria of both int1 and sul1.?5?Laboratory experiments showed that the increase of salinity would reduce the diversity of microbial community in sediments.The pollution of sulfamethoxazole would further reduce the diversity of microbial community,especially under high salinity conditions.However,the richness of the microbial community was not obvious in response to the salinity,and sulfamethoxazole may act as a carbon source to promote the reproduction of microorganisms and increase the richness of the microbial community.Firmicutes and Proteobacteria were the dominant bacteria.Bacillus and Thalassobacillus are the dominant bacteria in high salinity.Sulfamethoxazole contamination under salt stress affected microbial membrane transport and other functional genes. |
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