Effects Of Livestock Manure Or Sewage On Soil Microbial Community And Antibiotic Resistance Genes In Farms

The overuse of antibiotics induced the production of antibiotic resistance genes(ARGs)in microorganism,which accelerated the spread of resistant bacteria and antibiotic resistance genes in the environment and posed a serious threat to public health and the ecological environment.At present,antibiotic resistance genes,a new kind of environmental pollutants,can not only be widely spread by means of various media,but also shift among microorganisms through horizontal gene transfer.The environmental risk of antibiotic resistance genes was much higher than that of antibiotics.Currently,livestock manure and domestic sewage had attracted widespread concern because they were rich in antibiotic resistance genes.Based on 16 S rDNA high-throughput sequencing technology and quantitative PCR technology,an experiment was conduncted by adding the manure,sewage and tap water respectively in different soil to evaluate the effect of different factors on bacterial community structure and ARGs abundance.Co-occurrence networks was used to analyze the interactions among bacterial communities and ARGs and the potential host bacteria.The main results and conclusions are as follows:On the one hand,we concluded that there was little change in species richness and composition in soil with different treatments.In BZ or YL soils,the difference in community structure between different treatments was extremely significant,while the community differences among different treatments in JX soil were slightly significant.Therefore,it could be explained that the effects of different treatments on the microbial community structure of different soils were different.With the increase of processing time,the alpha diversity and beta diversity in BZ or YL soil showed a slow increase,whereas they changed less in JX soil.Variance analysis showed that there was a significant difference in soil bacterial community structure with processing time,which explained 5.7% of community variation.In addition,there was a significant difference in bacterial community between the wheat-planted and non-planted wheat samples.Alpha diversity in JX and YL soils grown with wheat was significantly higher than in unplanted wheat,but the opposite trend was observed in BZ soil.Moreover,dominant species such as Proteobacter,Actinobacteria,and Bacteroides had higher abundance in wheat-growing soil than those without wheat.On the other hand,we detected higher abundance of ARGs in the manure(M)and sewage(S)samples than the control soil by fluorescence quantitative PCR,and the copies of five ARGs and intI1 in sewage(S)samples were 8 to 10 times higher than those in compost(M).The practice of reusing compost and sewage for agricultural fertilization significantly increased the number of copies of ARGs in soil,and the tetracycline resistance gene tetX had the highest abundance.Howere,the ARGs abundance in the soil gradually decreases with the increase of processing time.The ARGs abundance in soil grown with wheat is much lower than soil without wheat.The Network analysis demonstrated that Proteobacteria,Actinobacteria,Acidobacteria and Bacteroidetes were dominated microorganisms at phylum level contributing for the change of ARGs abundance.At the genus level,a total of 59 bacterial genera showed significant correlations with ARGs,mainly in the one-to-one and one-to-many interactions.We speculated that ARGs not only have their own independent associated host,but also share the same host with other genes.This study revealed the difference in microbial communities and antibiotic resistance genes in different soils treated with manure,sewage,and tap water,and analysed the significant correlation among them and the potential host bacteria of ARGs.This conclusion provided theoretical support for understanding and assessing the environmental effects of manure and wastewater reuse.