Antibiotics In The Soil-vegetable System Composted With Livestock Manure Study On The Spread Characteristics Of Antibiotics And Antibiotic Resistance Genes

In recent years,the widespread application of farmyard manure has not only brought a lot of antibiotic soil pollution,but the antibiotic resistance genes(ARGs),it carries will also enter the soil ecological environment.ARGs in the soil can threaten human health through the food chain.Aerobic composting is generally considered to be an economically feasible and environmentally friendly technology that can effectively prevent the diffusion of ARGs and ARBs from fertilizer to farmland soil.There have been a lot of studies on the changes of manure-derived antibiotics and ARGs after composting.However,the distribution characteristics of ARGs at different interfaces of the plant-soil system after applying manure at different maturity stages are still unclear.For different types of soil-vegetable systems(leaf vegetable Plants and tubers),the differences between the two also need to be explored.Therefore,the purpose of this study is to use potted plant experiments to take leafy vegetables(Shanghai green)and tubers(carrots)as examples.The purpose is to study the effects of composting livestock and poultry manure at different maturity stages on different types of plant-soil systems.The influence of bacterial communities;on this basis,the migration and distribution of antibiotics and their resistance genes in different types of soil-vegetable systems are studied from the three interfaces of vegetable roots,rhizosphere soil and non-rhizosphere soil,to explore antibiotics and their resistance.The spread of genes in different plant-soil systems,and explore the relationship between antibiotics,ARGs,and bacterial communities.The main research conclusions of the thesis are as follows:(1)Composting can effectively reduce antibiotics and ARGs in pig manure.The absolute abundance of resistance genes in the compost samples showed a trend of Trgs >SRGs>QRGs.For one gene encoding pump efflux mechanism(tet G)and one gene encoding enzyme inactivation mechanism(tet X),the reduction effect was not obvious.Both TRGs and SRGs showed a trend of first increasing and then decreasing,while qnr S continued to decrease in the whole composting process;(2)Composting can effectively reduce ARGs from feces into soil-vegetable system,and the higher the ripening degree,the less the ARGs are introduced.Compared with commercial manure,the abundance of ARGs introduced into soil-vegetable system by laboratory compost was relatively lower;(3)(3)Both leafy vegetables and tubers significantly reduced the abundance of ARGs introduced by manure into soil;The distribution of total abundance of ARGs in different soil-vegetable systems showed a general trend in the three interfaces: rhizosphere soil >non-rhizosphere soil > roots,and only one QRGs(qnr S)were distributed as follows:roots> rhizosphere soil > non-rhizosphere soil;The total abundance of ARGs in leaf vegetable plant-soil system was significantly higher than that in tuber plant-soil system;(4)Enzyme inactivation mechanism(tet X)is the main mechanism of tetracycline resistance in soil-vegetables.The abundance of tet A,tet C and tet G were significantly higher in tuber plant-soil system than in leaf vegetable plant-soil system,while the abundance of tet X and sul1,sul2 and qnr S genes were just the opposite;(5)Plant types have great influence on the composition of bacterial community in soil.On the whole,the higher the degree of maturation of manure,the smaller the change of soil microbial community diversity,the change of soil microbial community of commercial manure was significantly different from that of laboratory compost;(6)Network analysis showed that Proteobacteria,Actinobacillus and Firmicutes were the main host bacteria of ARGs in soil,including four potential pathogenic bacteria(Bacillus,Acinetobacter,Mycobacterium and Staphylococcus).There was a significant positive correlation between tet A,tet G,tet X,sul2 and qnr S and potential pathogenic bacteria(P < 0.05).In summary,in the different types of plant-soil systems using livestock manure compost at different maturity stages,compared with commercially available manure,the abundance of ARGs introduced into different types of plant-soil systems in laboratory compost is relatively low;the higher the degree of maturation The less abundance of ARGs introduced by fertilizers;leafy vegetables and tubers can reduce the antibiotics and ARGs in the rhizosphere soil,so these plants can be used to reduce the antibiotics and ARGs in the soil.The total abundance of ARGs in the leaf area of leafy vegetables is significantly higher than that of tuber plants,and even higher than that of root endophytes.As the edible part of leafy vegetables,the leaf area has a higher risk.Plants reduce the abundance of ARGs by reducing the abundance of Firmicutes,which provides a new idea for studying the reduction of ARGs in soil.