Effects Of Swine Manure Composting On ARGs And The Initial Research Of Changes Of Microorganism Community

Frequent abuse of antibiotics in the livestock industry accounted for a large proportion of the world production of antibiotics, and most proportion of antibiotics are excreted in the form of their parent compounds or metabolites via urine and faces. This could cause the presentation of antibiotic-resistant strains (antibiotic resistance bacteria, ARB) and antibiotic resistance gene (ARGs) by environment selective pressure from antibiotics of manure. The manure contained antibiotics, ARB and ARGs would influence the surrounding farmland soils and make further diffusion and transfer in the environment, which might pose the potential threat on environmental microbial community structure and human health systems. Tetracycline, sulfonamides, macrolides, ?-lactams and quinolones are the most widely used antibiotics in livestock industry, so the problem of their corresponding resistance genes was more severe. Currently, research on ARGs contaminated mostly focused on the abundance detection of soil, water and their ecological effects. However, few studies focused on the ARGs during composting process and manure composting products, so it is much more necessary to explore their ecological risk.In this study, sawdust was mixed with swine manure(SS pile) and tea residues were mixed with swine manure (ST pile) made windrow composting. The quantitative PCR method was used for detecting the abundance of five typical ARGs during composting process. And method of PLFA was used for preliminarily analyzing the microorganism community structure during the composting process. By comparing the effects of two bulking agents on ARGs, physiochemical indicators and microorganism community structure, the two bulking agents were only as regulators of carbon and nitrogen and there were no significant effect (P> 0.05). The quantitative PCR results showed that different types of ARGs in the composting process had different fates. Most of ARGs were reduced during the composting process. During the SS and ST piles composting, the behaviors of ARGs were as follows:TetB removal rate are 99.2%,99.3%; tetM removal rate are 97.8%,99.0%; tetK removal rate are 97.2%,97.3%; tetZ removal rate are 64.8%,78.4%; tetS removal rate are 99.4%,99.5%; tetT removal rate are 95.7%,95.4%; tetQ removal rate are 99.1%,97.9%; tetH removal rate are 75.8%,84.1%; tetO removal rate are 99.1%,99.1%; but some ARGs, such as resistance genes tetA, tetC, tetY, tetG and other tetracycline antibiotic resistance genes, sull, sul2, ermF and qnrA occurred proliferation or the according to the initial value. TetA increased 5.6-fold, 2.9-fold; tetC increased 7.6-fold,1.5-fold; tetY increased 1.2-fold,3.5-fold; tetG increased 2.7-fold,2.9-fold; sull increased 2.1-fold,1.1-fold; sul2 increased 5.7-fold,1.6-fold; ermF increased 3.2-fold,0.4-fold; qnr would remain essentially the same.These results indicated that thermophilic composting process cannot effectively remove all ARGs. For some ARGs, compost may be a good bioreactor resulting in their proliferation. Application of composting products on farmland may cause transference of ARGs. And these findings deepened the understanding of the way of spread of ARGs in the environment and provide important theoretical basis to study of blocking mechanism of ARGs.