Mechanisms On Effects Of Pharmaceutical Sewage Sludge Composting On Antibiotic Degradation And ARGs Transfer

China is one of the world's largest producers and consumers of antibiotics.With the development of the pharmaceutical industry,a large amount of pharmaceutical sludge has been produced.It will be able to develop and spread the antibiotics and antibiotic resistance genes?ARGs?into environment due to the improper disposal.The increasing prevalence of ARGs is a global threat to public health and environment.On the other hand,the demand for organic food products,especially for organic vegetables has been growing rapidly.However,the risk of introducing more ARGs and ABR to the vegetables by organic production has long been overlooked.This study was performed to analyze the effects of different types of sludge fertilizer from composting pharmaceutical sludge?Penicillin?on the abundance and diversity of ARGs in soil,root and phyllosphere of plants,in order to provide theoretical evidence for utilizing sewages sludge of penicilin.The key results of this study are summarized as following:?1?In order to investigate the changes of physico-chemical parameters such as temperature,organic matter and the degradation of penicillin during the one fermentation cycle of the composting system,different types of additional carbon sources or bamboo charcoal,bamboo charcoal or different carbon sources?glucose,sucrose and stalk powder?were added during pharmaceutical sludge composting.Results in this study indicated that the content of organic matter?OM?in mixed material was directly proportional to carbon sources,which also decreased with compost time and became consistent at the later stage.Thermal degradation might contribute to the degradation of penicillin during sludge composting.The dissolved organic carbon?DOC?and microbial utilization of carbon increased with the amended rates of carbon sources,which is due to the increase of microbial transformation and therefore increases the compost temperature.Adding carbon sources can facilitate the degradation rate of penicillin?the control group 94.44%in 15 days and more than 95%in the other groups?while the rate was the highest in the mixture of sucrose and cornstalk powder?within 15 days the degradation rate can reach 99.08%?.Penicillin content was negatively correlated with temperature?P?0.01?and dissolved organic carbon?P?0.01?during the warming phase?middle temperature stage and high temperature stage?in composting process.The degradation rate of penicillin could reach more than 90%within15 days in all treatments.And three kinds of sludge fertilizer were screened for further study.?2?The abundance and distribution of six reported?-lactamass genes(bla_-CTX-M-1,bla_-CMY,bla_-OXA-23,bla_-TEM,bla_-NDM-1NDM-1 and bla_CEP-02)were determined by PCR and qPCR,Isolation and analyzing?-lactamass genes(bla_-CTX-M-1,bla_-CMY,bla_-OXA-23,bla_-TEM,bla_-NDM-1NDM-1 and bla_CEP-02).The main results are as follow:the quantification of?-lactamass genes?bla_-CTX-M-1,bla-CMY,bla-OXA-23,bla-TEM,bla-NDM-1 and blaCEP-02?was decreased during aerobic composting,but the control of the diversity of ARGs and composting conditions during composting still requires further study.?3?Pot experiment was performed to explore the effects of sludge fertilizer application on the profile of ARGs in bulk soil,rhizosphere soil,root endophytes and phyllosphere of Brassica chinensis L.The results showed that the application of sludge fertilizer increased the abundance and diversity in bulk soil,rhizosphere soil,root endophytes and phyllosphere of Brassica chinensis L.Veen analysis demonstrated unique and shared ARGs in bulk soil,rhizosphere soil,root endophytes and phyllosphere,indicating that the soil after sludge fertilizer application is a major source of ARGs in phyllosphere.The analysis of Mantel test and Procrustes test were performed on shared Operational Taxonomic Units?OTUs?and ARGs in bulk soil,rhizosphere soil,root endophytes and phyllosphere of different treatments.Meanwhile,the shared OTUs had a significant influence on the composition of ARGs in phyllosphere.In summary,ARGs might transfer form sludge fertilizer to the surface of plants via rhizosphere using bacteria as medium.In the process,roots play a role as bridge.