牛粪发酵过程中抗生素耐药基因及相关菌群组成变化规律

随着规模化奶牛养殖迅速发展,牛粪带来的环境污染问题日益严重。实验探究牛粪及其堆肥过程中养分变化、抗生素耐药基因消减情况以及细菌群落演替规律,探讨细菌菌群与养分、抗生素耐药基因之间的相关性。采集牛粪及其堆肥过程样品,测定样品中养分、检测抗生素耐药基因相对丰度,采用16S rRNA高通量测序技术研究牛粪堆肥过程细菌群落变化。结果表明,从新鲜牛粪(组FM)到发酵牛粪(组C),样品中有机质含量下降,全氮和全磷含量有不同程度增加,全钾(TK)显著升高(P<0.05)。堆肥发酵后,抗生素耐药基因erm B、tet M、bla CTX-M和aac(6′)-Ib-cr的相对丰度呈现不同程度的下降,而基因sul 1相对丰度增加。高通量测序结果表明,在门水平,各组均以Firmicutes、Proteobacteria和Bacteroidetes这3个菌门为主,在属水平,各组具有不同的优势物种,其中发现Bacteroides、Paeniclostridium和Pseudomonas等7个潜在病原菌属的相对丰度在堆肥后有效降低。通过相关性分析发现,潜在病原菌属与基因tet M和sul 1呈显著正相关(P<0.05),此外,大部分优势菌属与养分TK有显著相关性(P<0.05)。研究结果表明,牛粪经堆肥发酵后,病原菌相对丰度有效降低,抗生素耐药基因相对丰度的下降与细菌菌群结构变化存在相关关系。

Change of Antibiotic Resistance Genes and Bacterial Communities during Dairy Manure Composting Process

Environmental pollution caused by manure which was generated from intensive dairy farm has become an increasingly serious problem. Therefore, this study investigated the dynamics of nutrients, antibiotic resistance genes (ARGs) and bacterial communities during dairy manure composting to find the correlations between them. Samples of fresh dairy manure (FM), pretreatment manure (PM) and its composts (C) were collected, and the nutrients and ARGs were determined. The dynamic of bacterial community was analyzed by using 16S rRNA high-throughput sequencing. After composting, the content of total nitrogen, phosphorus and potassium (P<0.05) increased, but organic matter decreased. The abundance of aac(6'')-Ib-cr, blaCTX-M, tetM (P<0.05) and ermB (P<0.05) genes decreased after composting, but that of the sul1 gene increased. The results showed that the phyla of Firmicutes, Proteobacteria and Bacteroidetes were dominant in all groups. However, each group has different dominant species at genus level. Interestingly, all potential pathogens reduced after composting. The correlation analysis revealed that certain potential pathogens were significantly correlated with tetM and sul1 genes (P<0.05). Besides, most dominant genera were significantly correlated with total potassium (P<0.05). In conclusion, the change of bacterial community structure along with the composting may lead to the decrease of pathogens and ARGs in dairy manure.