鸡粪-堆肥中重金属残留、抗生素耐药基因及细菌群落变化研究

研究鸡粪及其堆肥过程中养分变化、重金属残留、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、重金属、抗生素耐药基因之间的相关性。采集鸡粪及其堆肥过程样品,测定样品中养分、重金属含量,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鸡粪堆肥过程细菌群落变化。从鲜鸡粪(组FM)到二次发酵(组SC),样品中有机质含量下降,全氮和全磷含量有不同程度增加,全钾及pH值显著升高(P0.05)。重金属在不同组中的浓度呈波动变化,与组FM相比,在组SC中砷(As)、镉(Cd)浓度升高,铜(Cu)、锰(Mn)、铅(Pb)浓度下降,其中锌(Zn)下降显著(P0.05)。堆肥后,抗生素耐药基因aac(6′)-Ib-cr、tet M(P0.05)、erm B(P0.05)和bla CTX-M(P0.05)的相对丰度呈现不同程度的下降,而基因sul1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 3个菌门为主。在属水平,各组具有不同的优势物种,同时潜在病原菌属的相对丰度均随堆肥过程降低。通过相关性分析发现,大部分优势菌属与全磷、pH值、重金属Cr及耐药基因sul1、tet M、erm B和bla CTX-M有显著相关性(P0.05)。鸡粪经堆肥后可降低病原菌及抗生素耐药基因相对丰度,但仍存在一定风险,该研究可为实际生产中鸡粪的高效、安全堆肥处理提供参考。

Dynamics of heavy metal residues, antibiotic resistance genes, and bacterial communities during chicken manure composting

The changes in the content of nutrients and heavy metals, abundance of antibiotic resistance genes (ARGs), and the succession law of bacterial communities were investigated during chicken manure composting to explain the correlations between bacterial communities and nutrients, heavy metals, and ARGs. Fresh chicken manure (FM)and its compost samples (FC and SC)were collected, and their nutrient and heavy metal content, and the abundance of ARGs were determined. The succession law of bacterial community was analyzed by 16S rRNA high-throughput sequencing. After composting, the content of organic matter decreased, but the content of total nitrogen and phosphorus increased at different levels, whereas, the total potassium content and pH significantly increased (P<0.05). The heavy metal content fluctuated in different sample groups. Compared with those in FM, the concentration of arsenic and cadmium increased in SC,whereas the content of copper, manganese, lead, and zinc (Zn)decreased in SC; only the concentration of Zn decreased significantly (P< 0.05). The abundance of the ARGs aac (6'')-Ib-cr, tetM (P<0.05), ermB (P<0.05), and blaCTX-M decreased (P<0.05)at different levels after composting, but the abundance of the gene sul1 increased. The results showed that the phyla Firmicutes, Proteobacteria, and Bacteroidetes were dominant in all the groups. However, each group had different dominant species at the genus level, and the abundance of potential pathogens reduced during composting. The correlation analysis revealed that the most dominant genera significantly correlated with the content of total phosphorus and Cr, pH, and abundance of the ARGs sul1, tetM, ermB, and blaCTX-M (P<0.05). The relative abundance of pathogens and ARGs can decrease after composting, but there are still some risks. This study provides a reference for efficient and safe composting treatment of chicken manure during actual production.