零价铁对污泥厌氧消化过程中四环素抗性基因水平转移的作用影响

Effect of Zero Valent Iron on the Horizontal Gene Transfer of Tetracycline Resistance Genes During Anaerobic Sludge Digestion Process

细菌抗药性问题已成为全球生态环境安全和人体健康领域的一个关注焦点.污水处理剩余污泥是抗生素抗性基因(ARGs)的一个重要储存库和排放源,采用荧光定量PCR方法检测分析了四环素抗性基因(TC-ARGs,包括tet A、tet C、tet G、tet M、tet O、tet W和tet X)及第一类整合子int I1基因丰度在污泥厌氧消化过程中的变化特征,考察了不同投加量零价铁(Fe0)对目标基因的消长影响,初步分析了质粒DNA接合作用对TC-ARGs水平转移的作用影响,并探讨了TC-ARGs与int I1基因之间的相关关系.结果表明,污泥厌氧消化过程对TC-ARGs和int I1基因丰度具有不同程度的削减作用,其中tet X基因丰度降幅可达2.4个数量级.Fe0的加入对TC-ARGs和int I1基因丰度削减不显著,并且随着Fe0投加量的增加,TC-ARGs和int I1基因丰度相比对照组出现逐渐升高的趋势.通过对质粒组DNA所携带的TC-ARGs基因丰度进行检测分析发现,质粒DNA接合作用对TC-ARGs的水平转移具有促进作用.相关性分析结果显示,tet G与int I1基因之间具有显著正相关关系,表明int I1基因在污泥厌氧消化过程中可能对tet G基因的演变过程具有重要影响.

The problem of bacterial resistance has become an important issue in the area of global ecological safety and human health.Waste sludge is an important reservoir and discharge source for antibiotic resistance genes（ ARGs）. In this study,the quantities of seven tetracycline resistance genes（ TC-ARGs）,including tet A,tet C,tet G,tet M,tet O,tet W,and tet X,as well as those of class 1 integron（ int I1） genes,during anaerobic sludge digestion process were comprehensively quantified by quantitative PCR（ q PCR）. The effects of different doses of zero valent iron（ Fe0） on the decrease and increase in the quantities of TC-ARGs and int I1 genes were investigated. The influence of plasmid conjugation on the horizontal gene transfer（ HGT） of the target TC-ARGs was preliminarily analyzed. The correlations between the quantities of TC-ARGs and int I1 gene have been discussed. The results showed that the quantities of TC-ARGs and int I1 genes decreased in different degrees during anaerobic sludge digestion,and the abundance of tet X gene was reduced by 2. 4 orders of magnitude. When Fe0 was added,no significant reduction in the quantities of TC-ARGs and int I1 genes was observed. However,as the addition of Fe0 increased,the quantities of TC-ARGs and int I1 genes increased correspondingly,as compared to those in the control group. The results obtained from the quantities of TC-ARGs carried by plasmid DNA showed that plasmid conjugation probably promoted the HGT of TC-ARGs. A positive significant correlation was found between the quantities of tet G and int I1 genes,indicating that int I1 might play an important role in the evolution of tet G during sludge anaerobic digestion process.