零价铁对污泥高温厌氧消化过程中四环素抗性基因及第一类整合子的消减影响

Effect of Zero Valent Iron on the Decline of Tetracycline Resistance Genes and Class 1 Integrons During Thermophilic Anaerobic Digestion of Sludge

为研究污泥高温厌氧消化过程中零价铁(Fe0)对抗生素抗性基因的消减影响,采用荧光定量PCR方法定量检测了7种四环素抗性基因(TC-ARGs,包括tetA、tetC、tetG、tetM、tetO、tetW和tetX)及第一类整合子int I1基因在厌氧消化过程中的丰度变化,同时检测分析了挥发性脂肪酸(VFAs)的质量浓度变化,并探讨了目标基因与VFAs之间的相关关系.结果表明,适量Fe0(如0.10 g·g^(-1),以Fe0/VSS计)不仅可以强化污泥厌氧消化进程,显著提高总VFAs和乙酸的产生量,而且能够增强TCARGs和int I1基因的消减效果.尽管如此,过量Fe0(如1.17 g·g^(-1),以Fe0/VSS计)对污泥高温厌氧消化过程中TC-ARGs和int I1基因消减的增强效果并不显著,推测可能是由于基因水平转移的发生所导致的.通过相关性分析可知,TC-ARGs(除tetO基因外)和int I1基因与乙酸之间存在显著负相关性,表明乙酸可能对TC-ARGs和int I1基因的消减具有促进作用.

To investigate the effects of zero valent iron （Fe^0 ） on the decline of antibiotic resistance genes during thermophilic anaerobic digestion of sludge, the abundances of seven tetracycline resistance genes （TC-ARGs, including tetA, tetC, tetG, tetM, tetO, tetW, and tetX） and class 1 integron gene （intI1） were quantified by quantitative PCR （qPCR）. Also, the concentrations of volatile fatty acids （ⅤFAs） were determined. The correlations between the abundances of TC-ARGs and intI1 gene and the concentrations of ⅤFAs were discussed. The results showed that appropriate dose of Fe^0 such as 0. 10 g·g ^- 1 ⅤSS could enhance the anaerobic digestion process of sludge, and the production of total ⅤFAs and acetic acid increased significantly. The decrease in the abundances of TC-ARGs and intI1 gene was also enhanced. However, excessive Fe^0 such as 1. 17 g·g ^- 1 ⅤSS could not further improve the reduction in the abundances of TC-ARGs and intI1 gene, probably resulted from the occurrence of horizontal gene transfer. The abundances of TC-ARGs except tetO gene, as well as intI1 gene exhibited significant negative correlation with the concentration of acetic acid, indicating that acetic acid probably had an enhanced effect on the decline of TC-ARGs and intI1 gene during thermophilic anaerobic digestion of sludge.