厌氧和好氧处理过程中四环素抗药基因的丰度

为了了解抗生素生产废水不同处理过程(厌氧生物处理和好氧生物处理)中抗药基因的行为,本文以两种四环素(土霉素、金霉素)生产废水处理系统为调查对象,采用PCR和实时定量PCR(qPCR)方法考察厌氧和好氧处理过程中常见的6种四环素抗药基因(tet(A), tet(C), tet(G), tet(Q), tet(W), tet(X))及2种转移因子(I型整合子intI1, 异常插入序列ISCR3)的丰度特征.结果表明,tet(C)在所有样品中均未检出,其它基因在所有样品中检出.四环素生产废水处理系统中,厌氧污泥中tet(A)、tet(G)、tet(X)的相对丰度(与16S rRNA基因的比值)范围为(1.25±0.16)×10^-4~(4.52±0.002)×10^-2,显著低于好氧污泥(9.88±0.67)×10^-5~(2.70±0.29)×10^-1],而tet(Q)、tet(W)在厌氧污泥中的相对丰度为(1.66±0.03)×10^-2~(7.48±1.22)×10^-2,比好氧污泥中(1.94±0.12)×10^-3~(2.85±0.16)×10^-2]高1个数量级;转移因子intI1和ISCR3在厌氧污泥中相对丰度范围为(1.48±0.01)×10^-3~(2.61±0.31)×10^-2,显著低于好氧污泥(1.18±0.15)×10^-1~(8.99±0.75)×10^-1],表明厌氧处理过程中由这两种转移因子介导的水平转移潜力较小.研究表明,好氧处理促进了tet(A)、tet(G)、tet(X)的传播,但对tet(Q)和tet(W)有控制效果,而厌氧处理过程与之相反.抗药基因的分布与水平转移因子、抗药机制、群落结构有关.

Characteristics of tetracycline resistance genes in the anaerobic and aerobic treatment of tetracycline production wastewater

In order to understand the characteristics of antibiotic resistance genes (ARGs) in the anaerobic and aerobic treatment processes of two tetracycline production wastewater, the abundances and distribution of six frequently reported tetracycline resistance genes (tet(A), tet(C), tet(G), tet(Q), tet(W), and tet(X)) and two types of mobile elements (intI1 and ISCR3) were determined by PCR and quantitative PCR (qPCR). tet(C) was detected in none of the samples, while the others were discovered in all of the samples. In the systems of the tetracycline production wastewater, the relative abundances (normalized to 16S rRNA genes) of tet(A), tet(G), tet(X) in the anaerobic sludge((1.25±0.16)×10^-4~(4.52±0.002)×10^-2) were lower than those in the aerobic sludge ((9.88±0.67)×10^-5~(2.70±0.29)×10^-1), while the relative abundances of tet(Q) and tet(W) in the anaerobic sludge ((1.66±0.03)×10^-2~(7.48±1.22)×10^-2) were significantly higher than those in the aerobic sludge (1.94±0.12)×10^-3~(2.85±0.16)×10^-2). Besides, the relative abundances of intI1 and ISCR3 in the anaerobic sludge ((1.48±0.01)×10^-3~(2.61±0.31)×10^-2) were significantly lower than those in the aerobic sludge ((1.18±0.15)×10^-1~(8.99±0.75)×10^-1), showing that the potential of horizontal gene transfer mediated by the mobile elements is lower in the anaerobic treatment process. It is indicated that aerobic treatment may facilitate the spread of tet(A), tet(G) and tet(X) but control the spread of tet(Q) and tet(W) in tetracycline production wastewater, with the opposite situation in the anaerobic treatment. The different distribution of tet genes was related to mobile genetic elements, resistance mechanism, and community structure.