摘要

有必要进一步了解对氯消毒对抗生素抗性基因（ARG）的影响，以推进相关的饮用水，废水和再利用处理。然而，很少有研究明确评估对DNA的物理影响。在这里，我们检查了游离氯（1-20 mg Cl2 / L）对细胞外基因组，质粒DNA和选择ARGs的影响。相对于无氯对照，发现氯化将细胞外基因组和质粒DNA的荧光信号（范围从0.005至0.05μg/ mL）降低70％。使用生物分析仪进一步对得到的DNA进行片段分析，表明氯化导致片段化。此外，氯还有效地分别使染色体和质粒携带的ARG，mecA和tetA失活。对于浓度> 2 mg Cl2 // L×30 min，当ARG的初始浓度为105拷贝/μL或更低时，氯有效地降低了qPCR信号。值得注意的是，基因组DNA和mecA基因信号比质粒携带的tetA基因更容易被氯减少（约2倍）。基于qPCR短（~200 bps）和长扩增子（~1200 bps）的结果，氯化可破坏ARG的完整性，这可能降低自然转化的可能性。总的来说，我们的研究结果有力地说明氯化可能是灭活细胞外染色体和质粒携带的DNA和ARG的有效方法。

There is a need to improve understanding of the effect of chlorine disinfection on antibiotic resistance genes (ARGs) in order to advance relevant drinking water, wastewater, and reuse treatments. However, few studies have explicitly assessed the physical effects on the DNA. Here we examined the effects of free chlorine (1–20 mg Cl2/L) on extracellular genomic, plasmid DNA and select ARGs. Chlorination was found to decrease the fluorometric signal of extracellular genomic and plasmid DNA (ranging from 0.005 to 0.05 μg/mL) by 70%, relative to a no-chlorine control. Resulting DNA was further subject to a fragment analysis using a Bioanalyzer, indicating that chlorination resulted in fragmentation. Moreover, chlorine also effectively deactivated both chromosomal- and plasmid-borne ARGs, mecA and tetA, respectively. For concentrations >2 mg Cl2//L × 30 min, chlorine efficiently reduced the qPCR signal when the initial concentration of ARGs was 105 copies/μL or less. Notably, genomic DNA and mecA gene signals were more readily reduced by chlorine than the plasmid-borne tetA gene (by ~2 fold). Based on the results of qPCR with short (~200 bps) and long amplicons (~1200 bps), chlorination could destroy the integrity of ARGs, which likely reduces the possibility of natural transformation. Overall, our findings strongly illustrate that chlorination could be an effective method for inactivating extracellular chromosomal- and plasmid-borne DNA and ARGs.

https://link.springer.com/article/10.1007/s11783-019-1124-5