摘要
      Class 1 integrase intI1 has been considered as a good proxy for anthropogenic pollution because of being linked to genes conferring resistance to antibiotics. The gene cassettes of class 1 integrons could carry diverse antibiotic resistance genes (ARGs) and conduct horizontal gene transfer among microorganisms. The present study applied high-throughput sequencing technique combined with anintI1 database and genome assembly to quantify the abundance of intI1 in 64 environmental samples from 8 ecosystems, and to investigate the diverse arrangements of ARG-carrying gene cassettes (ACGCs) carried by class 1 integrons. The abundance of detected intI1 ranged from 3.83 × 10–4 to 4.26 × 10° intI1/cell. High correlation (Pearson’s r = 0.852) between intI1 and ARG abundance indicated that intI1 could be considered as an important indicator of ARGs in environments. Aminoglycoside resistance genes were most frequently observed on gene cassettes, carried by 57% assembled ACGCs, followed by trimethoprim and beta-lactam resistance genes. This study established the pipeline for broad monitoring of intI1 in various environmental samples and scanning the ARGs carried by integrons. These findings supplemented our knowledge on the distribution of class 1 integrons and ARGs carried on mobile genetic elements, benefiting future studies on horizontal gene transfer of ARGs.

      由于与赋予抗生素抗性的基因相关，因此1类整合酶intI1被认为是人为污染的良好替代品。 1类整合子的基因盒可携带多种抗生素抗性基因（ARG）并在微生物之间进行水平基因转移。本研究应用高通量测序技术结合intI1数据库和基因组组装来量化来自8个生态系统的64个环境样品中intI1的丰度，并研究由1类携带的携带ARG的基因盒（ACGC）的多种排列整合。检测到的intI1的丰度范围从3.83×10-4到4.26×10°intI1 /细胞。 intI1与ARG丰度之间的高相关性（Pearson's r = 0.852）表明intI1可以被认为是ARG在环境中的重要指标。氨基糖苷类抗性基因最常见于基因盒，由57％的装配ACGC携带，其次是甲氧苄啶和β-内酰胺抗性基因。本研究建立了对各种环境样品中intI1的广泛监测和扫描整合子携带的ARG的流水线。这些发现补充了我们对1类整合子和ARGs在移动遗传元件上的分布的了解，有助于未来关于ARG水平基因转移的研究。

https://pubs.acs.org/doi/abs/10.1021/acs.est.6b05887