摘要

       抗生素抗性基因 (ARGs) 包括细胞外 ARGs (eARGs) 和细胞内 ARGs (iARGs)，被认为是新出现的环境污染物。尽管在其“热点”污水处理厂 (WWTP) 中对 ARG 进行了广泛的研究，但 eARG 对抗生素耐药性传播的贡献仍不清楚。在这里，我们应用宏基因组测序来研究来自五个污水处理厂的活性污泥中 eARGs 的分布、流动性和微生物宿主。总相对丰度eARGs范围从9.5×10-6到1.3×10-4，主要包括elfamycin、双药和氨基糖苷类抗性基因。多个 eARG（例如，EF-Tu、ropB 和 rpsL 突变体）在五个污水处理厂之间共享，并且一些聚集在相同的遗传元件中（例如，EF-Tu-rpsJ）。发现 eARG 经常与 eMGE（例如 sul1-3'CS-TnAs3、sul2-intI1-ISVsa3 和 tetX-p63039）共定位，这可能有助于 eARG 的动员。大多数 eARG 可能起源于分枝杆菌属 (6.7%)、亚硝化单胞菌属 (5.3%)、类固醇杆菌属 (5.3%)、硝化螺菌属 (5.2%) 和假单胞菌属 (5.1%)。在 eARGs 和 iARGs 之间没有观察到多样性、丰度和流动性的显着差异。市政污水处理厂的 eARGs 和 iARGs 的宿主组成始终以亚硝化单胞菌、类固醇杆菌、硝化螺菌和假单胞菌为主，而与来自猪污水处理厂的 eARGs 相比，iARGs 宿主中的一些差异丰富的属（尤其是硝化螺菌属）被鉴定出来。我们的研究结果证实了污水处理厂中的移动 eARGs 库，从而为减轻广泛的抗生素耐药性奠定了基础。

       Antibiotic resistance genes (ARGs) including extracellular ARGs (eARGs) and intracellular ARGs (iARGs), are recognized as emerging environmental contaminants. Despite extensive efforts to profile ARGs in their “hotspots” wastewater treatment plants (WWTPs), the contribution of eARGs to antibiotic resistance spread remains unclear. Here, we applied metagenomic sequencing to investigate the distribution, mobility and microbial hosts of eARGs in activated sludge from five WWTPs. The total relative abundance eARGs ranged from 9.5 × 10−6 to 1.3 × 10−4, mainly encompassing elfamycin, dual drug, and aminoglycoside resistance genes. Multiple eARGs (e.g., EF-Tu, ropB, and rpsL mutants) were shared among the five WWTPs, and some clustered in the same genetic element (e.g., EF-Tu-rpsJ). eARGs were found to frequently co-localize with the eMGEs (e.g., sul1-3′CS-TnAs3, sul2-intI1-ISVsa3, and tetX-p63039), which may facilitate the mobilization of eARGs. Most eARGs likely originated from the genera Mycobacterium (6.7%), Nitrosomonas (5.3%), Steroidobacter (5.3%), Nitrospira (5.2%) and Pseudomonas (5.1%). No significant difference in the diversity, abundance, and mobility was observed between eARGs and iARGs. The host composition of eARGs and iARGs from municipal WWTPs are consistently dominated by Nitrosomonas, Steroidobacter, Nitrospira and Pseudomonas, while some differentially enriched genera (especially Nitrospira) in the hosts of iARGs compared with those of eARGs from the swine WWTP were identified. Our findings corroborate the mobile eARGs reservoir in WWTPs, thereby laying foundation for mitigating widespread antibiotic resistance.

https://www.sciencedirect.com/science/article/abs/pii/S0043135419305615