Department of Environment and Health, Tianjin Institute of Environmental & Operational Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, Tianjin, 300050, China.
Department of Environment and Health, Tianjin Institute of Environmental & Operational Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, Tianjin, 300050, China.
Environ Pollut. 2022 Aug 15;307:119541. doi: 10.1016/j.envpol.2022.119541. Epub 2022 May 24.
Antibiotic resistance genes (ARGs), especially last-resort ARGs (LARGs), are receiving extensive attention as emerging environmental contaminants in groundwater. However, their prevalent intracellular and extracellular patterns and bacterial sources in groundwater remain unclear. Herein, groundwater samples were collected in Tianjin, and characterized based on the profiles of intracellular ARGs (iARGs) and extracellular ARGs (eARGs), as well as the resident bacterial communities and extracellular DNA (eDNA)-releasing bacterial communities. The quantitative real-time PCR assays showed that eARGs presented fewer subtypes than iARGs and generally displayed lower detection frequencies than the corresponding iARGs. Similarly, LARGs exhibited lower detection frequencies than common ARGs, but the total abundance showed no significant differences between them. Genes vanA and bla were the observed dominant LARGs, and aadA was the observed common ARG independent of location inside or outside the bacteria. Furthermore, the top 10 phyla showed much difference between the main eDNA-releasing bacteria and the dominant resident bacteria. Proteobacteria was the predominant resident bacterial phyla while dominating the source of eDNA in groundwater. Despite representing a minor portion of the abundance in the resident bacteria, Actinobacteriota, Acidobacteriota, and Chloroflex surprisingly accounted for a large majority of eDNA release. Co-occurrence patterns among persistent ARGs, the resident bacteria, and eDNA-releasing bacteria revealed that the dominant common iARG aadA and intracellular LARGs bla and vanA had significant positive correlations with Methylobacterium_Methylorubrum and Shewanella. Meanwhile, the dominant extracellular LARG bla may be released by bacteria belonging to at least five genera, including Ellin6067, Bifidobacterium, Blautia, Veillonella, and Dechloromonas. Collectively, the findings of this study extend our understanding regarding the distribution of ARGs and their bacterial sources in groundwater, and indicate the serious pollution of LARGs in groundwater, which poses potential risks to public health.
抗生素耐药基因（ARGs），尤其是最后手段抗生素耐药基因（LARGs），作为新兴的环境污染物，在地下水环境中受到广泛关注。然而，它们在地下水中普遍存在的细胞内和细胞外模式以及细菌来源尚不清楚。本研究采集了天津地区的地下水样本，基于细胞内抗生素耐药基因（iARGs）和细胞外抗生素耐药基因（eARGs）的特征，以及驻留细菌群落和释放细胞外 DNA（eDNA）的细菌群落进行了表征。定量实时 PCR 检测结果表明，eARGs 的亚型少于 iARGs，且其检测频率通常低于相应的 iARGs。同样，LARGs 的检测频率低于常见的 ARGs，但它们的总丰度没有显著差异。基因 vanA 和 bla 是观察到的主要 LARGs，而 aadA 是观察到的独立于细菌内外位置的常见 ARG。此外，主要的 eDNA 释放细菌和优势驻留细菌之间的前 10 个门表现出很大的差异。变形菌门是主要的驻留细菌门，也是地下水中 eDNA 的主要来源。尽管在驻留细菌的丰度中所占比例较小，但放线菌门、酸杆菌门和绿屈挠菌门出人意料地占据了 eDNA 释放的大部分。持久抗生素耐药基因、驻留细菌和释放 eDNA 的细菌之间的共现模式表明，主要的常见细胞内 ARG aadA 和细胞内 LARGs bla 和 vanA 与 Methylobacterium_Methylorubrum 和 Shewanella 呈显著正相关。同时，主要的细胞外 LARG bla 可能由至少五个属的细菌释放，包括 Ellin6067、双歧杆菌、Blautia、韦荣球菌和脱氯单胞菌。总的来说，本研究的结果扩展了我们对地下水环境中 ARGs 及其细菌来源分布的理解，并表明地下水 LARGs 的严重污染对公众健康构成了潜在风险。
