College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China; Environmental Futures Research Institute, School of Environment and Science, Griffith University, Brisbane 4111, Australia.
Sci Total Environ. 2021 Mar 20;761:143205. doi: 10.1016/j.scitotenv.2020.143205. Epub 2020 Oct 28.
Grazing is expected to exert a substantial influence on antibiotic resistance genes (ARGs) in grassland ecosystems. However, the precise effects of grazing on the composition of ARGs in grassland soils remain unclear. This is especially the case for grassland soils subject to long-term grazing. Here, we investigated ARGs and bacterial community composition in soils subject to long-term historic grazing (13-39 years) and corresponding ungrazed samples. Using a combination of shotgun metagenomics, amplicon analyses and associated soil physicochemical data, we provide novel insights regarding the structure of ARGs in grassland soils. Interestingly, our analysis revealed that long-term historic grazing had no impacts on the composition of ARGs in grassland soils. An average of 378 ARGs, conferring resistance to 14 major categories of antibiotics (80%), were identified in both grazing and ungrazed sites. Actinobacteria, Proteobacteria and Acidobacteria were the most prevalent predicted hosts in these soils and were also shown to harbour genetic capacity for multiple-resistant ARGs. Our results suggested that positive effects of bacterial community composition on ARGs could potentially be controlled by affecting MGEs. Soil properties had direct effects on the composition of ARGs through affecting the frequency of horizontal gene transfer among bacteria. Twelve novel ARGs were found in S. grandis steppe grasslands, indicating that different vegetation types might induce shifts in soil ARGs. Collectively, these findings suggest that soil properties, plants and microorganisms play critical roles in shaping ARG patterns in grasslands. Together, these data establish a solid baseline for understanding environmental antibiotic resistance in grasslands.
放牧预计会对草原生态系统中的抗生素抗性基因（ARGs）产生重大影响。然而，放牧对草原土壤中 ARG 组成的确切影响尚不清楚。特别是对于长期受到放牧影响的草原土壤更是如此。在这里，我们研究了长期历史放牧（13-39 年）和相应未放牧的草原土壤中的 ARGs 和细菌群落组成。我们使用组合式鸟枪法宏基因组学、扩增子分析和相关土壤理化数据，为草原土壤中 ARG 的结构提供了新的见解。有趣的是，我们的分析表明，长期历史放牧对草原土壤中 ARG 的组成没有影响。在放牧和未放牧的地点都平均鉴定出 378 个 ARG，这些 ARG 对 14 类主要抗生素（80%）具有抗性。放线菌、变形菌和酸杆菌是这些土壤中最常见的预测宿主，并且还显示出对多种耐药性 ARG 的遗传能力。我们的结果表明，细菌群落组成对 ARGs 的积极影响可能通过影响 MGE 来控制。土壤特性通过影响细菌之间水平基因转移的频率，直接影响 ARGs 的组成。在沙冬青草原中发现了 12 个新的 ARG，这表明不同的植被类型可能会引起土壤 ARG 的变化。总的来说，这些发现表明土壤特性、植物和微生物在塑造草原 ARG 模式方面发挥着关键作用。这些数据共同为理解草原环境中的抗生素抗性奠定了坚实的基础。
