京津冀典型地区再生水灌溉农田土壤抗生素抗性基因分布特征与演变模式

Widespread applications of antibiotics result in enrichment of antibiotic residues in wastewater which, as a consequence, accelerates the development of microbial antibiotic resistance. Release of these substances to the environment via reclaimed water irrigation or discharge causes high risks to environmental and public health due to potential emergence of antimicrobial resistance and spreading/propagation of antibiotic resistance-encoding genes (ARGs), typically in semi-arid region in Northern China. A key to the environmental dynamics of antibiotics and ARGs in soil is the spatiotemporally heterogeneous soil physical characteristics and the flickering aqueous network that foster chemical transportation, bacterial activity, and a variety of biophysical and genetic interactions. The interplay of these variables may define spheres of influence that shape antibiotic resistant bacteria (ARB) with respect to space, time, and numerous biophysical and genetic interactions that lead to potential mechanisms for the spatiotemporal dynamics and fate of antibiotic resistance populations in arable lands receiving wastewater irrigation, yet the underlying mechanisms remain unclear. Coupling experimental investigations and mathematical modelling, the goal of the project is attempt to increase our knowledge of the extent and abundance of typical (tetracyclines and β-lactams antibiotics) ARGs and ARB and their transmission mechanisms in reclaimed water irrigated arable lands, by linking soil porous structure properties, physics of small-scale water organization, and resulting diffusion patterns of nutrients and other chemical compounds with bacterial motility, growth, resistance genes transferring and numerous interactions. The targeted research area, Beijing–Tianjin–Hebei region, is among the five majority wastewater irrigation regions facing severe antibiotics pollution. The project foresees three interlinked subprojects that will provide the necessary foundation and synergy towards exploring the extent and origin of microbial antibiotic resistance and their dissemination dynamics and patterns, as well as the abundance and diversity of ARB and their transportation dynamics in arable lands receiving reclaimed water, which are essential for risks assessment and practical control protocols.

抗生素的大量使用导致抗性基因和抗生素残留在污水中富集、促进抗性基因向致病性细菌转移，引发严峻的公共健康和生态安全风险。再生水灌溉或污水处理厂二次出水的直接排放是其进入土体等环境的重要渠道，尤其在我国北方水资源缺乏地区。我国是世界上最大的抗生素使用国，由此引发的抗性基因污染形势严峻。然而，抗性基因在环境中的传播和扩散机制尚未明确，成为制约抗性基因污染引发的公共健康和生态安全风险的有效评估、以及潜在的安全防护和生态修复等理论和实践研究的瓶颈。本课题以京津冀典型地区接受再生水灌溉农田土壤为研究对象，综合利用高通量测序和多变量相关性分析等研究手段，探究再生水灌溉农田土壤中四环素类和β-内酰胺类等典型抗生素抗性基因的时空分布特征；并通过微观试验和土壤微生物过程计算机模型，从不同尺度解析抗性基因在土壤中的传播扩散过程机制，揭示抗生素抗性基因在京津冀典型地区再生水灌溉农田土壤中传播和扩散及演变模式。

土壤环境中抗生素抗性基因的传播和扩散容易引发严峻的公共健康和生态安全风险。本研究聚焦农田土壤微生物抗性基因的传播扩散规律与调控机制等关键科学问题，成功开发并创建了基于全息显微成像和荧光共聚焦显微成像等技术的土壤抗生素抗性细菌生物地球化学界面过程原位观测试验平台和计算机仿真模型模拟试验平台，并应用此模拟和试验系统研究揭示了土壤微观孔隙、水分和养分特征等关键环境因子及其动态变化对土壤微生物群落组成、细菌抗性基因水平迁移以及细菌群落结构演变的影响和调控机制。研究发现土壤环境中普遍存在的微观液滴蒸发产生的咖啡环效应能够显著增加细菌抗性基因的水平转移，而复杂微生物群落中细菌能够通过分泌胞外聚合物调节生物膜结构、进而影响种群之间的水平基因传递，同时，复杂土壤微生物群落中普遍存在的真菌菌丝结构能够为个体细菌及包含抗性基因的细菌质粒等提供适宜的运动与扩散传输通道，显著促进微生物种群的空间拓殖能力与水平基因转移效率以及提升微生物群落的空间自组织程度，进而优化了复杂微生物群落的多样性维持机制和种群演化模式；相关研究结果有助于进一步了解抗生素抗性基因在环境中的传播扩散，对预测其污染的危害程度、引起人们对抗生素抗性基因污染的重视有重要意义，同时对限制环境中抗生素抗性基因的水平转移，控制、降低其污染程度具有指导作用。以上研究成果共计发表了高水平研究论文 21 篇（其中包含中科院一区论文 4 篇和二区论文 3 篇），第一标注 13 篇、第二标注 5 篇、第三标注 2 篇、第四标注 1 篇；培养了研究生 5 名，其中，博士生 3 名、硕士生2名。