河床微生物驱动的抗生素降解过程及机理

The treated wastewater (reclaimed water) has been widely used as eco-environmental water to restore flow in dried river beds, especially in the water scarce areas. However, it can cause serious water pollution problems, as reclaimed water contains various trace organic contaminants which are persistent and toxic. One of these infamous contaminants is antibiotic. Antibiotics comprise an important pharmaceutical group, yet they have been used extensively. Despite of the relatively low concentrations in the environment (ng/L ~ μg/L), antibiotics can perturb microbial ecology, increase the antibiotic resistance in microorganisms, and in turn is a growing public health concern. To protect ecosystem and human health, an improved understanding of removal processes regulating antibiotics degradation in natural waters is needed. .As one of the most promising clean-up technologies, biological removal process has low costs and the potential to completely remove contaminants. Therefore, this project is to study the efficacy and mechanism of antibiotics bio-degradation by riverbed sediments via lab-scale experiments. Both long-term column tests and batch tests will be conducted. Riverbed sediments will be incubated in columns or flasks to simulate and evaluate riverbed infiltration, while the difference is that 14C-labelled antibiotics will be added in batches. Redox conditions and influent substrates will be manipulated. The analysis of removal performance under different operation conditions will help to reveal the underlying degradation mechanisms – co-metabolism or mineralization, and to assess its degradation/mineralization kinetics. Moreover, the evolution of microbial communities and antibiotic resistant genes will be analyzed during degradation operation. Results will clarify the potential relations between microbial diversity with microbial functionality to degrade antibiotics or to transfer relevant resistance genes. Overall, the comprehensive understanding of the involved microbial groups and the bio-degradation mechanisms will favor the strategies for enhancing bioremediation of antibiotics, meanwhile promoting the tools for proper management in other biologically-mediated pollution treatment processes.

利用再生水作为环境用水补充日益干枯的河道，已成为资源性缺水地区用于维持地表水生态系统平衡的有力措施之一。然而，再生水体含有多种难降解且具有生物毒性的微量有机化合物，由此引发的环境风险问题如下渗污染含水层不可忽视。抗生素类药物应用广泛，而其微量残留即可增加自然环境中细菌的耐药性，导致抗生素抗性基因的出现，被世界卫生组织认为是威胁人体健康的重大问题。因此，本项目拟开展收纳再生水河道河床底泥中残留抗生素生物降解过程及机理的研究。利用室内连续流柱实验模拟河床渗滤过程，结合碳-14标记的抗生素同位素批次实验，验证不同实验条件下（氧化还原条件、生长基质）关于矿化和共代谢机理的不同科学假说，获得动力学参数；同时表征降解过程中微生物菌群演化和抗性基因丰度变化，探究不同底泥菌群结构对其生物降解能力或抗性基因转移扩散的影响，为基于自然的环境风险管控技术提供理论依据，对微生物调节的其他绿色修复手段具有参考价值。

利用再生水补给环境用水已成为水资源调控和配置的有力措施之一；然而，再生水体中抗生素类药物残留引发的细菌耐药性增加和抗性基因传播等生态风险不容忽视。..本项目研究了再生水收纳河道中磺胺类抗生素的生物降解机理及迁移转化过程。首先，利用批次实验评估了不同磺胺类的自然衰减现象，发现在28天室内去除实验中三种抗生素变化趋势一致，生物降解为主要去除途径（44.4±32.0%），吸附去除率为5.4±3.5%而矿化去除率小于1%，表明其生物降解不彻底同时可生成多种仍具有潜在代谢活性的中间代谢产物。实验中磺胺类浓度时间变化显示其降解动力学受氧化还原条件影响，好氧条件和反硝化条件下半衰期分别为24.9±27.6天、87.2±71.2天；中间代谢产物浓度时间变化证实了脱氨基作用为其主要转化反应，并且反硝化条件下磺胺类降解过程可逆，导致其半衰期较长且变化范围较大。此外，随着磺胺类的降解去除，沉积物中sul抗性基因丰度降低，然而微生物群落组成无显著性变化；相比于菌群结构，沉积物有机质含量对抗生素降解影响更显著。..基于对磺胺类降解机理的认识，在室内开展了连续流柱实验模拟河床渗滤去除抗生素过程，发现去除仍以生物降解为主，然而在溶质停留时间有限条件下（0.6-2.8天）不同磺胺类去除效率不同；结合出水水质分析，推测磺胺甲噁唑在铁还原环境下发生其特有的降解反应。进水中ppm有机碳或无机氮添加亦可改变磺胺类的降解效率，结合不同柱深度水质监测数据，发现进水有机碳通过调节柱内氧化还原区分布从而影响降解反应，而进水无机氮则同时富集了可对微量有机物发生共代谢去除的硝化细菌。..再生水广泛回用的情景下难降解性微量有机物的污染风险普遍存在，该项目的研究结果可为基于自然调节的污染风险管控提供理论依据，对微生物驱动的绿色修复技术具有一定的参考价值。