城市二次供水系统中条件致病菌再生长机制和微生物生态学研究

Opportunistic pathogens (OPs) are emerging waterborne pathogens that naturally establish and grow in drinking water, posing a unique challenge to drinking water safety in secondary water supply. The aims of this project are: 1) to investigate the occurrence and regrowth potential of OPs (i.e., Legionella pneumophila, nontuberculosis mycobacteria, Pseudomonas aeruginosa) and amoeba hosts in several representative real-world secondary water supply systems; 2) to explore mixed effects of water chemistry, water tank liner and pipe materials, hydraulic retention time and flow rate on regrowth potential of OPs and microbial community structures and compositions under lab-controlled conditions; 3) to clarify the microbial ecological mechanisms (e.g., interactions between amoeba-resistant bacteria (ARB), amoeba, and indigenous bacteria) governing the regrowth of OPs by employing high through-put sequencing of phylogenetic marker genes (i.e., 16S and 18S rRNA genes) and metagenomes. The outcomes of this project include improved understanding of OPs regrowth mechanisms in secondary drinking water supply, as well as establishment of qualitative and/or quantitative relationships between engineering factors, water chemistry and drinking water microbiological safety. The results of this project will provide insights and supporting data to health risk assessment of OPs in secondary water supply, and assist in formulating practical guidance for secondary water supply system design and management, as well as selection and optimization of OPs mitigation strategies.

条件致病菌（Opportunistic pathogens, OPs）是新发饮用水病原微生物，能在饮用水体系中再生长，对城市二次供水系统的饮用水微生物学安全性构成潜在威胁。本项目将研究三种OPs（噬肺军团菌、非结核性分枝杆菌、铜绿假单胞菌）及其阿米巴原虫宿主在实际二次供水系统中分布及再生长规律，分析其产生机制；采用实验室模拟二次供水系统，研究饮用水化学性质、水箱和管网材质、停留时间、流速等多个因素对OPs再生长潜力的影响，探索二次供水系统属性、饮用水化学性质和微生物学安全性之间的联系；将通过对16S和18S rRNA基因及宏基因组进行高通量测序，深度剖析OPs和不同种属阿米巴原虫、固有细菌相互作用的微生物生态学机理，探寻OPs微生态学控制手段。本项目所得结论可为评价二次供水系统饮用水微生物学安全性，指导二次供水设施设计和改造，降低OPs介水传播疾病风险提供理论支持和科学依据。

二次供水系统由水箱、水泵、建筑物内部管网等基础设施构成，用于补偿市政管网供水压力不足。二次供水系统因较长的水力停留时间、材料腐蚀、存在沉淀物等原因易受微生物污染。条件致病菌是一类新发饮用水病原微生物，能在饮用水系统中再生长，对城市二次供水系统微生物学安全构成潜在威胁。项目以多种条件致病菌（如，嗜肺军团菌,非结核性分枝杆菌）及其阿米巴原虫宿主为研究对象，通过对不同类型二次供水系统（单水箱供水、单水池供水、水箱-水池联用）的多位点监测，证实了二次供水系统中的水箱、水池是条件致病菌再生长的关键部位，不同类型二次供水系统对条件致病菌和微生物群落结构变化的影响程度也不尽相同；通过对特殊环境（医院）二次供水系统的调查，揭示了医院供水系统较高的鸟分枝杆菌污染水平（和普通供水系统比较），以及建筑物使用功能及管网属性对用户端龙头水微生物的不同影响；通过模拟实验，揭示了水箱材质、停留时间等因素对不同条件致病菌的差异化影响。项目还利用高通量测序、生信学分析、统计学分析相结合的手段，剖析了饮用水微生物群落结构中条件致病细菌、阿米巴原虫、固有细菌相互作用的微生物生态学机制。本研究建立了二次供水系统属性、饮用水化学性质和微生物学安全性之间的联系，所得结论可为评价二次供水系统微生物安全性，指导二次供水设施设计、改造和管理，降低条件致病菌介水传播疾病风险提供数据参考。