城市供水系统对水中真菌数量和群落结构的影响

Effect of urban water supply system on fungi population and community structure

摘要:

【背景】对于饮用水中的微生物污染，绝大多数研究集中在细菌、病毒及原虫和蠕虫。由于真菌中包含多种潜在致病菌，应当引起人们的关注。【目的】研究城市供水系统中真菌数量、群落组成变化及可能存在的潜在致病真菌。【方法】利用MEA和RB两种培养基，对供水系统中的原水和两个水厂净水工艺过程及不同供水模式用户龙头水样进行培养法计数统计。提取上述样本总DNA，并应用Illumina MiSeq平台进行ITS1区高通量测序。【结果】从15个样本中共获得有效序列579 470条，1 260个OTU，包含8个门26个纲67个目228个属的真菌。门水平上子囊菌门真菌为供水系统优势真菌，属水平上不同样本存在差异，但曲霉属和枝顶孢属真菌在所有样本中均存在；培养法和高通量测序结果共同显示，活性炭过滤出水真菌数量和物种丰富度均较前一工艺有所上升；氯化消毒对真菌数量、物种多样性及物种组成影响显著；经过供水管网输配和二次供水设施后，用户龙头水样本真菌数量和物种丰富度明显高于出厂水。【结论】供水系统中的优势真菌为子囊菌门(Ascomycota)，该门真菌可穿透净水工艺过程的多级屏障；水厂净水工艺能有效去除水中可培养真菌，生物活性炭过滤工艺能够影响真菌数目及物种多样性；供水管网及二次供水设施是末端饮用水中真菌污染的重要来源；供水系统中存在潜在致病真菌。

Abstract:

[Background] The majority of studies on microbial contamination in drinking water focuses on bacteria, viruses, protozoa and worms, but less on fungi. We should also pay attention to fungi that contains a variety of potential pathogenic groups. [Objective] To study the changes in population and community structure of fungi and potential pathogenic fungi that may exist in urban water supply systems. [Methods] Two culture media (MEA and RB) were used to study the raw water, the purified water from two waterworks and the tap water from different secondary water supply modes in water supply systems. The total DNA of the above samples was extracted and the Illumina Miseq platform was used for high-throughput sequencing of the ITS1 gene. [Results] According to the high-throughput sequencing data, 579 470 effective sequences and 1 260 OTUs were obtained from 15 samples. The 228 fungal genera belong to 67 orders, 26 classes, and 8?phylum. The dominance of Ascomycota in water supply systems and fungal genera such as Aspergillus and Acremonium were present in all samples but rest were varied from samples to samples. The results of culture dependent and high-throughput sequencing showed that the population and species richness of fungi rose after filtering by biological activated carbon. Chlorination had a significant effect on the quantity, diversity and community of fungi. After passing through the water distribution systems and secondary water supply facilities, tap water sample showed significantly higher data in the quantity and species richness of fungi than effluent water. [Conclusion] The dominant fungi in the water supply system belong to Ascomycota and the dormant fungal spore can penetrate the multi-stage barriers in the water treatment process. The water purification process can effectively remove culturable fungi from water, and the biological activated carbon filtration process can lead a fungus leakage. Water supply pipelines and secondary water supply facilities are important sources of fungal contamination in drinking water and potentially pathogenic fungi that can cause infections exist in water supply systems.