Table_1_Changes in the Drinking Water Microbiome: Effects of Water Treatments Along the Flow of Two Drinking Water Treatment Plants in a Urbanized Area, Milan (Italy).xlsx

While safe and of high quality, drinking water can host an astounding biodiversity of microorganisms, dismantling the belief of its “biological simplicity.” During the very few years, we are witnessing an exponential growth in scientific publications, exploring the ecology hidden in drinking water treatment plants (DWTPs) and drinking water distribution system (DWDS). We focused on what happens to the microbial communities from source water (groundwater) throughout the main steps of the potabilization process of a DWTP, located in an urbanized area in Northern Italy. Samples were processed by a stringent water filtration to retain even the smallest environmental bacteria and then analyzed with High-Throughput DNA Sequencing (HTS) techniques. We showed that carbon filters harbored a microbial community seeding and shaping water microbiota downstream, introducing a significant variation on incoming (groundwater) microbial community. Chlorination did not instantly affect the altered microbiota. We were also able to correctly predict (through machine learning analysis) samples belonging to groundwater (overall accuracy was 0.71), but the assignation was not reliable with carbon filter samples, which were incorrectly predicted as chlorination samples. The presence and abundance of specific microorganisms allowed us to hypothesize their role as indicators. In particular, Candidatus Adlerbacteria (Parcubacteria), together with microorganisms belonging to Alphaproteobacteria and Gammaproteobacteria, characterized treated water, but not raw water. An exception, confirming our hypothesis, is given by the samples downstream the filters renewal, which had a composition resembling groundwater. Volatility analysis illustrated how carbon filters represented an ecosystem that is stable over time, probably bearing the environmental conditions that promote the survival and growth of this peculiar microbial community.

尽管饮用水安全且品质优良，但其宿主的微生物多样性却极为惊人，颠覆了人们对其“生物简易性”的固有认知。近数年来，探索饮用水处理厂（Drinking Water Treatment Plants, DWTPs）与饮用水输配系统（Drinking Water Distribution System, DWDS）内隐藏生态的科研文献呈指数级增长，这一态势正为学界所瞩目。本研究聚焦意大利北部某城市化区域内一座饮用水处理厂的净水全流程，追踪原水（地下水）中的微生物群落随各主要处理环节的变化情况。研究通过严苛的水体过滤流程捕获哪怕是体积最小的环境细菌，随后采用高通量DNA测序（High-Throughput DNA Sequencing, HTS）技术对样本进行分析。结果显示，活性炭滤池定植的微生物群落会作为种源，对下游水体微生物组进行塑造，显著改变原水（地下水）的微生物群落组成。氯化消毒并未立即对已发生改变的微生物群落产生影响。通过机器学习分析，我们能够准确区分出原水（地下水）样本（整体准确率达0.71），但却无法可靠识别活性炭滤池样本——此类样本被错误预测为氯化消毒后的样本。特定微生物的存在与丰度特征，使我们得以推测其作为指示菌的潜在作用。具体而言，候选Adlerbacteria属（Candidatus Adlerbacteria，Parcubacteria）与隶属于α-变形菌纲（Alphaproteobacteria）、γ-变形菌纲（Gammaproteobacteria）的微生物共同构成了处理后水体的特征群落，而原水并不具备此类特征。滤池更新后的下游样本是验证该假说的例外：其群落组成与地下水高度相似。波动性分析结果表明，活性炭滤池是一个长期稳定的生态系统，其内部环境条件或可促进这类特殊微生物群落的存活与增殖。