In drinking water distribution systems, previous research on viruses has focused on tracking and eliminating viral pathogens to limit the spread of waterborne diseases. However, viruses may impact drinking water quality and human health in other less direct ways by influencing the proliferation of bacteria that can both lead to human disease, as well as exacerbate water quality issues from nitrification and corrosion. Previous metagenomics studies have focused on how bacteria influence water quality, at most identifying the presence of viral proteins or estimating the viral fraction. For this reason, fundamental information about how viruses influence microbial populations in drinking water remains unknown. In this presentation, I will address this gap by providing an overview of global drinking water viral assemblages using sequences mined from publicly available drinking water metagenomes. These sequences provide a first glimpse of the taxonomic and metabolic diversity of the drinking water virome, as well as indicate the parameters shaping viral diversity. Environmental conditions, as well as differences in sample collection and processing were found to influence the viral assemblages. Differences in water quality between distribution systems that used residual disinfectants and those that did not led to clear differences in the viral taxonomic diversity and metabolic potential of these samples. For instance, drinking water distribution systems that used a residual disinfectant had fewer distinct viral populations (observed taxa; Wilcoxon rank sum test p-value = 0.0003) and less even viral assemblages (Shannon index; Wilcoxon rank sum test p-value = 0.0001). Additionally, genes related to surviving oxidative stress were overabundant in distribution systems that used a residual disinfectant, while genes related to nitrogen metabolism were overabundant in distribution systems without a residual disinfectant. Laying important groundwork for better understanding the impact that viruses have on the bacteria of drinking water distribution systems, this study demonstrates that viral assembleges are diverse across drinking water systems and shaped by treatment choices, including the use of a residual disinfectant.
