A Snapshot of the Global Drinking Water Virome: Diversity and Metabolic Potential Vary with Residual Disinfectant Use

Abstract

Viruses are important drivers of microbial community ecology and evolution, influencing microbial mortality, metabolism, and horizontal gene transfer. However, the effects of viruses remain largely unknown in many environments, including in drinking water systems. Drinking water metagenomic studies have offered a whole community perspective of bacterial impacts on water quality, but have not yet considered the influences of viruses. In this study, we address this gap by mining viral DNA sequences from publicly available drinking water metagenomes from distribution systems in six countries around the world. These datasets provide a snapshot of the taxonomic diversity and metabolic potential of the global drinking water virome, and provide an opportunity to investigate the effects of geography, climate, and drinking water treatment practices on viral diversity. Both environmental conditions and differences in sample processing were found to influence the viral composition. Using free chlorine as the residual disinfectant was associated with clear differences in viral taxonomic diversity and metabolic potential, with significantly fewer viral populations and less even viral community structures than observed in distribution systems without residual disinfectant. Additionally, significantly more viral-encoded genes involved in mitigating oxidative stress were observed in systems that use free chlorine, while significantly more viral genes involved in nitrogen metabolism were observed in systems that do not. Through this study, we have demonstrated that viral communities are diverse across drinking water systems and vary with the use of residual disinfectant. Our findings offer directions for future research to develop a more robust understanding of how virus-bacteria interactions in drinking water distribution systems affect water quality.

Identifying eukaryotes in drinking water metagenomes and factors influencing their biogeography

“…The presence of such correlation, observed also by Yeh and Fuhrman 107 , is concordant with the “diversity begets diversity” hypothesis 108 , likely arising due to interactions between populations across superkingdoms 6 which expand the availability of ecological niches and thus enhances diversity. Both Figures 3a and 3b, further underline the effect of disinfection of the DWDS microbiome, highlighting, in accordance with to Dai 31 and Hegarty 109 and colleagues, the effect of disinfection strategies on the beta diversity of prokaryotic and viral communities in DWDSs and suggesting a lower effect for eukaryotes (median Mash differences: eukaryotes = 0.021; prokaryotes = 0.068; viruses = 0.043). While this result is concordant with the higher chlorine resistance of eukaryotes 6,96,97 , it should be noted that given the likely undersampling of eukaryotic communities in DWDSs, such result might be biased towards the most abundant eukaryotes and that further dedicated studies would be needed to confirm it.…”

Disinfectant Stress Enhances Prokaryotic Symbiosis with Lysogenic Phages and Defense Systems Against Detrimental Phage Infection

“…The drinking water distribution system (DWDS) is an important platform to study ecological drivers for adaptation to stress via prokaryote-phage symbiosis, and the corresponding response of prokaryotic antiviral defense systems. Speci cally, DWDS experience nutritional limitation [24] and oxidative stress induced by residual disinfectants [25] as potential drivers for prokaryote-phage symbiosis. Moreover, the DWDS microbiome is a key determinant of drinking water safety and public health, so elucidating such microbial interactions may enhance risk assessment of waterborne pathogens propagation and inspire ecologically-informed microbial control strategies.…”