Maintaining a disinfectant residual is a key approach for controlling microbial growth in drinking water distribution systems and is routine practice in much of the developed world. In contrast, some countries in western Europe provide consumers with drinking water free from disinfectants. Considering the impact of disinfectant residual on the drinking water microbiome and resultant implications for human exposure, it is critical that we assess the its long-term impacts on the drinking water microbial community.  To this end, we have conducted a comparative genomics study of distribution systems in Netherlands, England, Wales, and Scotland. Our goal is to  understand the genome-level impact of disinfection practises on microbial communities in drinking water systems. Specifically, we are interested in understanding (1) whether phylogenetically closely related organisms exhibit key differences in genomic content and metabolic potential between disinfected and non-disinfected systems, and (2) whether these differences may relate to competitive advantages in chemical stressed (i.e. disinfected system) or nutrient stressed (non-disinfected systems) environments.  We have collected 55 samples from the aforementioned four countries for shotgun DNA sequencing along with a range of water quality analyses. The extracted DNA was sequenced on the Illumina HiSeq 2500 to obtain 250-bp paired-end reads and reads were assembled into contigs using iterative de Bruijn graph assembler. The contigs were subject to gene calling followed by annotation against the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Our initial community analyses indicate that while oxidative stress response and dehalogenation genes are more abundant in disinfected systems, overall functional analyses indicate that chloraminated and non-disinfected systems are markedly distinct from chlorinated systems while being highly similar to each other.  This disparity at the functional level is not borne out at the taxonomic level, where community composition of the disinfected and non-disinfected samples were distinct from each other. We are currently analyzing additional this data through an approach involving binning of assembled contigs in metagenome assembled genome to compare functional potential between closely related microbial clusters to understand the role of disinfectant and nutrient stress on selection between closely related microorganisms.

Genome-resolved metagenomics to assess the long-term impact of disinfection on the drinking water microbiome

255th National Meeting (2018)

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