Microbial survival in drinking water systems.

Drinking water process operations focus on physical removal, chemical/UV light inactivation, or starvation through nutrient removal as the primary means of microbial control. Yet, every liter of regulation compliant drinking water contains millions of phylogenetically diverse microbial cells. This microbial community is not always a reflection of inadequate treatment or water supply contamination. Rather, it is likely a result of the ability of specific microorganisms to persist inspite/because of selective pressures imposed on them by engineering interventions. Through an extended spatial-temporal survey using 16S rRNA gene amplicon sequencing data at a representative drinking water system, we demonstrate that treatment processes impose strong selective pressures on microbial communities introduced into it from the source waters. In particular, source water microorganisms that are able to colonize filtration processes are successfully able to survive in the drinking water distribution systems under chronic disinfectant stress. To understand the metabolic basis for this observation, we utilized metagenomic sequencing to assemble and extract >50 near complete draft genomes of bacteria that dominate the microbial community in these drinking water filters. Through a comparative analyses of the metabolic potential of these draft genomes, we have identified a likely link between nitrogen starvation and disinfection resistance – which could have important process implications for microbial control in drinking water systems.