Investigation of Minnesota groundwater bacteria using dead-end ultrafiltration

Groundwater is often a desirable drinking water source because it has low suspended solids and minimal biological activity, often requiring little if any treatment prior to distribution and subsequent consumption. Epidemiological studies have shown, however, that consumption of untreated groundwater increases risk of gastrointestinal illness. In this study, high-volume (300 to 1500 L) dead-end ultrafiltration was used to capture and recover microbes from 16 public groundwater systems throughout Minnesota (United States). Sampling campaigns occurred on three separate dates per water system from 2016 to 2017. During the campaigns, each water system was sampled at the wellhead or source, after treatment (if any), and from one location in the distribution system. DNA was extracted from the microbes recovered in these samples (via backflushing of the ultrafiltration units) and used as template for quantitative PCR analyses as well as high-throughput Illumina MiSeq amplicon sequencing of bacterial 16S rRNA genes (V3 region via primers 341F/534R).