Molecular insight into bacterial communities of consumer tap water – a case study

Abstract

The issue of consumer tap water (i.e., tap water collected without prior flushing – as drawn by consumers from household taps) is often neglected in scientific reports concerning drinking water microbiology. Although water companies usually provide water that is safe to drink, its microbial quality could significantly deteriorate within a building. In this study, four samples collected from taps assembled close to each other within the same building were compared in terms of bacterial community composition, biodiversity, and 16S rRNA gene-denaturing gradient gel electrophoresis and resistome profiling. The results revealed high diversity of samples, indicating the impact of premise plumbing or taps on the microbiome of consumer tap water. All detected bacteria belonged to the phyla Proteobacteria, Firmicutes and Bacteroidetes. However, neither common bacterial core nor resistome was determined among the investigated samples. Each sample presented a unique bacterial community. These results suggest that bacteria dwelling in premise plumbing or taps shape the microbiome of consumer tap water, masking the microorganisms present in tap water provided by a water company. It is known that it is not common practice for consumers to flush tap water before collection. Therefore, consumer health risk could primarily depend on bacteria dwelling in premise plumbing.