Structure and Functional Attributes of Bacterial Communities in Premise Plumbing Across the United States

Microbes
that thrive in premise plumbing can have potentially important
effects on human health. Yet, how and why plumbing-associated microbial
communities vary across broad spatial scales remain undetermined.
We characterized the bacterial communities in 496 showerheads collected
from across the continental United States. The overall community structure,
determined by 16S rRNA gene amplicon sequencing, revealed high levels
of bacterial diversity. Although a large fraction of the observed
variation in community composition could not be explained, differences
in bacterial community composition were associated with water supply
(private well water vs public municipal water), water source (groundwater
vs surface water), and associated differences in water chemistry (pH
and chlorine). Most notably, showerheads in homes supplied with public
water had higher abundances of Blastomonas, Mycobacterium, and Porphyrobacter, while Pseudorhodoplanes, Novosphingobium, and Nitrospira were more abundant in those receiving
private well water. We conducted shotgun metagenomic analyses on 92
of these samples to assess differences in genomic attributes. Public
water-sourced showerheads had communities enriched in genes related
to lipid and xenobiotic metabolisms, virulence factors, and antibiotic
resistance. In contrast, genes associated with oxidative stress and
membrane transporters were over-represented in communities from private
well water-sourced showerheads compared to those supplied by public
water systems. These results highlight the broad diversity of bacteria
found in premise plumbing across the United States and the role of
the water source and treatment in shaping the microbial community
structure and functional potential.