We expect people next door to be good citizens and would like to meet them before moving in. When it comes to the neighbors living in our tap water, precaution is especially in order. In the “Microbial Neighbors in your Tap Water” series, our PLoS ONE paper released today introduces these invisible neighbors- the building plumbing microbiome- and examines the factors that shape their “neighborhoods”.
Like people, microbial neighbors can be highly individualistic and picky (i.e., fastidious), making it hard to figure out why they “choose” to live in certain neighborhoods. To help figure this out, we installed and studied identical pipe rigs that simulate a home by having the water sit (i.e., when sleeping or at work) and flow (i.e., morning shower or dinner time) over 8 hour cycles at five U.S. water utilities. We found that the location of the water utility (including influent water properties and water treatment processes) had an overarching effect on both water chemistry and microbiome composition, while water age (0.6-6.5 days), 8-hr stagnation, and pipe materials had more subtle effects. Further, a paired comparison of two utilities that happened to draw from the same source water indicated that differences in water treatment and distribution can also influence the composition of the microbiome at the tap. To consider just how picky some microbes are about where they live, we conducted a core microbiome analysis. About ~20-50% of the microbe identified would live just about anywhere, a group we refer to as the “universal core” (OTUs found at all sites). A somewhat pickier group, the “specific core,” were found in all of the locations of one utlility site, but not the other utilities, consisted of >30% total microbiome at all but one site. Analysis of water chemistry data suggested that total chlorine concentration, pH, P, SO42- and Mg were most associated with patterns in microbiome composition patterns. This provides clues about why some microbes live where they do.
We hope to release a second episode soon, where we will explore the possibility of you “selecting” the microbial neighbors living in your tap for yourself. Stay tuned.