Exposure to chlorinated drinking water alters the murine fecal microbiota

An abundant body of scientific studies and regulatory guidelines substantiates antimicrobial efficacy of freshwater chlorination ensuring drinking water safety in large populations worldwide. In contrast to the purposeful use of chlorination ensuring antimicrobial safety of drinking water, only a limited body of research has addressed the molecular impact of chlorinated drinking water exposure on the gut microbiota. Here, for the first time, we have examined the differential effects of drinking water regimens stratified by chlorination agent [inorganic (HOCl) versus chloramine (TCIC)] on the C57BL/6J murine fecal microbiota. To this end, we exposed C57BL/6J mice to chlorinated drinking water regimens followed by fecal bacterial microbiota analysis at the end of the three-week feeding period employing 16S rRNA sequencing. α-diversity was strongly reduced when comparing chlorinated versus control drinking water groups and community dissimilarities (β-diversity) were significant between groups even when comparing HOCl and TCIC. We detected significant differences in fecal bacterial composition as a function of drinking water chlorination observable at the phylum and genus levels. Differential abundance analysis of select amplicon sequence variants (ASVs) revealed changes as a function of chlorination exposure [up: Lactobacillus ASV1; Akkermansia muciniphila ASV7; Clostridium ss1 ASV10; down: Ileibacterium valens ASV5; Desulfovibrio ASV11; Lachnospiraceae UCG-006 ASV15]. Given the established complexity of murine and human gastrointestinal microbiota and their role in health and disease, the translational relevance of the chlorination-induced changes documented by us for the first time in the fecal murine microbiota remains to be explored.