Dietary lead modulates the mouse intestinal microbiome: Subacute exposure to lead acetate and lead contaminated soil

The effect of dietary lead on the intestinal microbiome has not been fully elucidated. To determine if there was an association between microflora modulation, predicted functional genes, and Pb exposure, mice were provided diets amended with increasing concentrations of a single lead compound, lead acetate, or a well characterized complex reference soil containing lead, i.e. 6.25-25 mg/kg Pb acetate (PbOAc) or 7.5-30 mg/kg Pb in reference soil SRM 2710a having 0.552 % Pb among other heavy metals such as Cd. Feces and ceca were collected following 9 days of treatment and the microbiome analyzed by 16 S rRNA gene sequencing. Treatment effects on the microbiome were observed in both feces and ceca of mice. Changes in the cecal microbiomes of mice fed Pb as Pb acetate or as a constituent in SRM 2710a were statistically different except for a few exceptions regardless of dietary source. This was accompanied by increased average abundance of functional genes associated with metal resistance, including those related to siderophore synthesis and arsenic and/or mercury detoxification. Akkermansia, a common gut bacterium, was the highest ranked species in control microbiomes whereas Lactobacillus ranked highest in treated mice. Firmicutes/Bacteroidetes ratios in the ceca of SRM 2710a treated mice increased more than with PbOAc, suggestive of changes in gut microbiome metabolism that promotes obesity. Predicted functional gene average abundance related to carbohydrate, lipid, and/or fatty acid biosynthesis and degradation were greater in the cecal microbiome of SRM 2710a treated mice. Bacilli/Clostridia increased in the ceca of PbOAc treated mice and may be indicative of increased risk of host sepsis. Family Deferribacteraceae also was modulated by PbOAc or SRM 2710a possibly impacting inflammatory response. Understanding the relationship between microbiome composition, predicted functional genes, and Pb concentration, especially in soil, may provide new insights into the utility of various remediation methodologies that minimize dysbiosis and modulate health effects, thus assisting in the selection of an optimal treatment for contaminated sites.