Coe, Krout, Munro-Ehrlich, Beamish, Vorojeikina, Colman, Boyd, Walk, Rand 2023 — Gut microbiome role in methylmercury demethylation and elimination
This Archives of Toxicology paper from a Montana State University and University of Rochester collaboration assesses whether the human gut microbiome contributes to methylmercury (MeHg) demethylation and fecal elimination, using both a human cohort with paired stool-and-MeHg-exposure data and a gnotobiotic mouse experimental model with human-microbiota colonization. The paper is the first to combine human cohort observation with controlled gnotobiotic experimental confirmation that gut microbial activity is a determinant of host MeHg fate. The findings support the gut-microbiome-mediated demethylation pathway as a contributor to the inter-individual variability in MeHg body burden observed across populations consuming similar dietary MeHg from fish and seafood.
Key conclusions
The gut microbiome demethylates a measurable fraction of ingested methylmercury, with the demethylated inorganic mercury preferentially excreted in feces rather than absorbed systemically. Inter-individual variation in microbiome composition produces inter-individual variation in MeHg demethylation efficiency, which translates to variation in systemic MeHg body burden at equivalent dietary intake. Specific microbial taxa with documented mer operon machinery for organomercury demethylation are associated with higher demethylation efficiency in the human cohort and confirmed in the gnotobiotic mouse arm.
Implications
- Certification: Mechanistic support for population-level rather than individual-level MeHg dietary guidance, since individual demethylation efficiency varies with microbiome composition. The finding does not change the population-level MeHg toxicology floor but explains why simple intake-based exposure assessments produce wide individual variance.
- Microbiome: This is the wiki’s first MeHg-specific microbiome source. Crosswalks to WikiBiome for organomercury demethylation. Closes the previously-flagged MeHg-microbiome data gap. The paper’s mer-operon-bearing taxa are the proposed mechanistic actors.
- Courses: Useful for teaching the gut microbiome as a metal-fate determinant.