This study presents, for the first time, the impact of acrolein, a highly reactive and toxic compound, whose formation is likely a common feature of human gut microbiota, on model intestinal microbial communities.

Glycerol/diol dehydratases (GDH) are bacterial enzymes that catalyze the production acrolein from glycerol. Acrolein is a reactive toxicant compound, which conjugates with dietary carcinogenic heterocyclic amines (HCAs) to reduce mutagenicity, but it is also a wide-spectrum antimicrobial that can impact microbiota activity and composition. Gut microbial GDH activity has been recently suggested as an endogenous acrolein source, however, there is no information on the potential of the intestinal microbiota for GDH activity and therefore acrolein production. We hypothesized that GDH activity of gut microbiota is determined by the abundance and distribution of GDH-active taxa and can be enhanced by supplementation of the GDH-active Anaerobutyricum hallii. We tested this hypothesis combining quantitative profiling of gdh abundance and distribution, and model batch fermentations. Our results suggest that GDH activity is a common trait of intestinal microbiota, which depends on abundance and distribution of contributing taxa. Our findings identified A. hallii as a key taxon in GDH metabolism, with its supplementation increasing the transformation of dietary carcinogens through the release of acrolein. The findings in this study suggest the potential to modulate intestinal GDH activity through dietary and microbial modulation, which may impact endogenous acrolein formation.