Diversity of genes involved in the metabolism of gallic acid, a dietary component, within the human gut microbiota

Abstract

The human gut microbiota contains a broad variety of bacteria that possess functional genes, and resultant metabolites, which affect human physiology and, therefore, health. Dietary gallates are phenolic components present in many foods and beverages, and are regarded as having health promoting attributes. However, the fate of these phenolic compounds by the human microbiota is unknown. The emergence of high-throughput DNA sequencing (HTS) technologies allowed to get insights into the functional potential of the gut microbiota on the in vivo occurrence of metabolites formed via enzymatic degradation. In this study, HTS was used to assess the incidence of gallate decarboxylating bacteria in healthy human microbiota. Degenerate primers were designed to amplify a region encoding the catalytic C subunit of gallate decarboxylase from total metagenomic DNA extracted from human faecal samples. HTS resulted in the generation of a total of 3,261,967 sequence reads and revealed that the primary gallate-decarboxylating microbial phyla in the intestinal microbiota are Firmicutes (74.6%), Proteobacteria (17.6%), and Actinobacteria (7.8%). These reads corresponded to fifty-three genera, indicating that these genes are present in 47% of the bacterial genera present in these samples. At the genus level, Anaerostipes and Klebsiella accounted for the majority of reads (40%) followed by Lachnospiraceae, Dorea, Clostridium, Blautiaand Actynomyces. The alignment of C subunit sequences revealed a heterogeneity of identity (24 to 99%) with a high level of conservation among non-related encoding genera. Ultimately, this study allowed the identification of human intestinal microbes encoding gallate decarboxylase genes.