Identifying a Novel Bile Salt Hydrolase from the Keystone Gut Bacterium .

are human gut dwelling bacteria that have been proposed as key members of the gut microbiome, regulating energy balance and adiposity of their host. We formerly identified that a novel strain of (strain DSM33407) boosted microbiota diversity and stimulated deconjugation of the primary bile acid taurocholic acid in human samples. However, there is no description of a bile salt hydrolase (BSH) protein carried in the genome of . Here, we identified and cloned a protein from genome that carries a potent BSH activity, which preferentially deconjugates glycine-conjugated bile acids. We then retrieved 14,319 putative BSH sequences from the NCBI database and filtered them using the UHGP database to collect a total of 6701 sequences that were used to build the most comprehensive phylogenetic tree of BSH-related enzymes identified in the human microbiome so far. This phylogenetic tree revealed that BSH amino acid sequence clusters away from others with a threshold of 70% identity. This is therefore the first description of BSH protein, which may be involved in its unique role within the human gut microbial ecosystem.