Bile salt hydrolase (BSH), a probiotic-related enzyme with cholesterol-assimilating and anti-hypercholesterolemic abilities, has been isolated from intestinal bacteria; however, BSH activity of bacteria in bile-salt-free (non-intestinal) environments is largely unknown. Here, we aimed to identify BSH from non-intestinal Enterococcus faecium and characterize its enzymatic function. We successfully isolated a plasmid-encoded bsh (efpBSH) from E. faecium, and the recombinant EfpBSH showed BSH activity that preferentially hydrolyzed taurine-conjugated bile salts, unlike the activity of known BSHs. EfpBSH functioned optimally at pH 4.0 and 50 °C. EfpBSH exhibited very low amino acid sequence similarity (48.46%) to EfBSH from E. faecalis T2 isolated from human urine, although 241 sequences with 100% identity to EfpBSH were found in both plasmids and chromosomes of E. faecium strains inhabiting intestinal and non-intestinal environments. Phylogenetically, EfpBSH was not affiliated with any known BSH phylogroup and was clearly distinguished from previously identified BSHs from intestinal lactic acid bacteria. Our genome database analysis demonstrated that horizontal gene transfer causes global efpBSH distribution among E. faecium strains in various environments (soil, water, and intestinal samples) and geographical regions (Asia, Africa, Europe, North America, South America, and Australia/Oceania). Overall, our findings are the first to indicate that BSH is not an intestine-specific enzyme and that hitherto-overlooked probiotic candidates with BSH activity can exist in diverse environments.
Keywords: Enterococcus faecium; bile salt hydrolase; horizontal gene transfer; plasmid; probiotics.