Diversity of bile salt hydrolase activities in different lactobacilli toward human bile salts

This study was conducted to evaluate the diversity of bile salt hydrolase (BSH) activities in eight species of lactobacilli. BSH activities were quantified based on the amount of taurine or glycine liberated from six main human bile sodium salts [glycocholic, glycodeoxycholic, glycochenodeoxycholic, taurocholic (TC), taurochenodeoxycholic, taurodeoxycholic] and a mixture of bile salts that resembled human bile. The eight species differed in their BSH activities. Specifically, Lactobacillus helveticus , Lactobacillus fermentum and Lactobacillus gallinarum had the ability to deconjugate taurine-conjugated bile salts, but not glycine-conjugated bile salts, which suggested that microbial BSHs recognize bile salts on both the cholate steroid nucleus and the amino acid moiety. Of the eight species evaluated, Lactobacillus acidophilus strains exhibited the highest specific BSH activity toward human bile salts, with the exception of TC. In addition, the L. acidophilus specific BSH activity toward glycine-conjugated bile salts was ten times higher than that toward taurine-conjugated bile salts. Moreover, the specific BSH activity of Lactobacillus plantarum did not vary significantly toward different bile salts, and Lactobacillus gasseri Am1 exhibited higher specific BSH activity toward TC than other lactobacilli. A comparison of bsh genes indicated that the LA- bshA , LA- bshB , LG- bsh and LP- bsh1 genes that encode the BSH enzymes are highly homologous (higher than 45%), while the LP- bsh2 , LP- bsh3 and LP- bsh 4 genes, which might not encode BSH enzymes, had lower similarity (lower than 26.3%).