Abstract
Lactobacillus gasseri is one of the most likely probiotic candidates among many Lactobacillus species. Although bile salt resistance has been defined as an important criterion for selection of probiotic candidates since it allows probiotic bacteria to survive in the gut, both its capability and its related enzyme, bile salt hydrolase (BSH), in L. gasseri is still largely unknown. Here, we report that the well-known probiotic bacterium L. gasseri JCM1131T possesses BSH activity and bile salt resistance capability. Indeed, this strain apparently showed BSH activity on the plate assay and highly tolerated the primary bile salts and even taurine-conjugated secondary bile salt. We further isolated a putative BSH enzyme (LagBSH) from strain JCM1131T and characterized the enzymatic function. The purified LagBSH protein exhibited quite high deconjugation activity for taurocholic acid and taurochenodeoxycholic acid. The lagBSH gene was constitutively expressed in strain JCM1131T, suggesting that LagBSH likely contributes to bile salt resistance of the strain and may be associated with survival capability of strain JCM1131T within the human intestine by bile detoxification. Thus, this study first demonstrated the bile salt resistance and its responsible enzyme (BSH) activity in strain JCM1131T, which further supports the importance of the typical lactic acid bacterium as probiotics.
Highlights
Lactobacillus species have been considered as one of the major targets of probiotic research
We found the putative bsh gene in the genome and determined that its recombinant protein could functionally act as bile salt hydrolase (BSH) mediating the bile salt resistance in the strain through molecular cloning, biochemical characterization, and transcriptional analyses
We identified that Lactobacillus gasseri JCM1131T displayed bile salt resistance capacity toward primary bile salts and taurine-conjugated secondary bile salt
Summary
Lactobacillus species have been considered as one of the major targets of probiotic research. Several Lactobacillus species provide positive impacts on human health; symptomatic improvements by probiotics have been reported in cases of various hard-to-heal diseases, e.g., allergy [1], diarrhea [2], Helicobacter pylori infection [3], and irritable bowel syndrome [4]. These probiotic effects are generally strain-specific and differ depending on each strain even among Lactobacillus strains of same species [5,6,7,8,9].
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