A study finds that the enzymes in probiotic bacteria that act on bile salts in the gastrointestinal (GI) tract govern growth of the bacteria. Bile salts in the GI tract promote digestion, but their toxicity to bacteria make them antimicrobial agents. Bacteria living in the GI tract have developed mechanisms to modify and detoxify bile salts. Rodolphe Barrangou, Casey Theriot, and colleagues genetically and biochemically characterized the bile salt hydrolase enzymes produced by two probiotic bacterial species, Lactobacillus acidophilus and Lactobacillus gasseri. The authors found that common bile salts had varying levels of toxicity to Lactobacillus bacteria, but that the degree of toxicity was not limited to chemical structure, given that structural elements of the bile salts did not predict their toxic effects. Further, the authors found that the relationship between bile salt hydrolase activity and fitness of Lactobacillus in the GI tract was dependent on which bile salts were present. Additionally, bile salt hydrolases affected competition between bacterial species, shaping the gut bacterial ecosystem. According to the authors, the results provide a framework to improve the resistance of probiotics to bile salts and boost therapeutic effects on the health of the host and its resident GI tract microbiota.
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Article #20-17709: "Lactobacillus bile salt hydrolase substrate specificity governs bacterial fitness and host colonization," by Matthew H. Foley et al.
MEDIA CONTACT: Rodolphe Barrangou, North Carolina State University, Raleigh, NC; tel: 919-513-1644, 919-917-3105; email: < rbarran@ncsu.edu >
Proceedings of the National Academy of Sciences