title: Bile salt tolerance of Lactococcus lactis is enhanced by expression of bile salt hydrolase thereby producing less bile acid in the cells.
abstract: OBJECTIVE
  Changes of bile salt tolerance, morphology and amount of bile acid within cells were studied to evaluate the exact effects of bile salt hydrolase (BSH) on bile salt tolerance of microorganism.
  
  
  RESULTS
  The effect of BSHs on the bile salt tolerance of Lactococcus lactis was examined by expressing two BSHs (BSH1 and BSH2). Growth of L. lactis expressing BSH1 or BSH2 was better under bile salt stress compared to wild-type L. lactis. As indicated by transmission electron microscopy, bile acids released by the action of BSH induced the formation of micelles around the membrane surface of cells subject to conjugated bile salt stress. A similar micelle containing bile acid was observed in the cytoplasm by liquid chromatography-mass spectrometry. BSH1 produced fewer bile acid micelles in the cytoplasm and achieved better cell growth of L. lactis compared to BSH2.
  
  
  CONCLUSIONS
  Expression of BSH improved bile salt tolerance of L. lactis but excessive production by BSH of bile acid micelles in the cytoplasm inhibited cell growth.
authors.affiliation: Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Lihu Avenue, Wuxi, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Bi
authors.affiliation: Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Lihu Avenue, Wuxi, China.
authors.forename: Song
authors.initials: S
authors.lastname: Liu
authors.affiliation: Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Lihu Avenue, Wuxi, China.|Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Lihu Avenue, Wuxi, China.
authors.forename: Guocheng
authors.initials: G
authors.lastname: Du
authors.affiliation: Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Lihu Avenue, Wuxi, China. jchen@jiangnan.edu.cn.|National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Lihu Avenue, Wuxi, China. jchen@jiangnan.edu.cn.
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
mesh_terms: D000581:Amidohydrolases / Q000235:genetics / Q000378:metabolism*; D001647:Bile Acids and Salts / Q000378:metabolism*; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000737:chemistry; D013294:Lactococcus lactis / Q000235:genetics / Q000254:growth & development*; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D055049:Salt Tolerance
chemical_list: D001647:Bile Acids and Salts; D008823:Micelles; D000581:Amidohydrolases; C023154:choloylglycine hydrolase
keywords: Bile salt hydrolase; Bile salt tolerance; Conjugated bile salt; Lactic acid bacteria; Lactobacillus; Lactococcus