title: Functional role of tlyC1 encoding a hemolysin-like protein from Bifidobacterium longum BBMN68 in bile tolerance.
abstract: Bifidobacteria are normal inhabitants of the human gut, and members of which are generally considered to be probiotic. Before exerting their beneficial properties, they must survive and persist in the physiological concentrations (0.05-2%) of bile in the gut. In this work, the functional role of tlyC1 encoding a hemolysin-like protein from Bifidobacterium longum BBMN68 in bile tolerance was tested. Analysis using the program TMHMM and homologous alignment indicated that TlyC1 is a nontransporter membrane protein and is conserved in many bifidobacteria. Heterologous expression of tlyC1 in Lactococcus lactis NZ9000 was shown to confer 45-fold higher tolerance to 0.15% ox-bile. Notably, the recombinant strains showed threefold higher survival when exposed to sublethal concentration of TCA and TDCA, while no significant change was observed when exposed to GCA and GDCA. Furthermore, real-time quantitative PCR demonstrated that the transcription of tlyC1 was up-regulated c. 2.5- and 2.7-fold in B. longum BBMN68 exposed to sublethal concentration of TCA and TDCA, while no significant change was observed with GCA and GDCA challenges. This study indicated that tlyC1 was specifically induced by tauroconjugates, which provided enhanced resistance to sodium taurocholate and sodium taurodeoxycholate.
authors.affiliation: Key Laboratory of Functional Dairy, Co-constructed by Ministry of Education and Beijing Municipality, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.forename: Haoran
authors.initials: H
authors.lastname: An
authors.forename: Jingsheng
authors.initials: J
authors.lastname: Zhang
authors.forename: Hui
authors.initials: H
authors.lastname: Zhou
authors.forename: Fazheng
authors.initials: F
authors.lastname: Ren
authors.forename: Yanling
authors.initials: Y
authors.lastname: Hao
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001644:Bifidobacterium / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D004361:Drug Tolerance; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D013294:Lactococcus lactis / Q000187:drug effects / Q000235:genetics; D008565:Membrane Proteins / Q000378:metabolism*; D050296:Microbial Viability / Q000187:drug effects; D060888:Real-Time Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000235:genetics; D013656:Taurocholic Acid / Q000633:toxicity*; D013657:Taurodeoxycholic Acid / Q000633:toxicity*
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D011994:Recombinant Proteins; D013657:Taurodeoxycholic Acid; D013656:Taurocholic Acid
keywords: Bifidobacterium longum BBMN68; bile salt tolerance; function analysis; hemolysin-like protein