Liu Ying, An Haoran, Zhang Jingsheng, Zhou Hui, Ren Fazheng, Hao Yanling
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.
FEMS Microbiol Lett. 2014 Nov;360(2):167-73. doi: 10.1111/1574-6968.12601. Epub 2014 Oct 21.
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.
双歧杆菌是人类肠道的正常寄居菌，其成员通常被认为是益生菌。在发挥其有益特性之前，它们必须在肠道中胆汁的生理浓度（0.05 - 2%）下存活并持续存在。在这项研究中，测试了来自长双歧杆菌BBMN68的编码溶血素样蛋白的tlyC1在胆汁耐受性中的功能作用。使用TMHMM程序和同源比对分析表明，TlyC1是一种非转运膜蛋白，在许多双歧杆菌中保守。tlyC1在乳酸乳球菌NZ9000中的异源表达显示出对0.15%牛胆汁的耐受性提高了45倍。值得注意的是，重组菌株在暴露于亚致死浓度的TCA和TDCA时存活率提高了三倍，而在暴露于GCA和GDCA时未观察到显著变化。此外，实时定量PCR表明，在暴露于亚致死浓度的TCA和TDCA时，长双歧杆菌BBMN68中tlyC1的转录上调了约2.5倍和2.7倍，而在GCA和GDCA刺激下未观察到显著变化。这项研究表明，tlyC1由牛磺结合物特异性诱导，这提供了对牛磺胆酸钠和牛磺脱氧胆酸钠的增强抗性。
