Department of Pharmaceutical Sciences, University of Bologna, Italy.
Department of Pathological Anatomy Martinelli, S. Orsola-Malpighi, University of Bologna, Italy.
Microbiology (Reading). 2010 Jun;156(Pt 6):1609-1618. doi: 10.1099/mic.0.038307-0. Epub 2010 Feb 18.
Bifidobacterium animalis subsp. lactis lives in the gastrointestinal tract of most mammals, including humans. Recently, for the probiotic strain B. animalis subsp. lactis BI07, a dose-dependent plasminogen-binding activity was demonstrated and five putative plasminogen-binding proteins were identified. Here we investigated the role of surface DnaK as a B. animalis subsp. lactis BI07 plasminogen receptor. DnaK was visualized on the bacterial cell surface by transmission electron microscopy. The His-tagged recombinant DnaK protein showed a high affinity for human plasminogen, with an equilibrium dissociation constant in the nanomolar range. The capability to tolerate physiological concentrations of bile salts is a crucial feature for an intestinal symbiont micro-organism. By proteome analysis we demonstrated that the long-term exposure of B. animalis subsp. lactis BI07 to bile salts results in the upregulation of important surface plasminogen receptors such as DnaK and enolase. Moreover, adaptation of B. animalis subsp. lactis BI07 to physiological concentrations of bile salts significantly increased its capacity to interact with the host plasminogen system. By enhancing the bacterial capacity to interact with the host plasminogen, the gut bile environment may facilitate the colonization of the human host by B. animalis subsp. lactis BI07.
动物双歧杆菌亚种。乳生活在大多数哺乳动物的胃肠道中，包括人类。最近，对于益生菌菌株 B. animalis subsp。乳 BI07，证明了剂量依赖性纤溶酶原结合活性，并鉴定了五个假定的纤溶酶原结合蛋白。在这里，我们研究了表面 DnaK 作为 B. animalis subsp。乳 BI07 纤溶酶原受体的作用。通过透射电子显微镜观察到 DnaK 存在于细菌细胞表面。His 标记的重组 DnaK 蛋白与人纤溶酶原具有高亲和力，平衡解离常数在纳摩尔范围内。能够耐受生理浓度的胆汁盐是肠道共生微生物的一个关键特征。通过蛋白质组分析，我们证明了 B. animalis subsp。乳 BI07 长期暴露于胆汁盐会导致重要的表面纤溶酶原受体（如 DnaK 和烯醇酶）上调。此外，B. animalis subsp。乳 BI07 对生理浓度胆汁盐的适应显著增加了其与宿主纤溶酶原系统相互作用的能力。通过增强细菌与宿主纤溶酶原相互作用的能力，肠道胆汁环境可能有助于 B. animalis subsp。乳 BI07 定植于人体宿主。
