Development of molecular tools for bifidobacterium species

作为“生活质量和管理生物资源”的益生菌和益生菌产品以牛奶饮料、酸奶和胶囊的形式在市场上上市。摄取益生菌对人类和动物宿主的健康有益，但目前对细菌实际上是如何使这些影响非法的了解并不是很好。虽然乳酸菌和乳杆菌等常见乳酸菌的遗传学和分子工具已经存在，但与双歧杆菌属亲缘关系密切的双歧杆菌属缺乏相关知识，双歧杆菌属在系统发育和生理上(双歧分流)截然不同。在阐明了益生菌的分子工具和机制后，可能会有一种更合理的方法来治疗益生菌。我目前的研究计划的重点是这样一个假设，即一个人可以学习基础科学知识，并通过遗传操作某些蛋白质的表达来改善益生菌菌株的性能。随着双歧杆菌的遗传工具的出现，可以做更多的工作来了解它们的生理和代谢活动对食物中的生存至关重要，以及了解它们在胃肠道系统中的有益影响。短期目标是(1)开发食品级克隆和表达系统，(2)构建新的过表达系统来生产像胆盐水解酶(BSH)这样的异源蛋白，以验证BSH假说对乳酸双歧杆菌(BSH突变体，天然和过表达)在母鸡和小鼠模型中的降胆固醇作用，以及(3)证明人们可以通过克隆BSH阴性突变体中的相关基因来改善益生菌菌株的性能的假说。乳酸双歧杆菌是一种耐空气和耐酸的工业菌株，显然是目前在益生菌酸奶中使用的益生菌特性，这是一个挑战，因为人们所做的遗传表达工作很少。开发创新的食品级双歧杆菌载体和表达系统，以促进我们对双歧杆菌代谢活性、基因功能和表达的了解，这是一项新颖的概念，将有助于研究人员和行业评估益生菌的效果。

Probiotic and prebiotic products as "quality of life and managing biological resources" are on the market in the forms of milk based drinks, yogurts and capsules. Intake of probiotic bacteria is associated with beneficial health benefits to the human and animal hosts, but current understanding of how the bacteria actually illicit these effects is not very good. Although the genetics and molecular tools of more common dairy lactic bacteria like Lactococcus and Lactobacillus exist, knowledge is lacking behind with closely related Bifidobacterium genus, which is phylogenetically and physiologically (bifidus shunt) distinct. After the molecular tools and mechanisms are elucidated, a more rational approach to the therapeutic use of probiotics could be possible. The current focus of my research program is centered on the hypothesis that one can study fundamental scientific knowledge and improve the performance of probiotic strain by genetic manipulation of its expression of certain proteins. As genetic tools become available for bifidobacteria, more work can be done on understanding their physiology and metabolic activities important for survival in food as well as for understanding their beneficial effects in the gastrointestinal system. The short term objectives are to (1) develop food grade cloning and expression systems, (2) construct new over-expression systems for production of a heterologous protein like bile salt hydrolase (BSH) to validate BSH hypothesis for cholesterol lowering effect of Bifidoabcterium lactis strains (BSH mutant, native and over-expressed) in hens and mice models, and 3) demonstrate the hypothesis that one can improve the performance of probiotic strains by cloning the genes of interest in the respective BSH negative mutants. An air and acid tolerant industrial strain, Bifidobacterium lactis clearly identified as probiotic traits that currently used in probiotic yogurts and this presents a challenge as very little genetic expression work has been done. The concept of developing an innovative Bifidobacterium food-grade vector and expression system to advance our understanding of the metabolic activity, gene function, and expression is a novelty that will be useful for researcher and industries to evaluate the probiotic effects.