Development of molecular tools for bifidobacterium species

益生菌和益生元产品作为“生活质量和管理生物资源”，以牛奶饮料、酸奶和胶囊的形式出现在市场上。益生菌的摄入与人类和动物宿主的有益健康益处有关，但目前对细菌如何实际产生这些影响的理解不是很好。虽然存在更常见的乳制品乳酸菌如乳球菌和乳杆菌的遗传学和分子工具，但缺乏与密切相关的双歧杆菌属的知识，双歧杆菌属在遗传学和生理学上（双歧杆菌分流）不同。在阐明了分子工具和机制之后，可能会有一种更合理的方法来治疗益生菌的使用。我的研究计划目前的重点是集中在一个假设，即人们可以研究基础科学知识，并通过遗传操作其某些蛋白质的表达来提高益生菌菌株的性能。随着遗传工具的出现，可以做更多的工作来了解它们的生理和代谢活动，这些活动对于在食物中生存以及了解它们在胃肠道系统中的有益作用至关重要。近期目标是（1）开发食品级克隆和表达系统，（2）构建新的过表达系统用于生产胆盐水解酶（BSH）等异源蛋白，以验证BSH假说，从而证实乳酸双歧杆菌菌株的胆固醇降低作用（BSH突变体，天然的和过表达的）在母鸡和小鼠模型中，和3）证明了通过在各自的BSH阴性突变体中克隆感兴趣的基因可以改善益生菌菌株的性能的假设。作为一种耐空气和酸的工业菌株，乳酸双歧杆菌被明确鉴定为目前用于益生菌酸奶中的益生菌性状，这提出了一个挑战，因为很少有基因表达工作已经完成。开发创新的双歧杆菌食品级载体和表达系统以促进我们对代谢活性、基因功能和表达的理解的概念是一个新奇，将有助于研究人员和工业界评估益生菌的作用。

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.