Molecular mechanisms of exopolysaccharide production by probiotic and lactic acid bacteria

益生菌和乳酸菌产生胞外多糖的分子机制

• 批准号: 183904-2009
• 负责人: LaPointe, Gisèle
• 金额: $ 2.55万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2009
• 资助国家: 加拿大
• 起止时间: 2009-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=422979
• 关键词: Molecular; mechanisms; exopolysaccharide; production; probiotic

The ability of lactic acid bacteria (LAB) to survive and dominate in such diverse anaerobic ecosystems as the intestinal tract and our food can be attributed to competitive advantages such as their fermentative metabolism, which creates acidic conditions not tolerated by all microorganisms. They also compete by excreting other extracellular products such as antimicrobial compounds and exopolysaccharides (EPS). These polymers, which are very diverse in structure, have been attributed a role in protecting the bacterial cell against physical, chemical and biological stresses of the environment. They are important in forming biofilms on substrates and host tissues, in countering predation and avoiding host defence mechanisms, as well as in overcoming pH and nutrient limitations. Surface oligosaccharides of probiotic bacteria may contribute to inhibiting pathogen binding in the gastrointestinal tract, thus preventing infection. The biosynthesis of EPS involves diverting sugar precursors away from glycolysis and sequestering them in an extracellular polymer. The necessity of maintaining a balance between energy production, cell constituents and other endproducts implies a complex regulatory mechanism for exopolysaccharide biosynthesis, thus providing an ideal model system for studying gene regulation and environmental sensing mechanisms. Ultimately, this knowledge can be applied to optimising or selecting novel activities useful to the food industry and to human health. Polysaccharide structure and size modulate their functional activities. Even though advances have been accomplished on the physiology of EPS production, little is known on the regulatory mechanisms for lactic acid and probiotic bacteria. Now that more is known about EPS gene clusters of lactobacilli, lactococci and bifidobacteria through the work of our group, future research will concentrate on the role of growth phase and oxygen in controlling gene expression as well as the polymerisation process itself. Understanding gene regulation and protein function in lactic acid bacteria is essential for improving yogurt and cheese starter microorganisms, as well as for preventing food spoilage and improving human health.

乳酸菌(LAB)在肠道和我们的食物等各种厌氧生态系统中生存并占据主导地位的能力可以归因于竞争优势，例如它们的发酵代谢，这创造了所有微生物都不能容忍的酸性条件。它们还通过分泌其他胞外产物进行竞争，如抗菌化合物和胞外多糖(EPS)。这些聚合物的结构非常多样化，被认为在保护细菌细胞免受环境的物理、化学和生物压力方面发挥了作用。它们对于在底物和宿主组织上形成生物膜、对抗捕食和避免宿主防御机制以及克服pH和营养限制都是重要的。益生菌的表面寡糖可能有助于抑制病原体与胃肠道的结合，从而预防感染。EPS的生物合成包括从糖酵解中转移糖前体，并将它们隔离在胞外聚合物中。在能量生产、细胞成分和其他最终产物之间保持平衡的必要性意味着胞外多糖生物合成的复杂调控机制，从而为研究基因调控和环境感知机制提供了理想的模型系统。最终，这些知识可以应用于优化或选择对食品工业和人类健康有用的新活动。多糖的结构和大小调节其功能活性。尽管在EPS产生的生理学方面已经取得了进展，但对乳酸和益生菌的调节机制知之甚少。现在，通过我们小组的工作，人们对乳杆菌、乳球菌和双歧杆菌的EPS基因簇有了更多的了解，未来的研究将集中在生长阶段和氧气在控制基因表达方面的作用以及聚合过程本身。了解乳酸菌的基因调控和蛋白质功能对于改良酸奶和奶酪发酵剂微生物，防止食品变质和改善人类健康至关重要。