Probiotic mechanisms of Lactobacillus in metal detoxification

乳酸菌在金属解毒中的益生机制

• 批准号: RGPIN-2014-05188
• 负责人: Reid, Gregor
• 金额: $ 2.48万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=630535
• 关键词: Probiotic; mechanisms; Lactobacillus; metal; detoxification

Hypothesis. We hypothesize that members of bacterial genus, Lactobacillus, have developed the ability to acquire specific genetic elements in order to sequester heavy metals to which they are exposed in the environment. Background and Objectives.Lactobacilli are Gram positive facultative anaerobic or microaerophilic rod-shaped bacteria notable for their use in the production of a range of foods, including yogurt, cheese, sauerkraut and pickles as well as silage for animal feed. Of the 180 or so species of Lactobacillus, the L. casei and L. rhamnosus species are of particular interest as they are ubiquitous in fermented foods and a number of strains have proved effective as probiotics. We are intrigued by their adaptability to grow in various foods and survive in conditions within the body and we wondered if they cope with the presence of heavy metals known to contaminate the food chain and the intestine. We have discovered that sequestration and detoxification of mercury does indeed occur in lactobacilli, and appears to be associated with a characterized three-gene reverse trans-sulfuration pathway involved in cysteine metabolism in L. casei DN114-226, We also discovered that resistance to mercury can be induced in L. rhamnosus DN 116-060 after incubation in sub-inhibitory mercury concentrations; the lactobacilli have both a decreased lag growth period and higher minimum inhibitory concentrations when grown in Hg2+. The screening uncovered only this strain, and one other related L. rhamnosus strain possessing a rare horizontally acquired element encoding a minimal mercury resistance operon imparting inducible resistance to mercury by volatilizing the metal. Research aim and objectives The aim of our program is to understand how Lactobacillus acts as a heavy metal detoxifying agent. The five year program designed for two graduate students each year has three objectives:1. Verify the genetic elements that play a role in active and passive mercury resistance and detoxication. 2. Determine how exposure to mercury affects L. rhamnosus DN116-060 functionality 3. Test the concept in a murine model. Using Lactobacillus rhamnosus DN116-060, L. casei DN114-226, and probiotic L. rhamnosus GR-1 as a control and gene recipient, all due to their ability to propagate in food and characteristics of interest, we will use knock-outs and gene insertion to optimize the ability of lactobacilli to bind to mercury. We will perform studies that provide insight into the mechanisms of these actions, including altering genetics and surface properties of lactobacilli to modify the active passive sequestration of mercury, respectively, and doing transcriptomic analysis to understand functionality. A cell culture and mouse model will be used for in vivo experiments. Significance and Future Studies: Heavy metal poisoning is common in certain parts of the world, and here in Canada exposure levels vary and remain a cause for concern. If beneficial bacteria can be utilized to reduce adsorption of mercury through foods, this could have an impact on morbidity and mortality.

假说.我们假设，细菌属，乳酸杆菌，成员已经开发出的能力，以获得特定的遗传元素，以螯合重金属，它们暴露在环境中。背景和目的：乳酸杆菌是革兰氏阳性兼性厌氧或微需氧杆状细菌，以其在生产一系列食品中的应用而闻名，包括酸奶、奶酪、泡菜和泡菜以及动物饲料的青贮饲料。在180种左右的乳杆菌中，L.干酪乳杆菌和L.特别令人感兴趣的是鼠李糖菌种，因为它们在发酵食品中普遍存在，并且许多菌株已被证明是有效的益生菌。我们对它们在各种食物中生长的适应性和在体内条件下的生存感兴趣，我们想知道它们是否科普已知污染食物链和肠道的重金属的存在。我们发现，汞的螯合和解毒确实发生在乳酸杆菌中，并且似乎与乳酸杆菌中参与半胱氨酸代谢的特征性三基因反向转硫途径有关。casei DN 114 -226，同时发现L. rhamnosus DN 116-060;当在Hg 2+中生长时，乳杆菌具有减少的滞后生长期和较高的最小抑制浓度。筛选只发现了该菌株，以及另一个相关的L。rhamnosus菌株，其具有编码最小汞抗性操纵子的罕见水平获得元件，该操纵子通过挥发金属赋予对汞的诱导抗性。研究目的和目标我们计划的目的是了解乳酸菌如何作为重金属解毒剂。五年计划设计的两个研究生每年有三个目标：1。验证在主动和被动汞抗性和解毒中发挥作用的遗传因素。2.确定接触汞如何影响L。rhamnosus DN 116 -060功能性在小鼠模型中测试这个概念。以鼠李糖乳杆菌（Lactobacillus rhamnosus）DN 116 -060、L.酪蛋白DN 114 -226和益生菌L.作为对照和基因接受者的鼠李糖乳杆菌GR-1，所有这些都是由于它们在食物中繁殖的能力和感兴趣的特征，我们将使用敲除和基因插入来优化乳杆菌结合汞的能力。我们将进行研究，深入了解这些行动的机制，包括改变乳酸杆菌的遗传和表面特性，分别修改汞的主动被动螯合，并进行转录组学分析，以了解功能。细胞培养物和小鼠模型将用于体内实验。意义和未来研究：重金属中毒在世界某些地区很常见，在加拿大，暴露水平各不相同，仍然令人担忧。如果可以利用有益细菌来减少食物对汞的吸附，这可能会对发病率和死亡率产生影响。