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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=663150
• 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.

假设。 *我们假设细菌属的成员，乳酸菌，已经发展出获得特定遗传元素的能力，以隔离它们在环境中暴露的重金属。 * *背景和目标。*乳酸杆菌是革兰氏阳性兼性厌氧或微需氧杆状细菌，因其在生产一系列食品中的用途而闻名，包括酸奶、奶酪、泡菜和泡菜以及动物饲料青贮饲料。在 180 种左右的乳杆菌中，干酪乳杆菌和鼠李糖乳杆菌尤其令人感兴趣，因为它们普遍存在于发酵食品中，并且许多菌株已被证明可以作为益生菌发挥作用。我们对它们在各种食物中生长和在体内条件下生存的适应性很感兴趣，我们想知道它们是否能够应对已知会污染食物链和肠道的重金属的存在。我们发现，汞的封存和解毒确实发生在乳酸菌中，并且似乎与干酪乳杆菌 DN114-226 中参与半胱氨酸代谢的特征性三基因逆反式硫化途径有关。我们还发现，对汞的抗性在亚抑制性汞浓度下孵育后，可在鼠李糖乳杆菌 DN 116-060 中诱导；当乳酸菌在 ​​Hg2+ 中生长时，其生长滞后期缩短，最低抑制浓度更高。筛选仅发现了该菌株，以及另一种相关的鼠李糖乳杆菌菌株，其具有罕见的水平获得元件，编码最小的汞抗性操纵子，通过挥发金属赋予对汞的诱导性抗性。 **研究目的和目标 *我们计划的目的是了解乳酸菌如何充当重金属解毒剂。每年为两名研究生设计的五年计划有三个目标：*1。验证在主动和被动汞抵抗和解毒中发挥作用的遗传元件。 *2.确定接触汞如何影响鼠李糖乳杆菌 DN116-060 功能 *3。在小鼠模型中测试这个概念。 **使用鼠李糖乳杆菌 DN116-060、干酪乳杆菌 DN114-226 和益生菌鼠李糖乳杆菌 GR-1 作为对照和基因受体，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性，我们将使用敲击-输出和基因插入以优化乳酸杆菌与汞结合的能力。我们将开展研究，深入了解这些作用的机制，包括改变乳酸杆菌的遗传学和表面特性，以分别改变汞的主动被动封存，并进行转录组分析以了解其功能。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，接触水平各不相同，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。