Probiotic mechanisms of Lactobacillus in metal detoxification

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，以隔离它们暴露在环境中的重金属。背景和目标。乳酸杆菌是革兰氏阳性兼性厌氧或嗜微气杆状细菌，在生产一系列食品中使用，包括酸奶、奶酪、酸菜和泡菜，以及动物饲料的青贮饲料。在180种左右的乳杆菌中，干酪乳杆菌和鼠李糖乳杆菌尤其令人感兴趣，因为它们在发酵食品中无处不在，而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应对已知污染食物链和肠道的重金属的存在。我们发现，汞的隔离和解毒确实发生在乳酸菌中，并且似乎与酪氨酸乳杆菌DN114-226中参与半胱氨酸代谢的三基因反向反式硫化途径有关。我们还发现，在亚抑制性汞浓度下培养后，鼠李糖乳杆菌dn116 -060可诱导对汞的抗性；在Hg2+环境中生长，乳酸菌生长滞后期缩短，最低抑菌浓度提高。筛选发现只有这个菌株和另一个相关的鼠李糖L. rhamnosus菌株具有罕见的水平获得的元素，编码最小的抗汞操纵子，通过挥发金属赋予对汞的诱导抗性。研究目的和目的我们计划的目的是了解乳酸杆菌如何作为重金属解毒剂。这个为期五年的项目每年为两名研究生设计，有三个目标：1。验证在主动和被动抗汞和解毒中起作用的遗传因素。2. 确定接触汞如何影响鼠李糖DN116-060的功能在老鼠模型中测试这个概念。以鼠李糖乳杆菌DN116-060、干酪乳杆菌DN114-226和益生菌鼠李糖GR-1为对照和基因受体，由于它们在食物中的繁殖能力和感兴趣的特性，我们将采用敲除和基因插入来优化乳酸菌与汞的结合能力。我们将进行研究，以深入了解这些作用的机制，包括改变乳酸菌的遗传和表面特性，分别改变汞的主动被动封存，并进行转录组学分析以了解其功能。细胞培养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，仍然是一个令人担忧的问题。如果可利用有益细菌减少食物对汞的吸附，就可能对发病率和死亡率产生影响。

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.