乳酸菌源5-甲基四氢叶酸对肠道微生态调节作用及分子机制研究

叶酸是人体必需的B族维生素，人体自身无法合成，我国居民叶酸缺乏情况严重。由于动植物来源叶酸易降解失活，过量化学合成叶酸具有潜在的不安全性，益生菌来源的叶酸目前极受关注。然而，叶酸对肠道微生态的调节作用目前未见报道。课题组前期研究发现5-甲基四氢叶酸及产生菌株植物乳杆菌LZ227使肠道厚壁菌门菌群增加、丁酸含量增加，对肠道益生作用明显，但其分子机制尚不明确。本研究拟构建LZ227叶酸基因敲除株和回复突变株来进行体外肠道菌群模拟系统试验和动物模型试验；通过宏基因组测序从种水平明确乳酸菌源5-甲基四氢叶酸对肠道菌群尤其对丁酸产生菌的调节，明确其对丁酸生物合成代谢调控的关键功能因子；分析关键代谢产物及其对肠道免疫、肠道营养的影响；全面阐明乳酸菌源5-甲基四氢叶酸对肠道微生态的调节作用与分子机制。项目的实施，将为高产叶酸乳酸菌应用于开发改善肠道微生态的新型食品提供新的思路和理论依据。

Folate is an essential B-group vitamin for human body. Large number of Chinese people are in folate deficiency. Considering the folate from animal and plant sources is easily degradable and excessive synthetic folic acid is potentially unsafe,folate synthesized by probiotics has attracted increascing attentions. However, little is known about how the bacterial biosynthesized fotate regulate intestinal microflora. 5-methyltetrahydrofolate is the active form of folate. We have used an in vitro intestinal microflora simulation system to study the effect of folate on the intestinal flora, and found that 5-methyltetrahydrofolate and its producing strain increased the population of Firmicutes bacteria, as well as the content of butyric acid; however, the specific mechanism of action is still unclear. This project is designed to study the regulation of lactic acid bacteria derived 5-methyltetrahydrofolate on gut microflora and its molecular mechanism. LZ227, a Lactobacillus plantarum strain isolated in our lab, has the capacity of producing high yield 5-methyltetrahydrofolate. L. plantarum LZ227 will used as starting strain to construct knockout mutants of 5-methyltetrahydrofolate synthesis and also revertants, and establish a multi-dimensional experimental system based on the in vitro gut microbiota simulation system and animal model. Metagenomics technology will be applied to clarify the effect of lactic acid bacteria derived 5-methyltetrahydrofolate on intestinal flora at species level, especially its effect on butyric acid producing bacteria; and reveal the key factors regulating butyric acid biosynthesis. We will alsoanalyze the regulation of lactic acid bacteria derived 5-methyltetrahydrofolate on the key intestinal metabolites and their effects on intestinal immunity and nutrition, and finally comprehensively elucidate the molecular mechanism of lactic acid bacteria derived 5-methyltetrahydrofolate on the intestinal microflora. The success of this study will also provide valuable information and theoretical basis for application of the 5-methyltetrahydrofolate producing strain L. plantarum LZ227 in development of novel folate fortified foods.