fhs基因调控瘤胃同型产乙酸菌与产甲烷菌竞争氢的机制研究

Hydrogen (H2) is a common substrate for methane (CH4) emission via ruminal methanogens and for acetate production by homoacetogen. The formyl-H4F synthetase (fhs) gene encoding formyl-H4F synthetase enzyme （FTHFS）is the key gene in the metabolic pathway of CoA/Wood-Ljungdahl pathway of homoacetogen. Our previous study demonstrated that Acetitomaculum ruminis is the predominant homoacetogen in young ruminants. Enhancing the expression and activity of fhs gene to increase H2 utilization ability of A. ruminis and reduce H2 available for methanogen may be a potential target to mitigate CH4 emission. Therefore, this project is aimed to build fhs gene knockout and over-expression strains of A. ruminis using molecular biology technology, to analyze the regulation mechanism of fhs gene on its CoA/Wood-Ljungdahl pathway and H2 utilization. Furthermore, an in vitro cultivation experiment of A. ruminis and Methanobrevibacter ruminantium is used to compare the expression and activities of fhs gene and FTHFS enzyme and other genes and enzymes in CoA/Wood-Ljungdahl pathway, H2 utilization level, metabolites and CH4 production, and expression and activities of key genes and enzymes in the biochemical pathways of methanogenesis, to clarify the competitive mechanism between homoacetogen and methanogen in terms of metabolic pathways and electron transport. This project will contribute to a better understanding of the interaction and competition mechanism within ruminal microorganism, providing new thought and target to reduce enteric CH4 emission and increase energy utilization efficiency.

氢气（H2）是产甲烷菌产甲烷（CH4）和同型产乙酸菌产乙酸的共同底物。fhs是编码同型产乙酸菌Acetyl-CoA/Wood-Ljungdahl氢代谢通路关键酶（FTHFS）的基因。前期研究发现，Acetitomaculum ruminis是优势同型产乙酸菌；强化A. ruminis菌通路中fhs基因活性，在提高其对底物H2利用能力的同时降低产甲烷菌的底物H2供给，可能是CH4减排的有效途径。因此，本项目通过构建fhs基因突变体，在解析其影响H2代谢通路的基础上，对比分析A. ruminis和反刍兽甲烷短杆菌在体外培养过程中H2利用水平、乙酸和CH4产量、fhs基因和FTHFS酶以及CH4生成途径中mcrA基因和关键酶的表达量，阐明fhs基因调控两种菌株在H2亲和利用和碳-氢代谢方面的机制，为更好地理解瘤胃H2利用菌间的竞争互作关系，从而降低CH4排放和提高能量利用效率提供新的思路和靶点

氢气（H2）是产甲烷菌产甲烷（CH4）和同型产乙酸菌产乙酸的共同底物。fhs是编码同型产乙酸菌Acetyl-CoA/Wood-Ljungdahl氢代谢通路关键酶（FTHFS）的基因。在前期研究的基础上，通过构建fhs基因突变体和对A. ruminis和反刍兽甲烷短杆菌在体外培养过程中发现，甲烷菌对H2的利用程度显著下降，乙酸和CH4产量的显著降低，而通过测定fhs基因和FTHFS酶以及CH4生成途径中mcrA基因和关键酶的表达量，发现产甲烷菌的代谢途径受到了抑制，从而调控了甲烷菌对瘤胃H2的利用程度。本研究为进一步调控瘤胃发酵模式，挥发性脂肪酸在瘤胃内的利用提供了新的思路。