Welte Cornelia, Deppenmeier Uwe
Institute of Microbiology and Biotechnology, University of Bonn, Bonn, Germany.
Methods Enzymol. 2011;494:257-80. doi: 10.1016/B978-0-12-385112-3.00013-5.
Methanogenic archaea of the genus Methanosarcina possess a unique type of metabolism because they use H(2)+CO(2), methylated C(1)-compounds, or acetate as energy and carbon source for growth. The process of methanogenesis is fundamental for the global carbon cycle and represents the terminal step in the anaerobic breakdown of organic matter in freshwater sediments. Moreover, methane is an important greenhouse gas that directly contributes to climate change and global warming. Methanosarcina species convert the aforementioned substrates to CH(4) via the CO(2)-reducing, the methylotrophic, or the aceticlastic pathway. All methanogenic processes finally result in the oxidation of two thiol-containing cofactors (HS-CoM and HS-CoB), leading to the formation of the so-called heterodisulfide (CoM-S-S-CoB) that contains an intermolecular disulfide bridge. This molecule functions as the terminal electron acceptor of a branched respiratory chain. Molecular hydrogen, reduced coenzyme F(420), or reduced ferredoxin are used as electron donors. The key enzymes of the respiratory chain (Ech hydrogenase, F(420)-nonreducing hydrogenase, F(420)H(2) dehydrogenase, and heterodisulfide reductase) couple the redox reactions to proton translocation across the cytoplasmic membrane. The resulting electrochemical proton gradient is the driving force for ATP synthesis. Here, we describe the methods and techniques of how to analyze electron transfer reactions, the process of proton translocation, and the formation of ATP.
甲烷八叠球菌属的产甲烷古菌具有独特的代谢类型，因为它们利用H₂+CO₂、甲基化的C₁化合物或乙酸盐作为生长的能量和碳源。甲烷生成过程是全球碳循环的基础，代表了淡水沉积物中有机物厌氧分解的最后一步。此外，甲烷是一种重要的温室气体，直接导致气候变化和全球变暖。甲烷八叠球菌通过CO₂还原途径、甲基营养途径或乙酸裂解途径将上述底物转化为CH₄。所有产甲烷过程最终都会导致两种含硫醇的辅因子（HS-CoM和HS-CoB）被氧化，从而形成含有分子间二硫键的所谓异二硫化物（CoM-S-S-CoB）。该分子作为分支呼吸链的末端电子受体。分子氢、还原型辅酶F₄₂₀或还原型铁氧还蛋白用作电子供体。呼吸链的关键酶（Ech氢化酶、不还原F₄₂₀的氢化酶、F₄₂₀H₂脱氢酶和异二硫化物还原酶）将氧化还原反应与质子跨细胞质膜的转运偶联起来。由此产生的电化学质子梯度是ATP合成的驱动力。在这里，我们描述了如何分析电子转移反应、质子转运过程和ATP形成的方法和技术。
