Comparative analysis of aceticlastic methanogenesis in Methanosarcina and Methanosaeta species

地球上产甲烷的主要来源是乙酸甲酯，但只有Methanosarcina （Ms.）和Methanosaeta （Mt.）属能够利用乙酸进行产甲烷和生长。这些属的成员对沼气工厂的生产力也很重要。Methanosaeta sp.的膜结合电子传递系统和能量保存机制在很大程度上是未知的。即使有了嗜热Mt.基因组序列的知识，也无法解释醋酸的利用如何导致ATP的净合成。该项目的总体目标是比较马泽伊女士和嗜热山的醋酸酯利用情况。主题包括醋酸摄取的机制和乙酰辅酶a合成酶的功能。同样重要的是来自嗜热Mt.的焦磷酸酶，它将被分析关于腺嘌呤核苷酸可能的调节作用。此外，我们将分析在醋酸活化过程中产生的焦磷酸盐是否被用于热嗜菌的节能。该菌只含有F420H2脱氢酶和异二硫还原酶的基因。在甲烷藻物种中发现的所有其他节能氧化还原酶明显缺失。还不清楚还原的铁氧还蛋白的电子是如何转移到呼吸链中进行异二硫还原的。为了阐明这些问题，我们想详细分析这种生物的电子传递链。

The major part of methane production on earth originates from the methyl group of acetate, but only the genera Methanosarcina (Ms.) and Methanosaeta (Mt.) are able to use acetate for methanogenesis and growth. Members of these genera are also of great importance for the productivity of biogas plants. The membrane-bound electron transport system and the energy conserving mechanism of Methanosaeta sp. are largely unknown. Even with the knowledge from the genome sequence of Mt. thermophila it cannot be explained how the utilization of acetate leads to a net synthesis of ATP. The overall goal of this project will be the comparison of acetate utilization in Ms. mazei and Mt. thermophila. The topics include the mechanism of acetate uptake and the function of the acetyl-CoA synthetases. Also of central importance is the pyrophosphatase from Mt. thermophila, which will be analysed with respect to possible regulatory effect of adenine nucleotides. In addition, we will analyze whether pyrophosphate, which is produced in the course of acetate activation, is used for energy conservation in Mt. thermophila. This organism only contains gene for the production of the F420H2 dehydrogenase and the heterodisulfide reductase. All other energy conserving oxidoreductases found in Methanosarcina species are obviously missing. It is also unclear how electrons from reduced ferredoxin are transferred into the respiratory chain for heterodisulfide reduction. To shed light on these issues we would like to analyze the electron transport chain of this organism in detail.