Novel autotrophic CO2 fixation pathways in Bacteria and Archaea

目前已知有七种不同的自养途径，可能还有更多的途径存在，等待它们的描述。此外，这些途径的变体可能具有非常不同的特性。在第一个资助期，我们展示了自养硫还原Desulfurellaceae使用rTCA循环的变体，柠檬酸合酶在相反方向上操作，这在生理条件下被认为是不可能的反应。这种被忽视的能量高效碳固定途径是由二氧化碳的高分压驱动的。在自养古细菌中，我们可以确定一些酶在医院Ignicoccus hospitalis， Metallosphaera seula和Nitrosopumilus maritimus中参与自养。在接下来的三年中，我们将进一步解决有关细菌和古细菌自养的几个开放性问题。本研究的主要目的是研究P. arsenaticum和P. aerophilum以及Desulfovibrionaceae科不同成员的自养CO2固定，并提出了不同的CO2固定途径。此外，我们将在M. sedula （Crenarchaeaota）和氨氧化古菌中鉴定和表征尚未鉴定的羟丙酸/羟丁酸循环的特异性酶，这些古菌使用不同的羟丙酸/羟丁酸循环，并研究F420在其中的作用。

Seven different autotrophic pathways are known today, and further pathways may exist and are awaiting their description. Furthermore, there are variants of the pathways that may have very different properties. In the first funding period we showed that autotrophic sulfur-reducing Desulfurellaceae use a variant of the rTCA cycle with citrate synthase operating in the reverse direction, a reaction that was regarded impossible under physiological conditions. This overlooked energetically efficient carbon fixation pathway is driven by high partial pressures of CO2. In autotrophic Archaea, we could characterize a number of enzymes that are involved in autotrophy in Ignicoccus hospitalis, Metallosphaera sedula and Nitrosopumilus maritimus. In the subsequent three years, we are going to further address several open questions concerning autotrophy in Bacteria and Archaea. The main goals of the proposal are the study of autotrophic CO2 fixation in P. arsenaticum and P. aerophilum as well as in different members of Desulfovibrionaceae family, which were proposed to use different CO2 fixation pathways. In addition, we are going to identify and characterize yet unidentified specific enzymes of the hydroxypropionate/hydroxybutyrate cycle in M. sedula (Crenarchaeaota) and in ammonia-oxidizing archaea that are using different variants of the hydroxypropionate/ hydroxybutyrate cycle as well as to investigate the role of F420 therein.