Elucidation of new autotrophic CO2 fixation pathways in bacteria

自养是使用二氧化碳（CO2）作为细胞碳的唯一来源，并且将CO2固定成有机化合物是数量上最重要的生命过程。这种能力不仅存在于植物中，也存在于大多数主要的细菌中。已经建立了三种自养途径，即卡尔文循环、还原性柠檬酸循环和还原性乙酰辅酶A途径。该项目旨在研究细菌中新的CO2固定途径。第一个目标是阐明所提出的3-羟基丙酸循环，其功能为光养真细菌Chloroflexus aurantiacus中的自养途径。这种模式生物的基因组已经测序。第二个目标是研究嗜热泉古菌中类似但经过修改的循环。这组古细菌可能含有其他的自养途径，将进行研究。该项目有望为各种细菌的生理和代谢提供新的见解。此外，新酶和途径的发现将对生物化学和进化生物学产生影响。最后，可以设想一些应用。

Autotrophy is the use of carbon dioxide (CO2) as sole source of cell carbon, and autotrophic CO2-fixation into organic compounds is the quantitatively most important life process. This capability is found not only in plants but also in most major groups of bacteria. Three autotrophic pathways have been established, the Calvin cycle, the reductive citric acid cycle, and the reductive acetyl-CoA pathway. This project aims at studying new CO2-fixation pathways in bacteria. The first goal is the elucidation of the proposed 3-hydroxypropionate cycle which functions as autotrophic pathway in the phototrophic eubacterium Chloroflexus aurantiacus. The genome of this model organism has been sequenced. The second aim is the study of similar but modified cycle in thermophilic Crenarchaeota. This group of archaebacteria may harbor other autotrophic pathways which will be studied. This project is expected to provide new insights into the physiology and metabolism of various bacteria. Furthermore, the discovery of new enzymes and pathways will have an impact on biochemistry and evolutionary biology. Finally, some applications can be envisaged.