二氧化碳固定是缓解温室效应的重要手段。罗氏真养菌(Ralstonia eutropha)通过化能自养方式固定二氧化碳，并在体内大量合成聚羟基丁酸酯（PHB）。该菌化能自养发酵过程以氢、二氧化碳和氧为底物，研究发现低氧能够诱导PHB 的胞内合成，然而其机制尚不清楚。本项目拟对自养罗氏真养菌固定二氧化碳合成PHB过程中，低氧促进PHB 合成的分子机制开展研究。首先，通过比较基因组学、蛋白组学等手段，阐明分别在低氧和高氧浓度下罗氏真养菌固定二氧化碳过程，基因转录和蛋白表达差异，并结合生物信息学分析，发现低氧诱导PHB合成关键基因及转录因子；其次，通过酵母单杂交和基因组编辑（敲除或过量表达）技术，以发现的转录因子为基础，对罗氏真养菌中耗氧能量代谢基因簇、PHB 合成基因簇、及其它发现的低氧诱导基因及转录因子结合位点进行验证，进而揭示低氧诱导PHB合成的分子机制。

Carbon dioxide fixation is an important way to remit the greenhouse effect. Ralstonia eutropha H16 has the ability of assimilating carbon dioxide to produce the degradable plastics - poly[R-(–)-3-hydroxybutyrate] (PHB). This strain uses the gas mixture of carbon dioxide, hydrogen and oxygen as substrate for PHB production through chemoautotrophic cultivation. It has been found that the low-oxygen condition can promote PHB accumulation. However, its mechanism is unclear. In this project, we are going to reveal the molecular mechanism of promoting PHB synthesis by low-oxygen condition for Ralstonia eutropha H16 during chemoautotrophic cultivation. Firstly, we will illuminate the differences of the gene transcription and protein expression between low-oxygen and high-oxygen carbon dioxide fixation processes by using the methods of comparative genomics and proteomics, and find out the hypoxia-inducible PHB synthetic genes and transcription factors by combining these differences of the gene transcription and protein expression with bioinformatics analysis of Ralstonia eutropha H16. Secondly, based on the detected transcription factors, we will verify the binding sites of the energy metabolism gene clusters, PHB synthesis gene cluster, and other found hypoxia-inducible genes and transcription factors, by using the yeast single hybridization and genome editing (knockout or overexpression) technologies. After such research, we will reveal the molecular mechanisms of hypoxic -inducible PHB synthesis.