Table_1.XLSX

The ability of bacteria to produce polyhydroxyalkanoates such as poly(3-hydroxybutyrate) (PHB) enables provision of a carbon storage molecule that can be mobilized under demanding physiological conditions. However, the precise function of PHB in cellular metabolism has not been clearly defined. In order to determine the impact of PHB production on global physiology, we have characterized the properties of a ΔphaC1 mutant strain of the diazotrophic bacterium Herbaspirillum seropedicae. The absence of PHB in the mutant strain not only perturbs redox balance and increases oxidative stress, but also influences the activity of the redox-sensing Fnr transcription regulators, resulting in significant changes in expression of the cytochrome c-branch of the electron transport chain. The synthesis of PHB is itself dependent on the Fnr1 and Fnr3 proteins resulting in a cyclic dependency that couples synthesis of PHB with redox regulation. Transcriptional profiling of the ΔphaC1 mutant reveals that the loss of PHB synthesis affects the expression of many genes, including approximately 30% of the Fnr regulon.细菌合成聚羟基脂肪酸酯（polyhydroxyalkanoates）如聚(3-羟基丁酸酯)（PHB）的能力，使其能够产生一种可在严苛生理条件下被动员的碳储存分子。然而，PHB在细胞代谢中的精确功能尚未得到明确界定。为探明PHB合成对全局生理的影响，我们对固氮细菌（diazotrophic bacterium）斯氏草螺菌（Herbaspirillum seropedicae）的ΔphaC1突变菌株的特性进行了表征。该突变菌株无法合成PHB，不仅扰乱了氧化还原平衡、加剧了氧化应激，还影响了感应氧化还原的Fnr转录调控因子（redox-sensing Fnr transcription regulators）的活性，进而导致电子传递链的细胞色素c分支的表达发生显著变化。PHB的合成本身依赖Fnr1与Fnr3蛋白，由此形成一种将PHB合成与氧化还原调控相偶联的循环依赖关系。对ΔphaC1突变菌株的转录组分析（transcriptional profiling）显示，PHB合成的缺失会影响大量基因的表达，其中约30%的基因属于Fnr调控子（regulon）。