Metabolic Flux Analysis of Escherichia coli creB and arcA Mutants Reveals Shared Control of Carbon Catabolism under Microaerobic Growth Conditions
Metabolic Flux Analysis of Escherichia coli creB and arcA Mutants Reveals Shared Control of Carbon Catabolism under Microaerobic Growth Conditions
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DOI：
10.1128/jb.00174-09
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发表时间：
2009-09-01
影响因子：
3.2
通讯作者：
Bennett, George N.
中科院分区：
文献类型：
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作者：
Nikel, Pablo I.;Zhu, Jiangfeng;Bennett, George N.
大肠杆菌具有多种复杂的传感机制，用于响应氧气和其他电子受体以及周围环境中碳源的可用性。其中，CreBC和ArcAB双组分信号转导系统分别负责调节碳源利用和响应氧气可用性的氧化还原控制。我们通过在野生型菌株、Delta creB 和 Delta arcA 单突变体以及 Delta creB Delta arcA 双突变体的恒化培养物中进行 C-13 标记实验，评估了 CreBC 和 ArcAB 在微需氧条件下调节大肠杆菌中心碳代谢的作用。在限制氧气供应的碳限制条件下，在 D = 0.1 h(-1) 时进行连续培养。尽管所有实验菌株主要通过 Embden-Meyerhof-Parnas 途径代谢葡萄糖，但突变菌株在氧化和非氧化戊糖磷酸途径中的通量均显着降低。在丙酮酸分支点也发现显着差异。丙酮酸-甲酸裂解酶和丙酮酸脱氢酶复合物都有助于丙酮酸合成乙酰辅酶 A，并且它们的活性似乎受到 ArcAB 和 CreBC 的调节。与野生型菌株及其 Delta arcA 衍生物相比，携带 creB 缺失的菌株显示出更高的葡萄糖生物量产量，这也与从结构单元到生物量的更高通量相关。乙醛酸旁路和乳酸脱氢酶主要在 Delta arcA 菌株中活跃。最后，观察到三羧酸循环反应在我们的实验条件下以相当循环的方式进行，突变株中的活性降低。
Escherichia coli has several elaborate sensing mechanisms for response to availability of oxygen and other electron acceptors, as well as the carbon source in the surrounding environment. Among them, the CreBC and ArcAB two-component signal transduction systems are responsible for regulation of carbon source utilization and redox control in response to oxygen availability, respectively. We assessed the role of CreBC and ArcAB in regulating the central carbon metabolism of E. coli under microaerobic conditions by means of C-13-labeling experiments in chemostat cultures of a wild-type strain, Delta creB and Delta arcA single mutants, and a Delta creB Delta arcA double mutant. Continuous cultures were conducted at D = 0.1 h(-1) under carbon-limited conditions with restricted oxygen supply. Although all experimental strains metabolized glucose mainly through the Embden-Meyerhof-Parnas pathway, mutant strains had significantly lower fluxes in both the oxidative and the nonoxidative pentose phosphate pathways. Significant differences were also found at the pyruvate branching point. Both pyruvate-formate lyase and the pyruvate dehydrogenase complex contributed to acetyl-coenzyme A synthesis from pyruvate, and their activity seemed to be modulated by both ArcAB and CreBC. Strains carrying the creB deletion showed a higher biomass yield on glucose compared to the wild-type strain and its Delta arcA derivative, which also correlated with higher fluxes from building blocks to biomass. Glyoxylate shunt and lactate dehydrogenase were active mainly in the Delta arcA strain. Finally, it was observed that the tricarboxylic acid cycle reactions operated in a rather cyclic fashion under our experimental conditions, with reduced activity in the mutant strains.