Institute of Bio- and Geosciences, Biotechnology, Systemic Microbiology, Forschungszentrum Jülich GmbH, Jülich, Germany.
Biotechnol Bioeng. 2012 Aug;109(8):2070-81. doi: 10.1002/bit.24486. Epub 2012 Mar 22.
We here developed a series of Corynebacterium glutamicum strains with gradual decreased specific citrate synthase (CS) activity and quantified in a multifaceted approach the consequences of residual activity on the transcriptome, metabolome, and fluxome level as well as on L-lysine formation and growth. We achieved an intended gradual L-lysine yield increase and recognized and overcame further new limitations in the L-lysine biosynthesis pathway to result in a strain with the highest yield reported so far when assayed under comparable conditions. As a non-intended outcome, a detailed flux analysis revealed an almost constant flux through CS at 10% remaining CS activity, whereas the metabolome data revealed an increase in the oxaloacetate and acetyl-CoA concentrations. Hence reduced CS activity is apparently efficiently buffered by increased concentrations of CS substrates, implying a certain robustness of the central metabolism in response of the imposed gene expressions.
我们在这里开发了一系列具有逐渐降低的特异性柠檬酸合酶 (CS) 活性的谷氨酸棒杆菌菌株，并以多方面的方法定量研究了剩余活性对转录组、代谢组和通量组水平以及 L-赖氨酸形成和生长的影响。我们实现了预期的逐渐增加 L-赖氨酸产量，并在 L-赖氨酸生物合成途径中发现并克服了新的限制，从而在可比条件下获得了迄今为止报道的最高产量的菌株。作为一个非预期的结果，详细的通量分析表明，在 CS 活性残留 10%的情况下，CS 几乎保持恒定的通量，而代谢组数据显示草酰乙酸和乙酰辅酶 A 的浓度增加。因此，CS 活性的降低显然可以通过增加 CS 底物的浓度来有效地缓冲，这意味着在应对所施加的基因表达时，中心代谢具有一定的稳健性。
