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Modelling and Analysis of Central Metabolism Operating Regulatory Interactions in Salt Stress Conditions in a L-Carnitine Overproducing E. coli Strain

机译:在过量生产L-肉碱的大肠杆菌菌株中,在盐胁迫条件下的中央代谢操作调控相互作用的建模和分析

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摘要

Based on experimental data from E. coli cultures, we have devised a mathematical model in the GMA-power law formalism that describes the central and L-carnitine metabolism in and between two steady states, non-osmotic and hyperosmotic (0.3 M NaCl). A key feature of this model is the introduction of type of kinetic order, the osmotic stress kinetic orders (gOSn), derived from the power law general formalism, which represent the effect of osmotic stress in each metabolic process of the model.By considering the values of the gOSn linked to each metabolic process we found that osmotic stress has a positive and determinant influence on the increase in flux in energetic metabolism (glycolysis); L-carnitine biosynthesis production; the transformation/excretion of Acetyl-CoA into acetate and ethanol; the input flux of peptone into the cell; the anabolic use of pyruvate and biomass decomposition. In contrast, we found that although the osmotic stress has an inhibitory effect on the transformation flux from the glycolytic end products (pyruvate) to Acetyl-CoA, this inhibition is counteracted by other effects (the increase in pyruvate concentration) to the extent that the whole flux increases. In the same vein, the down regulation exerted by osmotic stress on fumarate uptake and its oxidation and the production and export of lactate and pyruvate are reversed by other factors up to the point that the first increased and the second remained unchanged.The model analysis shows that in osmotic conditions the energy and fermentation pathways undergo substantial rearrangement. This is illustrated by the observation that the increase in the fermentation fluxes is not connected with fluxes towards the tricaboxylic acid intermediates and the synthesis of biomass. The osmotic stress associated with these fluxes reflects these changes. All these observations support that the responses to salt stress observed in E. coli might be conserved in halophiles.Flux evolution during osmotic adaptations showed a hyperbolic (increasing or decreasing) pattern except in the case of peptone and fumarate uptake by the cell, which initially decreased. Finally, the model also throws light on the role of L-carnitine as osmoprotectant.
机译:基于来自大肠杆菌培养物的实验数据,我们在GMA幂律形式主义中设计了一个数学模型,该模型描述了非渗透性和高渗透性(0.3 M NaCl)两种稳态之间及其之间的中枢和左旋肉碱代谢。该模型的关键特征是引入了动力阶次类型,即渗透力动力学阶次(gOSn),它是从幂律一般形式主义派生而来的,代表了渗透压在模型每个代谢过程中的作用。与每个代谢过程相关的gOSn值,我们发现渗透压对能量代谢(糖酵解)通量的增加具有正向和决定性的影响;左旋肉碱的生物合成生产;乙酰辅酶A转化/分泌为乙酸盐和乙醇;蛋白of进入细胞的输入通量;丙酮酸的合成代谢用途和生物质分解。相反,我们发现尽管渗透压对从糖酵解终产物(丙酮酸)到乙酰辅酶A的转化通量具有抑制作用,但这种抑制作用在一定程度上抵消了其他影响(丙酮酸浓度的增加)。整个通量增加。同样,渗透压对富马酸酯摄取及其氧化的下调以及乳酸和丙酮酸的生产和出口被其他因素逆转,直至第一个增加而第二个保持不变。模型分析表明在渗透条件下,能量和发酵途径会发生重大的重排。通过观察可知,发酵通量的增加与通向三丁酸中间体和生物质合成的通量无关。与这些通量相关的渗透应力反映了这些变化。所有这些观察结果都证明在嗜盐菌中可能保留了对大肠杆菌中盐胁迫的反应。渗透适应过程中的通量演变显示出双曲线(增加或减少)模式,除了蛋白ept和富马酸盐被细胞吸收的情况(最初是减少。最后,该模型还阐明了左旋肉碱作为渗透保护剂的作用。

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