The fast-growing capability of Escherichia coli strains used to produce industrially relevant metabolites relies on their capability to transport efficiently glucose or potential industrial feedstocks such as sucrose or xylose as carbon sources. E. coli imports extracellular glucose into the periplasmic space across the outer membrane porins: OmpC, OmpF, and LamB. As the internal membrane is an impermeable barrier for sugars, the cell employs several primary and secondary active transport systems, and the phosphoenolpyruvate (PEP)-sugar phosphotransferase (PTS) system for glucose transport. PTS:glucose is the preferred system by E. coli to transport and phosphorylate the periplasmic glucose; nevertheless, PTS imposes a strict metabolic control mechanism on the preferential consumption of glucose over other carbon sources in sugar mixtures such as glucose and xylose resulting from the hydrolysis of lignocellulosic biomass, by the carbon catabolite repression. In this contribution, we summarize the major sugar transport systems for glucose and disaccharide transport, the exhibited substrate plasticity, and their impact on the growth of E. coli, highlighting the relevance of PTS in the control of the expression of genes for the transport and catabolism of other sugars as xylose. We discuss the strategies developed by evolved mutants of E. coli during adaptive laboratory evolution experiments to overcome the nutritional stress condition imposed by inactivation of PTS as a strategy for the selection of fast-growing derivatives in glucose, xylose, or mixtures of glucose:xylose. This approach results in the recruitment of other primary and secondary active transporters, demonstrating relevant sugar plasticity in derivative-evolved mutants. Elucidation of the molecular and biochemical basis of sugar-transport substrate plasticity represents a consistent approach for sugar-transport system engineering for the design of efficient E. coli derivative strains with improved substrate assimilation for biotechnological purposes.

中文翻译：

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新型糖突变体对糖的运输能力及其对生长的影响的新见解。

用于生产与工业相关的代谢产物的大肠杆菌菌株快速增长的能力取决于其有效运输葡萄糖或潜在的工业原料（如蔗糖或木糖）作为碳源的能力。大肠杆菌通过外膜孔蛋白（OmpC，OmpF和LamB）将胞外葡萄糖导入周质空间。由于内膜是糖的不可渗透的屏障，因此该细胞采用了几种主要和次要的主动转运系统，而磷酸烯醇丙酮酸（PEP）-糖磷酸转移酶（PTS）系统则用于葡萄糖转运。PTS：葡萄糖是大肠埃希氏菌传输和磷酸化周质葡萄糖的首选系统；但是，PTS规定了严格的代谢控制机制，即通过碳分解代谢物抑制，优先消耗糖类混合物中的其他碳源（例如葡萄糖和木糖）比其他碳源优先消耗葡萄糖，这是木质纤维素生物质水解产生的。在这项贡献中，我们总结了用于葡萄糖和二糖运输的主要糖运输系统，显示的底物可塑性及其对大肠杆菌生长的影响，强调了PTS在控制运输和运输基因表达方面的相关性。其他糖类分解代谢为木糖。我们讨论了大肠杆菌进化突变体在适应性实验室进化实验过程中开发的策略，以克服由于PTS失活而造成的营养应激状况，以此作为选择葡萄糖，木糖，或葡萄糖：木糖的混合物。这种方法导致募集其他主要和次要的活性转运蛋白，表明衍生物进化的突变体中相关的糖可塑性。糖运输底物可塑性的分子和生化基础的阐明代表了糖运输系统工程的一致方法，用于设计有效的大肠杆菌衍生物菌株，并为生物技术目的改进了底物的同化性。