Extensively modulating gene expression to achieve optimal flux is a critical step in metabolic engineering. Gene expression is usually modulated at the transcriptional level by controlling the strength of a promoter. However, this type of modulation is often hampered by its inability to fully sample the complete continuum of transcriptional control. In Escherichia coli, this limitation can be solved by constructing promoters with a wide range of strengths. In this study, a highly efficient method was developed to modulate a particular chromosomal gene of E. coli at a wide range of expression levels. This was achieved by combining highly efficient single-stranded oligonucleotide-mediated recombination and a stringent counter selection system kil. Using this strategy, a chromosomal library, with a range from 0.3% to 388% relative to the wild lac promoter, was easily obtained. The strength of our chromosomal promoter library was approximately 5-60 times wider in range than those of libraries reported before.

中文翻译：

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通过结合单链寡核苷酸介导的重组和kil反向选择系统来调节大肠杆菌中的染色体基因表达。

广泛调节基因表达以达到最佳通量是代谢工程中的关键步骤。通常通过控制启动子的强度在转录水平上调节基因表达。但是，这种类型的调制通常因无法完全采样转录控制的完整连续体而受到阻碍。在大肠杆菌中，可以通过构建具有广泛强度的启动子来解决这一局限性。在这项研究中，开发了一种高效的方法，可以在广泛的表达水平上调节大肠杆菌的特定染色体基因。这是通过结合高效的单链寡核苷酸介导的重组和严格的反选择系统而实现的。使用此策略，可建立一个范围为0的染色体库。相对于野生lac启动子，容易获得3％至388％。我们的染色体启动子文库的强度范围比以前报道的文库的强度宽约5-60倍。