Streptomycetes are well-known producers of biologically active secondary metabolites. Various efforts have been made to increase productions of these metabolites, while few approaches could well coordinate the biosynthesis of secondary metabolites and other physiological events of their hosts. Here we develop a universal autoregulated strategy for fine-tuning the expression of secondary metabolites biosynthetic gene clusters (BGCs) in Streptomyces species. First, inducible promoters were used to control the expression of secondary metabolites BGCs. Then, the optimal induction condition was determined by response surface model in both dimensions of time and strength. Finally, native promoters with similar transcription profile to the inducible promoter under the optimal condition were identified based on time-course transcriptome analyses, and used to replace the inducible promoter following an elaborate replacement approach. The expression of actinorhodin (Act) and heterogeneous oxytetracycline (OTC) BGCs were optimized in Streptomyces coelicolor using this strategy. Compared to modulating the expression via constitutive promoters, our strategy could dramatically improve the titers of Act and OTC by 1.3- and 9.1-fold, respectively. The autoregulated fine-tuning strategy developed here opens a novel route for titer improvement of desired secondary metabolites in Streptomyces.

中文翻译：

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一种自动调节的精细调节策略，可利用链霉菌中的天然启动子改善次生代谢产物的滴定度

链霉菌是众所周知的具有生物活性的次级代谢产物的生产者。为了增加这些代谢产物的产量，人们进行了各种努力，而很少有方法可以很好地协调次生代谢产物的生物合成及其宿主的其他生理事件。在这里，我们开发了一种通用的自动调节策略，用于微调链霉菌中次级代谢产物生物合成基因簇（BGC）的表达。物种。首先，使用诱导型启动子来控制次生代谢产物BGC的表达。然后，通过响应面模型在时间和强度两个维度上确定最佳诱导条件。最后，基于时程转录组分析，鉴定了在最佳条件下具有与诱导型启动子相似的转录谱的天然启动子，并在精心设计的替代方法后用于替代诱导型启动子。使用此策略优化了天蓝色链霉菌中放线菌丝蛋白（Act）和异源土霉素（OTC）BGC的表达。相比调节的表达通过作为组成型启动子，我们的策略可以分别将Act和OTC的效价分别提高1.3倍和9.1倍。此处开发的自动调节微调策略为链霉菌中所需次级代谢产物的效价提高开辟了一条新途径。