BACKGROUND Heterologous expression of secondary metabolite gene clusters is used to achieve increased production of desired compounds, activate cryptic gene clusters, manipulate clusters from genetically unamenable strains, obtain natural products from uncultivable species, create new unnatural pathways, etc. Several Streptomyces species are genetically engineered for use as hosts for heterologous expression of gene clusters. S. lividans TK24 is one of the most studied and genetically tractable actinobacteria, which remain untapped. It was therefore important to generate S. lividans chassis strains with clean metabolic backgrounds. RESULTS In this study, we generated a set of S. lividans chassis strains by deleting endogenous gene clusters and introducing additional φC31 attB loci for site-specific integration of foreign DNA. In addition to the simplified metabolic background, the engineered S. lividans strains had better growth characteristics than the parental strain in liquid production medium. The utility of the developed strains was validated by expressing four secondary metabolite gene clusters responsible for the production of different classes of natural products. Engineered strains were found to be superior to the parental strain in production of heterologous natural products. Furthermore, S. lividans-based strains were better producers of amino acid-based natural products than other tested common hosts. Expression of a Streptomyces albus subsp. chlorinus NRRL B-24108 genomic library in the modified S. lividans ΔYA9 and S. albus Del14 strains resulted in the production of 7 potentially new compounds, only one of which was produced in both strains. CONCLUSION The constructed S. lividans-based strains are a great complement to the panel of heterologous hosts for actinobacterial secondary metabolite gene expression. The expansion of the number of such engineered strains will contribute to an increased success rate in isolation of new natural products originating from the expression of genomic and metagenomic libraries, thus raising the chance to obtain novel biologically active compounds.

中文翻译：

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Lividans链霉菌工程化用于次级代谢产物基因簇的异源表达。

背景技术次级代谢产物基因簇的异源表达用于实现所需化合物的增加产量，激活隐性基因簇，从遗传难以适应的菌株中操纵簇，从不可耕种物种获得天然产物，创造新的非自然途径等。用作宿主基因簇的异源表达。lividans TK24是研究最多，遗传上最易处理的放线菌之一，至今尚未开发。因此，重要的是要产生具有干净代谢背景的淡紫色链霉菌底盘菌株。结果在这项研究中，我们通过删除内源基因簇并引入额外的φC31attB基因座来定点整合外源DNA，从而产生了一套S. lividans底盘菌株。除了简化的代谢背景外，在液体生产培养基中，改造的S. lividans菌株比亲本菌株具有更好的生长特性。通过表达负责产生不同种类天然产物的四个次级代谢产物基因簇，验证了所开发菌株的效用。发现工程菌株在异源天然产物的生产中优于亲本菌株。此外，基于S. lividans的菌株比其他经过测试的常见宿主更能生产基于氨基酸的天然产物。链霉菌亚种的表达。改良的S. lividansΔYA9和S. albus Del14菌株中的绿藻NRRL B-24108基因组文库导致产生了7种潜在的新化合物，两种菌株中仅产生一种。结论构建的基于Lividans的菌株是放线菌次级代谢产物基因表达的异源宿主的重要补充。此类工程菌株数量的增加将有助于提高成功的成功率，以分离源自基因组和宏基因组文库表达的新天然产物，从而增加获得新型生物活性化合物的机会。