中文摘要：

【目的】洛蒙真菌素是在洛蒙德链霉菌（Streptomyces lomondensis）中生物合成的一种具有广谱抑菌活性的吩嗪类抗生素,但其合成机理仍不清晰。在洛蒙德链霉菌S015的洛蒙真菌素生物合成核心基因簇下游,有一甲基转移酶基因——lomo3,研究该基因对洛蒙真菌素生物合成的影响。【方法】对lomo3基因进行无痕敲除得到基因缺失突变株S015Δlomo3,再过表达重组质粒构建回补突变株S015Δlomo3：：lomo3,比较两株突变株与野生型S015的发酵产物的变化。【结果】发现基因缺失菌株S015Δlomo3不能合成洛蒙真菌素,而基因回补菌株S015Δlomo3：：lomo3则可恢复洛蒙真菌素的合成能力。【结论】甲基转移酶基因lomo3在洛蒙真菌素生物合成过程中起着重要的作用,但该基因的具体功能还有待深入研究。研究对于阐明洛蒙真菌素的生物合成途径具有一定的指导作用。

英文摘要：

[Objective] Lomofungin is a phenazine antibiotic with broad-spectrum anti-bacterial activity and is biosynthesized by Streptomyces lomondensis. In the lomofungin producing strain, S. lomondensis S015, a methyltransferase gene lomo3 at the downstream of the phenazine biosynthesis core gene cluster was studied. [Methods] We inactivated lomo3 by in-frame partial deletion and obtained strain S015Δlomo3. Complementary strain S015Δlomo3：：lomo3 was then constructed. To investigate the function of lomo3, we analyzed the metabolites in the fermentation broth of S015, S015Δlomo3 and S015Δlomo3：：lomo3. [Results] Inactivation of lomo3 in S. lomondensis S015 resulted in the absence of lomofungin production. The lomo3 complementary strain S015Δlomo3：：lomo3 regained the biosynthesis of lomofungin. [Conclusion] This methyltransferase gene lomo3 plays an important role in the biosynthesis of lomofungin. The information obtained in this study laid a theoretical foundation for the biosynthesis of lomofungin.