Identification of BagI as a positive transcriptional regulator of bagremycin biosynthesis in engineered Streptomyces sp. Tü 4128

Bagremycin A and B, two novel antibiotics from Streptomyces sp. Tü 4128, show a moderate activity against fungi, Gram-positive bacteria and tumor cell and have potential application values in the fields of medicine and agriculture. In this study, we obtained a bagI deletion mutant by in-frame deletion. The assays of bagI-deletion and complementation strains revealed that it was essential to bagremycin biosynthesis. Secondly, the impact of bagI mutants on mycelial growth, sporulation and pigment yields was explored throughout secondary metabolism. SEM images displayed that bagI mutation delayed the mycelium growth and sporulation and reduced pigment yields. Moreover, the yields of bagremycin A and B increased 2.5-fold and 2.6-fold in bagI-overexpressed strain compared to WT. Thirdly, we investigated genes associated with bagremycin biosynthesis by real-time fluorescent quantitative PCR (qRT-PCR). Data showed that BagI played a role of transcriptional activator in the course of bagremycin biosynthesis. This provides us new insights into the regulatory network of bagremycin biosynthesis.