Bagremycin B

New bagremycins C-E (3-5) and bagrelactone A (6), together with known bagremycins A (1) and B (2), 4-hydroxystyrene (7), and 4-hydroxystyrene 4-O-α-d-galactopyranoside (8), were isolated from a mangrove-derived actinomycete, Streptomyces sp. Q22. Structures of these new compounds were elucidated based on their NMR and HRESIMS spectroscopic data as well as chemical degradation. Bagremycin C (3) is a unique analogue with an N-acetyl-(S)-cysteine moiety, while bagrelactone A (6) represents the first example of this type of bagremycin-derived macrolide. Bagremycin C (3) was active against four glioma cell lines, with IC50 values in the range from 2.2 to 6.4 μM, induced apoptosis in human glioma U87MG cells in a dose- and time-dependent manner, and arrested the U87MG cell cycle at the G0/G1 phase.

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.

Bagremycin A and bagremycin B isolated from Streptomyces sp. Tü 4128 have activities against Gram-positive bacteria, fungi and also have a weak antitumor activity, which make them have great potential for development of novel antibiotics. Here, we report a draft genome 8,424,112 bp in length of S. sp. Tü 4128 by Illumina Hiseq2000, and identify the bagremycins biosynthetic gene cluster (BGC) by bioinformatics analysis. The putative bagremycins BGC includes 16 open reading frames (ORFs) with the functions of biosynthesis, resistance and regulation. Disruptions of relative genes and HPLC analysis of bagremycins production demonstrated that not all the genes within the BGC are responsible for the biosynthesis of bagremycins. In addition, the biosynthetic pathways of bagremycins are proposed for deeper inquiries into their intriguing biosynthetic mechanism.