| Summary: | The one strain many compounds (OSMAC) strategy is an effective method for activating silent gene clusters by cultivating microorganisms under various conditions. The whole genome sequence of the marine-derived strain<i> Streptomyces globisporus</i> SCSIO LCY30 revealed that it contains 30 biosynthetic gene clusters (BGCs). By using the OSMAC strategy, three types of secondary metabolites were activated and identified, including three angucyclines, mayamycin A (<b>1</b>), mayamycin B (<b>2</b>), and rabolemycin (<b>3</b>); two streptophenazines (streptophenazin O (<b>4</b>) and M (<b>5</b>)); and a macrolide dimeric dinactin (<b>6</b>), respectively. The biosynthetic pathways of the secondary metabolites in these three families were proposed based on the gene function prediction and structural information. The bioactivity assays showed that angucycline compounds <b>1</b>–<b>3</b> exhibited potent antitumor activities against 11 human cancer cell lines and antibacterial activities against a series of Gram-positive bacteria. Mayamycin (<b>1</b>) selectively exhibited potent cytotoxicity activity against triple-negative breast cancer (TNBC) cell lines such as MDA-MB-231, MDA-MB-468, and Bt-549, with IC<sub>50</sub> values of 0.60–2.22 μM.
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