Discovery and engineered overproduction of antimicrobial nucleoside antibiotic A201A from the deep-sea marine actinomycete Marinactinospora thermotolerans SCSIO 00652

Marinactinospora thermotolerans SCSIO 00652, originating from a deep-sea marine sediment of the South China Sea, was discovered to produce antimicrobial nucleoside antibiotic A201A. Whole-genome scanning and annotation strategies enabled us to localize the genes responsible for A201A biosynthesis and to experimentally identify the gene cluster; inactivation of mtdF , an oxidoreductase gene within the suspected gene cluster, abolished A201A production. Bioinformatics analysis revealed that a gene designated mtdA furthest upstream within the A201A biosynthetic gene cluster encodes a GntR family transcriptional regulator. To determine the role of MtdA in regulating A201A production, the mtdA gene was inactivated in frame and the resulting Δ mtdA mutant was fermented alongside the wild-type strain as a control. High-performance liquid chromatography (HPLC) analyses of fermentation extracts revealed that the Δ mtdA mutant produced A201A in a yield ∼25-fold superior to that of the wild-type strain, thereby demonstrating that MtdA is a negative transcriptional regulator governing A201A biosynthesis. By virtue of its high production capacity, the Δ mtdA mutant constitutes an ideal host for the efficient large-scale production of A201A. These results validate M. thermotolerans as an emerging source of antibacterial agents and highlight the efficiency of metabolic engineering for antibiotic titer improvement.