Direct capture and expression of the didemnin anti-cancer agents from the marine bacterium Tistrella mobilis

The cyclic depsipeptide didemnin B was the first marine natural product to enter clinical trials as a chemotherapeutic agent. Although the compound and several analogs were originally isolated from tunicates, it was recently discovered that two species of free-living marine bacteria, Tistrella mobilis from the Red Sea and Tistrella bauzanesis from the Pacific Ocean, also produce the didemnins. To investigate the biosynthesis and unique post-synthetase activation mechanism of these compounds, the 75-kb biosynthetic gene cluster was directly captured from Tistrella mobilis KA081020-065 using transformation-associated recombination (TAR) in yeast. Attempts of heterologous expression in several Gram-negative proteobacterial expression hosts will provide a detailed mechanism of didemnin B biosynthesis, as well as an understanding of whether the gene cluster can be re-engineered to directly produce aplidine (dehydrodidemnin B), a drug with orphan designation in the EU.