Biotechnological Approaches for Plakortin: New Perspectives on the Study of Bioactive Compounds from Marine Source

A variety of limiting factors currently affect the full exploitation of bioactive marine natural products. Sponge symbiotic bacteria are believed to be the true producers of many of these compounds, but only a small portion of them can be cultured in the laboratory today. Moreover, large-scale total synthesis is usually prevented by the complex structure of most natural products, while a massive collection of marine organisms producing compounds of industrial interest appears unrealistic. We are currently exploring a biotechnological approach to solve the lack of a method for inexpensive and reproducible production of marine natural compounds under controlled conditions (the so-called supply problem) and to meet the demands of pre-clinical and clinical development. Our research is focused on the study of the biosynthetic pathway of plakortin (and related compounds), a polyketide peroxide with interesting antimalarial properties which is present in the marine sponge Plakortis simplex and is biosynthesized by a uncultivable bacterial symbiont of the sponge.1 We intend to identify, isolate and sequence the biosynthetic gene cluster for plakortin (presumably coding for a type-I polyketide synthase), and subsequently to express the pathway heterologously to produce plakortin by fermentation. Metagenomic DNA from Plakortis simplex was cloned to generate a 50000 clone library which was partially PCR-screened in search of the gene of PKS involved in the biosynthesis of plakortin. One positive clone was isolated and fully shotgun sequenced. The PKS gene is located at one end of the insert, so that only a small part of the PKS gene cluster is present in the insert (9 kbp). Following these encouraging results, we are currently searching for the remaining part of the cluster. The presentation will report the latest results of this project. The success of this research will demonstrate the feasibility of this strategy for the large-scale production of natural products, which could be applied to all new bioactive compounds from marine organisms.