A Biotechnological Approach for Plakortin Production: New Perspectives for Bioactive Compounds from Marine Source

A variety of limiting factors currently affect the full exploitation of bioactive natural products from marine invertebrates, the most important being the supply problem. Large-scale total synthesis is usually prevented by the complex structure of most natural products, while a massive collection of the organisms producing compounds of industrial interest appears unrealistic. New perspectives were opened by the discovery that several (and probably a significant portion) of these bioactive compounds are produced by bacterial symbionts, but even so, production by fermentation is often impossible because very few symbiotic species can be cultured with the present techniques. We are currently exploring a biotechnological approach for the inexpensive and reproducible production of marine natural compounds. 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. 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 50,000 clone library which was PCR-screened in search of the PKS gene cluster 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 latest results of this project will be presented. 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 many other bioactive compounds from marine invertebrate.