Bacterial symbionts of a marine invertebrate as sources of anticancer compounds

Marine invertebrates are host organisms for various symbiotic microorganisms and contain specific compounds that are of interest for bioactive products. In some cases these bioactive compounds may be produced by the invertebrate-associated microbes rather than by the invertebrate from which the compounds are derived. The marine invertebrate Elysia rufescens, a Hawaiian herbivorous marine mollusk, is host to a very diverse microbial community based on molecular and culture based analyses. A cyclic depsipeptide called Kahalalide F (KF), a leading antitumor compound is produced by two specific Vibrio species found in this diverse microbial assemblage. KF has demonstrated activity against liver cancer and is in phase II clinical trials for lung cancer and melanoma. The aim of this study is to further characterize these Vibrio sp. Fluorescence in situ hybridization is being used to detect and localize the KF producing Vibrio sp. within the mollusk. Based on growth curves, the Vibrios have begun producing KF only after many days in stationary phase. This work contributes toward developing methods for sustainable and optimized production of this bioactive compound through the effective characterization of the Vibrio sp. Our work also contributes to understanding of the roles of the Vibrios and production of KF in the overall ecology of the microbial community associated with E. rufescens.