Characterization of cues from natural multi-species biofilms that induce larval attachment of the polychaete Hydroides elegans

Multi-species natural microbial biofilms have been identified as sources of cues to induce larval attachment of a broad range of sessile marine invertebrates. However, the chemical identities of the cues originating from these films have not been fully characterized. In this study, we isolated and characterized 2 compounds from natural biofilms that induced the larval attachment of the polychaete Hydroides elegans. Biofilms were developed on Petri dishes in seawater in the field for 6 d, collected from the Petri dishes using cotton buds, and extracted using a combination of polar and non-polar solvents. The non-polar fraction was inductive to larval attachment and was thus further fractionated using HPLC. Bioassay-guided fractionation was used to locate the active compounds that were then structurally characterized by using nuclear magnetic resonance (NMR) spectroscopy. Two inductive compounds were identified, a hydrocarbon (6,9-heptadecadiene) and a fatty acid (12-octadecenoic acid), which are the first chemical cues inductive to larval attachment of marine invertebrates isolated from natural biofilms.