A BROMINATED SECONDARY METABOLITE SYNTHESIZED BY THE CYANOBACTERIAL SYMBIONT OF A MARINE SPONGE AND ACCUMULATION OF THE CRYSTALLINE METABOLITE IN THE SPONGE TISSUE

The dictyoceratid marine sponge Dysidea herbacea (Keller, 1889) is com mon in shallow waters of the tropical Pacific Ocean. Polybrominated bi phenyl ethers such as 2-(2',4'-dibromophenyl)-4,6-dibromopheno (1) are characteristic secondary metabolites of some specimens of this sponge and may represent as much as 12% of the dry weight. We have found 1 t o be deposited as conspicuous crystals throughout the sponge tissue. T he dominant prokaryotic endosymbiont in the mesohyl of the sponge is a filamentous cyanobacterium (Oscillatoria spongeliae), although a vacu ole-containing, heterotrophic bacterium is also present. The cyanobact eria were separated from the sponge cells and heterotrophic bacteria b y flow cytometry. Coupled gas chromatography-mass spectrometry and pro ton nuclear magnetic-resonance spectroscopy revealed that the major br ominated Compound 1 isolated from the intact symbiotic association is found in the cyanobacteria and not in the sponge cells or heterotrophi c bacteria. This suggests that the production of the compound is due t o the cyanobacterium, and not to the sponge or symbiotic heterotrophic bacteria, as had been suggested earlier.