Identification of the antifungal peptide-containing symbiont of the marinesponge Theonella swinhoei as a novel delta-proteobacterium, "Candidatus Entotheonella palauensis"

The Pulauan sponge Theonella swinhoei (class Demospongiae, order Lithistida , family Theunllidae) harbors filamentous bacterial symbionts that contain theopalauamide, an antifungal, bicyclic glycopeptide. In this study, the fi lamentous symbionts were shown to be novel bacteria belonging to the delta- subdivision of proteo-bacteria. The 16S rRNA gene sequence was determined u sing a combination of denaturing gradient-gel electrophoresis (DGGE) and sp ecific polymerase chain-reaction (PCR) primers, and its source was confirme d by in situ hybridization. In a series of culture experiments, the filamen tous bacteria were propagated in a mixed culture on agar plates, Related 16 S rRNA gene sequences were isolated from related sponges with slightly diff erent chemistry. The taxonomic status "Candidatus Entotheonella palauensis" is proposed for the theopalauamide-containing filamentous bacteria from T. swinhoei.