AimsSessile marine invertebrates engage in a diverse array of beneficial interactions with bacterial symbionts. One feature of some of these relationships is the presence of bioactive natural products that can defend the holobiont from predation, competition or disease. In this study, we investigated the antimicrobial activity and microbial community of a common temperate sponge from coastal North Carolina. Methods and ResultsThe sponge was identified as a member of the genus Haliclona, a prolific source of bioactive natural products, based on its 18S rRNA gene sequence. The crude chemical extract and methanol partition had broad activity against the assayed Gram-negative and Gram-positive pathogenic bacteria. Further fractionation resulted in two groups of compounds with differing antimicrobial activity, primarily against Gram-positive test organisms. There was, however, notable activity against the Gram-negative marine pathogen, Vibrio parahaemolyticus. Microbial community analysis of the sponge and surrounding sea water via denaturing gradient gel electrophoresis (DGGE) indicates that it harbours a distinct group of bacterial associates. ConclusionsThe common temperate sponge, Haliclona sp., is a source of multiple antimicrobial compounds and has some consistent microbial community members that may play a role in secondary metabolite production. Significance and Impact of the StudyThese data suggest that common temperate sponges can be a source of bioactive chemical and microbial diversity. Further studies may reveal the importance of the microbial associates to the sponge and natural product biosynthesis.