Antibacterial activity of the marine sponge Psammaplysilla purpurea: importance of its surface-associated bacteria

Among marine invertebrates, sponges are the most prolific phylum, with regard to presence of novel pharmacologically active compounds. Several marine sponges were collected from Gulf of Mannar, India and screened for their antibacterial activity against various pathogenic bacteria. The sponge Psammaplysilla purpurea which showed remarkable antibacterial activity was selected for the present study. Antifouling activity was checked against a set of fouling bacteria isolated from antifouling paint coated plates. Sponge microbial associations have long been documented, but relatively little is known about the nature of their interactions. Bacteria living on the surface of marine invertebrates have been found to produce chemicals that are having potential antibacterial and antifouling activities. To test this hypothesis about 102 bacterial isolates associated with the sponge were obtained using standard procedures. Among them three isolates were selected and further investigated not only for the ability and enhancement of antibiotic production against pathogenic Escherichia coli but also for the ability to inhibit the growth of fouling bacteria. The present findings show the importance of sponge surface-associated bacteria in producing new natural compounds.