Characterisation and antimicrobial activity of epibiotic bacteria from Petrosia ficiformis (Porifera, Demospongiae)

Numerous natural products from marine invertebrates show striking structural similarities to known metabolites of microbial origin, suggesting that microorganisms (bacteria, microalgae) are at least involved in their biosynthesis or are in fact the true sources of these respective metabolites. The viable epibiotic microbial community of the marine sponge Petrosia ficiformis was screened and characterised using classical and molecular techniques. Fifty-seven aerobic heterotrophic bacterial strains were isolated and presumptively identified by their phenotypic characters. Random Amplified Polymorphic DNA (RAPD) analysis of the non-fermentative Gram-negative strains and Corynebacteria was performed. Cluster analysis of RAPD data showed genetic relatedness among sponge isolates. Antimicrobial activity was found in several isolates, two of which were identified as Rhodococcus sp. and Pseudomonas sp. by partial 16S rRNA gene sequencing. The recovery of strains with antimicrobial activity suggests that marine sponges represent an ecological niche which harbours a largely uncharacterised microbial diversity and a yet unexploited potential in the search for new secondary metabolites. (C) 2004 Elsevier B.V. All rights reserved.