Antimicrobial activity of tropical and subtropical sponges

Extracts of 19 of 24 species of sponge collected from Queensland, Australia, inhibited the growth of test microorganisms in in-vitro assays. A similar result has been obtained by earlier workers for extracts of species of sponge obtained from temperate waters. Some of the extracts, including extracts of Thorecta vasiforis, Arenochalina mirabilis and Acanthella kleutha , showed activity against bacterial strains that was comparable with that exhibited by penicillin G and streptomycin against these strains. Gram-positive bacteria were especially sensitive to many extracts. Little activity was exhibited by any extract against four species of fungi tested. Some of the extracts were markedly toxic to one or more of the test organisms (a fish, a crustacean and a hydroid) used, but no clear pattern linking toxicity to these organisms with antimicrobial properties of the extracts emerged. In general, there was a negative correlation between antimicrobial activity and surface-fouling, raising the possibility of using freedom from surface-fouling as an indicator of antimicrobial activity. There are indications that antimicrobial activity may be widespread in the order Dictyoceratida, in the order Verongida and in the order Axinellida, but sporadic in other orders of Porifera.