Antibacterial activity of endosymbiotic fungi isolated from marine sponges collected from Kotok Kecil Island, Seribu Islands, Jakarta

Abstract Endosymbiont fungi from marine sponges are a rich source of medicinally active compounds. Indonesia has a huge number of marine sponges. This research was conducted to determine the antibacterial potential of endosymbiont fungi isolated from marine sponges collected from Kotok Kecil Island, Seribu Islands. The screening was conducted with two methods, the modified GIBEX and disc diffusion. Species of marine sponges were isolated, namely Petrosia sp., Stylissa carteri, Cinachyrella australiensis, Callyspongia sp., Petrosia nigrians, and Stylissa massa, and obtained 9 isolates of endosymbiont fungi. The GIBEX test against Escherichia coli and Streptococcus mutans showed that ethyl acetate extract had strongest antibacterial activity. Disc diffusion test of ethyl acetate extract, five isolates had antibacterial activity against S. mutans and four against E. coli. The isolate that showed the strongest antibacterial activity was from Petrosia sp. Which has an inhibition zone of 8.4 mm against E. coli and 7.45 mm against S. mutans. The main active compounds from the isolate of Petrosia sp. are butylhydroxytoluene and phthalic acid di-(2-propylpentyl) esters. Based on this study, we concluded that the endosymbiont fungi of marine sponges are potential to be developed for further development as source of antibacterial agents.