Green macroalgae Caulerpa racemosa from the waters of Lemukutan Island was isolated to obtain its endophyte fungi. Endophyte fungi were explored to determine their potential as antibacterial. Isolation of endophyte fungi was carried out by dilution method using PDA media. Endophyte fungi with different morphology were obtained as many as 4 isolates, named CRF1, CRF2, CRF3 and CRF4. Antibacterial activity testing was carried out by agar diffusion method. Endophyte fungi isolate CRF3 showed the best activity against Escherichia coli bacteria while CRF2 isolate showed the best activity against Staphylococcus aureus with inhibition zone diameters of 15.83 mm and 11.99 mm, respectively. Keywords:Endophyte Fungi, Caulerpa racemosa, Antibacterial, Lemukutan

Green macroalgae Caulerpa racemosa from the waters of Lemukutan Island was isolated to obtain its endophyte fungi. Endophyte fungi were explored to determine their potential as antibacterial. Isolation of endophyte fungi was carried out by dilution method using PDA media. Endophyte fungi with different morphology were obtained as many as 4 isolates, named CRF1, CRF2, CRF3 and CRF4. Antibacterial activity testing was carried out by agar diffusion method. Endophyte fungi isolate CRF3 showed the best activity against Escherichia coli bacteria while CRF2 isolate showed the best activity against Staphylococcus aureus with inhibition zone diameters of 15.83 mm and 11.99 mm, respectively. Keywords:Endophyte Fungi, Caulerpa racemosa, Antibacterial, Lemukutan

Symbiotic microorganisms usually have the same secondary metabolite activity as their host. The aims of this study were determine the biodiversity of symbiotic microorganisms from Caulerpa racemosa grown in Lemukutan Island, Indonesia and evaluate their antibacterial activity. Thirty eight bacterial and eighteen fungal were isolated. All isolates showed antibacterial activity against Escherichia coli and Staphylococcus aureus. All fungal isolates were identified from spore morphology using a microscope and, the best bacterial isolates with highest antibacterial activity (IB21 and IB47) were identified using biochemical tests, such as gram staining, citrate test, MR-VP test, carbohydrate fermentation test, fermentative oxidation test, oxidation test, catalase test, indole test, motility test, urease test and hydrogen production test (H2S). The genera of isolated fungi were identified as genus Trichocladium, Aspergillus, Chaetomium, Coprinus, Cladorrhinum, Hymeochaete, Rhizopus, Tremella, Zygorhynchus, Mucor, and Bjerkandera. Meanwhile the best bacteria IB21 and IB47 were putatively identified as member of genus Corynebacterium and Neissiria, respectively.