Screening of antimicrobial and toxicity activity of endophytic bacteria associated with Curcuma Zedoaria

Indonesian has been used Curcuma zedoaria as a herbal in cancer treatment. The bioactive compounds contained in the medicinal plants are products by the plant itself or by endophytes living inside the plant. Zebrafish has been used for the study in several areas of cancer research, including angiogenesis, metastasis, antitumor drug screening, and toxicity. This study was to investigate the antimicrobial and toxicity activity of secondary metabolite from endophytic bacteria isolated from C. zedoaria. Endophytic isolates were screened for antimicrobial activities against six microbial pathogens Bacillus subtilis, Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Candida albicans, and Sacharomyces cerevisiae. Four of endophytic bacteria showed antimicrobial activity were tested in toxic compound producing through Fish Embryo Toxicity (FET) test using zebrafish. The results indicated that from 73 selected isolates, 16 isolates (21.92%) showed antimicrobial activities against at least one of the test organisms. Four of endophytic bacteria that showed high antimicrobial activities, were identified as Citrobacter freundii, Bacillus subtilis, Pseudomonas otitidis, and Burkholderia cenocepacia. FET test of ethyl acetate extracts from the four those selected isolates revealed that they had LC₅₀ values 63.5; 24.7; 13.4; and 12.6 ppm, respectively. These result showed that the highest toxicity was obtained from B. cenocepacia extract.