Screening Antimicrobial Activity of Actinomycetes Isolated from Raja Ampat, West Papua, Indonesia

In the framework of exploitation of antimicrobial activity of Actinomycetes in Papua, one hundred isolates ofActinomycetes isolated from soil and leaf litter samples from various ecosystems in Batanta and Salawati Island, RajaAmpat, West Papua were screened. We obtained 200 crude extracts from 100 isolates based on two extraction phases.Nonpolar metabolites were extracted by ethyl acetate : methanol (4:1) solvent while the polar metabolites wereconcentrated using a freeze-drying method. Based on the agar dilution method, a total of 43 from 200(21.5%) crudeextracts have antimicrobial activity against bacteria and yeasts (Escherichia coli NBRC 14237, Bacillus subtilis NBRC3134, Staphylococcus aureus NBRC 13276, Micrococcus luteus NBRC 1367, Candida albicans NBRC 1594 andSaccharomyces cerevisiae NBRC 10217). Some crude extracts showed anti-Gram negative (1.5%), anti-Gram positive(17%) and antifungal (17%) activities. Crude metabolites which were extracted using ethyl acetate : methanol weremore effective on antimicrobial activity (35%) compared with water extraction (17%). Five most potential isolates (BL-13-5, BL-06-5, BL-14-2, BL-22-3, and Sl-36-1) were identified based on 16S rRNA gene sequence data. Sequencesimilarity search by BLAST program revealed that they show sequence similarities to Streptomyces kanamyceticus(92%), Streptomyces verne (92%), Streptomyces narbonensis (92%), Streptomyces malachitofuscus (98%), andStreptomyces hygroscopicus (96%), respectively.