Identification and antimicrobial activities of actinomycetes from soils in Samed Island, and geldanamycin from strain PC4 - 3 (original) (raw)

In the course of identification and screening for antimicrobial activities of 100 actinomycete isolates from 35 soil and sand samples collected from the shore of Samed Island, Rayong province, 79 isolates were identified as Streptomyces, 20 were Micromonospora, and one was Nocardia based on their morphological, cultural, physiological and biochemical characteristics. On primary screening for antimicrobial activities, 54 isolates of Streptomyces, 14 of Micromonospora, and one of Nocardia showed the activities against Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, and Candida albicans ATCC 10231, while the activities against Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 could be observed in few isolates. On secondary screening of 30 isolates, the strain PC4 -3 with good antimicrobial activity was selected for secondary metabolite fermentation. This strain contained LL -diaminopemelic acid in cell wall and was similar to Streptomyces sporoclivatus LMG 20312 T with 99.1% 16S rDNA sequence similarity. In addition, the representative strains of genera, MS7 -3 and SC36 -1 were closed to M. matsumotoense JCM 9104 T and Nocardia araoensis DSM 44729 T based on 98.6% and 99.3% of 16S rDNA sequence similarity, respectively. The ethyl acetate extract from fermentation broth of PC4 -3 showed antimicrobial activities against S. aureus ATCC 25923, B. subtilis ATCC 6633 and C. albicans ATCC 10231. Antimicrobial assay -guided fractionation of the ethyl acetate extract yielded 2 known ansamycins, including geldanamycin and 17 -O -demethylgeldanamycin. The chemical structures of the isolated compounds were elucidated through extensive analyses of UV, IR, MS and NMR spectroscopic data and comparison with the literatures. Geldanamycin exhibited antimicrobial activity against S. aureus ATCC 25923 and C. albicans ATCC 10231.