Antibacterial antibiotics from Micromonospora species isolated from soil

Abstract

A total of 33 strains of dark hue, moist colonies were isolated from 22 marine and terrestrial soils samples collected from different provinces in Thailand. The results of primary screening of antimicrobial activities of them indicated that they could inhibit gram-positive bacteria Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, and gram-negative bacteria Escherichia coli ATCC 25922. Based on morphological, cultural, physiological, and biochemical characteristics studies, they were identified as Micromonospora species. The potent strains, JSM 5-1, JSM 1-3, and A-25 were used for antibiotics production in diverse liquid media at different pHs and temperatures. It was found that those cultivated in Glucose Soybean Medium, pH 7.0 at 28 ํC, showed high antibacterial activities. The ethyl acetate extract of the fermentation broth showed a wide range of antibacterial activities. Through the use of several chromatographic technique an isoflavanone was separated from this extract and identified as genistein. The structurc of this compound was determined by comparison of its MS and NMR properties with previously reported data.