Identification and Antimicrobial Activities of Streptomyces Strains Isolated from Soils

Abstract

Thirty five strains of Streptomyces from 24 soil samples collected in Krabi, Chaiyaphoom, Chanthaburi, Chonburi, Lampang, Kanchanaburi, Nongkhai, Ratchaburi, Chachoengsao, and Srakaew provinces in Thailand were screened for antimicrobial activities. Thirty strains exhibited antibacterial activity against Bacillus subtilis ATCC 6633, 15 strains inhibited Staphylococcus aureus ATCC 25933, 3 strains inhibited Escherichia coli ATCC 25922 and only a strain CB5-3 showed antifungal activity against C. albicans ATCC 10231. The potent strain CB5-3, was selected for further antimicrobial activity tests and fermentation. On the basis of the morphological, cultural, physiological and biochemical characteristics including the 16S rDNA sequence similarity (99.9%) of strain CB5-3 was closely related to Streptomyces hygroscopicus NBRC 13868^T, therefore, it was identified as Streptomyces hygroscopicus. In addition, the antibiotic fermentation of this CB5-3 strain was carried out in peptone-yeast extract (PY) medium at 28 °C for 14 days. The isobutanol extract of fermentation broth was tested by bioautographic method and found that the active spot was shown at R_f 0.7 value. This isolated extract was shown to be active against Candida albicans ATCC 10231.