Indentifiation and antimicrobial activity of actinomycetes strains isolated from marine samples in the coastal area of Thanh Hoa – Quang Binh – Quang Tri

Abstract

In this study, 46 strains of actinomycetes were isolated from 40 samples including: sediments, sponges, soft corals, echinoderms and starfish collected from three coastal areas of Vietnam: Thanh Hoa - Quang Binh – Quang Tri. The strains were fermented in A+ medium and fermentation broths were extracted 5 times with ethyl acetate then the extracts were evaporated under reduced pressure to yield crude extracts. Quantitative assay was used to determine MIC (Minimum inhibitory concentration) of extract against 7 reference strains. From the results of screening, five strains of actinomycetes exhibited the highest biological activity were chosen (Code: G212, G222, G233, G227 and G241). In particular, strains G222, G233, G227 and G241 were resistant 6/7 strains of microorganisms test, with MIC values from 64 µg/ml to 256 µg/ml; Moreover. All of the five strains were highly resistant to yeast Candida albicans ATCC10231. These strains were then subjected to morphological and phylogenetic investigations based on 16S rDNA gene sequences. The results showed that strains G212, G222 and G227 belonged to the genus Streptomyces; strains G233 and G24l were identified as a member of the genus Micromonospora.