Chiang Mai Journal of Science

Actinomycetes provide various kinds of secondary metabolites, including antibiotics and other therapeutic compounds. This study examines actinomycetes isolated from mangrove soil samples from eastern Thailand, Chonburi and Chantaburi provinces. From a total of 44 different actinomycete colonies, 35 isolates showed antimicrobial activity against one or more test organisms. In addition, 12 from 35 isolates exhibited potent antimicrobial activity against test microbes with a broad spectrum of activity. Fermentation time course studies of these 12 isolates, three strains (LC1, TCH4 and SCH2) revealed a potent antimicrobial activity in comparison to others. Thus they were chosen for further cell-based study to explore the cytotoxic, morphological, physiological, biochemical and molecular characteristics. The cytotoxic assay showed the possibility of these three strains for anticancer activity with an IC50 lower than 1 %v/v. The nucleotide sequences of the 16S rDNA gene of the three strains matched with that of Streptomyces species in the morphological, physiological and biochemical characters. The findings of the present study demonstrate the potential of three mangrove actinomycetes in eastern Thailand to become a source of antimicrobial and anti-cancer metabolites.