Diversity and Bioactivities of Ulleung Island-Derived Marine Actinomycetes

Actinomycetes are key producers of bioactive secondary metabolites. In this study, sediment samples were collected using a grab sampler from the coast of Ulleung Island and inoculated on various agar media by stamping to isolate Actinomycetes. As a result, 69 Actinomycete strains were isolated and laboratory-cultured from the sediment samples. The isolates were assigned to the genera Streptomyces (44 strains), Nocardia (6 strains), Rhodococcus (6 strains), Mycobacterium (6 strains), Micromonospora (3 strains), Nocardioides (2 strains), Marmoricola (1 strain), and Oerskovia (1 strain) based on 16S rRNA gene sequence analysis. The antibacterial activity and potential toxicity of the culture broth extracts were tested for all isolates. Extracts from some strains exhibited strong antibacterial activity against Acinetobacter baumannii 04 and methicillin-resistant Staphylococcus aureus. Additionally, some extracts were toxic to brine shrimp. This study confirms that marine Actinomycetes from Ulleung Island encompass unique and diverse taxonomic groups and are a good source of bioactive natural products.