Diversity and Antimicrobial Activities of Actinobacteria Isolated from Tropical Mangrove Sediments in Malaysia

Abstract

The aim of this study was to isolate and identify Actinobacteria from Malaysia mangrove forest and screen them for production of antimicrobial secondary metabolites. Eighty-seven isolates were isolated from soil samples collected at 4 different sites. This is the first report to describe the isolation ofStreptomyces, Mycobacterium, Leifsonia, Microbacterium, Sinomonas, Nocardia, Terrabacter, Streptacidiphilus, Micromonospora, Gordonia, andNocardioidesfrom mangrove in east coast of Malaysia. Of 87 isolates, at least 5 isolates are considered as putative novel taxa. NineStreptomycessp. isolates were producing potent antimicrobial secondary metabolites, indicating thatStreptomycesisolates are providing high quality metabolites for drug discovery purposes. The discovery of a novel species,Streptomyces pluripotenssp. nov. MUSC135Tthat produced potent secondary metabolites inhibiting the growth of MRSA, had provided promising metabolites for drug discovery research. The biosynthetic potential of 87 isolates was investigated by the detection of polyketide synthetase (PKS) and nonribosomal polyketide synthetase (NRPS) genes, the hallmarks of secondary metabolites production. Results showed that many isolates were positive for PKS-I (19.5%), PKS-II (42.5%), and NRPS (5.7%) genes, indicating that mangroveActinobacteriahave significant biosynthetic potential. Our results highlighted that mangrove environment represented a rich reservoir for isolation ofActinobacteria, which are potential sources for discovery of antimicrobial secondary metabolites.