BRIS soil actinomycetes and their antimicrobial activity

Microorganisms, particularly rare actinomycetes, are recognised as promising candidates for new drugs due to their diverse biosynthetic gene clusters. This study aimed to evaluate 155 actinomycetes isolated from the previously unexplored beach ridges interspersed with Swales (BRIS) environment in Setiu, Terengganu, Malaysia, for their antibacterial properties. Using the standard plug assay method these isolated were tested against a range of organisms, including Escherichia coli DSM 30083T, Bacillus subtilis DSM 10, Pseudomonas fluorescens DSM 50090, Klebsiella pneumoniae DSM 30104T, Micrococcus luteus DSM 20030T and Saccharomyces cerevisiae. Isolates AA12, AA13 and AA78, which exhibited the largest inhibition zones during primary screening, were selected for further analysis, including metabolite extraction, antimicrobial assays and identification through 16S rRNA gene sequencing. Results showed that 65% of all isolates demonstrated activity against at least one of the test organisms. Phylogenetic analysis revealed that isolates AA12, AA13 and AA78 are classified within the genera Amycolatopsis, Streptomyces and Microtetraspora, respectively. Additionally, the crude extracts from these isolates also produced inhibition zones in secondary screening against the same pathogens. These findings indicate that actinomycetes isolated from BRIS soil possess the potential to produce biologically active secondary metabolites and may serve as candidates for novel antimicrobial drug development.