Bioprospecting of cultivable actinobacteria from tropical peat swamp forest soil reveals Streptomyces with potent antimicrobial activity.

The rapid emergence of multidrug-resistant pathogens has become a major global health concern, highlighting the urgent need to discover new antimicrobial agents. Actinobacteria, particularly Streptomyces, are well known for their ability to produce diverse bioactive secondary metabolites with important pharmaceutical and agricultural applications. The purpose of this research was to isolate, characterize and evaluate the antimicrobial potential of actinobacteria isolated from tropical peat swamp forest soil. A total of 157 actinobacterial isolates were obtained and assigned to the genera Streptomyces, Microbispora, Microtetraspora, Micromonospora and Planosporangium. Preliminary antimicrobial screening revealed that 81 isolates (51.59%) exhibited inhibitory activity against at least one of the tested pathogens. Crude extracts from 17 selected isolates demonstrated antimicrobial activity with minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) values ranging from 0.024 to 12.50 mg mL-1. Several isolates exhibited strong antibacterial activity against Bacillus cereus TISTR 687 and Staphylococcus aureus ATCC 27853, while notable antifungal activity was observed against Candia albicans CBS 562. Molecular identification based on 16S rRNA gene sequencing revealed that all active isolates belonged to the genus Streptomyces, closely related to S. humi, S. yaanensis, S. bungoensis, S. murinus and S. malaysiense. These findings demonstrate that tropical peat swamp forest soils represent a valuable and underexplored reservoir of bioactive actinobacteria with promising antimicrobial potential. The study highlights the importance of peatland ecosystems as sources of novel microbial metabolites that may contribute to future pharmaceutical and biotechnological developments.