Dengen (Dillenia serrata) is a native plant of Sulawesi with rhizosphere microorganisms that may serve as potential sources of antimicrobial compounds. This study aimed to isolate and characterize rhizosphere bacteria associated with Dengen plants in the Buttu Puang Forest Area, West Sulawesi, and evaluate their antimicrobial activity against Escherichia coli and Staphylococcus aureus. Rhizosphere soil samples were collected from a depth of 20 cm and subjected to bacterial isolation using the pour plate method on Nutrient Agar, followed by purification and phenotypic characterization through cell morphology, Gram staining, catalase, and endospore tests. Antimicrobial activity was evaluated using the disk diffusion method against E. coli and S. aureus. Three bacterial isolates, namely DB1, DB2, and DB3, were obtained. All isolates were rod-shaped, Gram-positive, and catalase-positive. Isolate DB1 did not form endospores, whereas DB2 and DB3 formed endospores. The isolates exhibited different antimicrobial activities. DB1 inhibited both E. coli and S. aureus, DB2 inhibited E. coli, and DB3 inhibited S. aureus. The results indicate that the Dengen rhizosphere is a potential source of indigenous bacteria with antimicrobial activity, with DB1 showing the broadest inhibitory spectrum.
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