Background and Objectives: Pathogenic bacterial infection is one of the factors that can cause extensive losses in poultry farming. Pathogenic bacteria that infect domestic chickens (Gallus domesticus) include Escherichia coli. This study has investigated antimicrobial compounds from probiotic bacteria isolated from the digestive tract of domestic chickens originating from Takalar Regency, South Sulawesi, Indonesia. Materials and Methods: Lactic acid bacteria were grown on de Man-Ragosa-Sharpe agar medium for 24 hours. The bacterial isolate with the best inhibitory power was identified as Bacillus subtilis (B. subtilis), based on 16S RNA sequences. Antimicrobial activity of the selected lactic acid bacteria was tested on the pathogenic bacteria, E. coli and Staphylococcus aureus. Using well diffusion method. In this study, in silico study was conducted to examine the structure and binding affinity of lactic acid bacteria against E. coli and S. aureus. Molecular docking experiments were performed using the PyRx 0.8 software. Results: This study showed that the bacteria were B. subtilis strain PATA-5. The response of inhibition of antimicrobial compounds produced by B. subtilis strain PATA-5 maximum in the stationary phase. The bactericidal properties of B. subtilis strain PATA-5 were categorized as strong against Gram-negative E. coli, i.e., 30.5 mm, when compared to Gram-positive S. aureus, i.e., 17.5 mm. Conclusion: B. subtilis strain PATA-5 is capable to produce natural antibiotic cyclic lipopeptides, namely surfactin.
