Antimicrobial activity of Bacillus species isolated from Yemeni soils against some human pathogens

Bacillus species represent one of the most dominant soil bacteria and are capable of producing diverse metabolites with antimicrobial properties. This study aimed to isolate Bacillus spp. from Yemeni soils and evaluate their antimicrobial activity. Thirty soil samples were collected, and the isolates were characterized using phenotypic and biochemical tests. Their antimicrobial potential was assessed against Staphylococcus aureus, Escherichia coli, Pseudomonas sp., Salmonella sp., and Candida albicans using agar disc and well diffusion methods. In agar disc assays, the strongest inhibitory effects were observed against Salmonella sp. (13–32.5 mm), followed by E. coli (13–25.4 mm), C. albicans (10–18.5 mm), and S. aureus (10–15.5 mm). Five isolates exhibited antibacterial activity against Salmonella sp. in well diffusion assay. These results highlight the significant antimicrobial potential of Bacillus isolates derived from Yemeni soils. Further studies are recommended to identify bioactive metabolites and explore their suitability for the development of novel therapeutic agents.