Isolation and Identification of Bacillus Species From Soil and Evaluation of Their Antibacterial Properties

Bacillus species are the predominant soil bacteria because of their resistant-endospore formation and production of essential antibiotics such as bacitracin. The aim of this study was to isolate Bacillus spp. from riverside soil and investigate their antimicrobial characteristics against some pathogenic bacteria. Fifty soil samples were collected from different sites of Bahmanshir riverside in Abadan city, Iran, and analyzed for the presence of Bacillus species. The media used in this research were nutrient broth and agar. Bacillus species were identified by their phenotypic and biochemical characteristics. The antimicrobial effects of Bacillus extract against the target bacteria including Escherichia coli, Staphylococcus aureus, Salmonella typhi, Shigella dysenteriae and Corynebacterium diphtheriae were examined. The identified Bacillus species included B. cereus (86.6%), B. subtilis (6.6%), B. thuringiensis (3.3%), and B. pumilus (3.3%). Evaluation of the antimicrobial activity of the extracted compounds was carried out against five different bacteria. Antibiotic production tests indicated that two Bacillus strains belong to B. cereus, which showed antimicrobial properties. The minimum inhibitory concentrations (MICs) of these compounds ranged between 8.34-33.34 mg/mL for the target bacteria. This study indicated that some Bacillus species have the potential to produce antimicrobial compounds which can be used to control microbial infections.