Bioactivity of Bac70 Produced by Bacillus atrophaeus Strain DDBCC70

Recently, using antibacterial peptides has been considered as a strategy to manage the worldwide antibiotic-resistance crisis. Screening of Dasht-Desert Bacterial Culture Collection (DDBCC) for bacteriocin or bacteriocin-like producer was aimed in this study to introduce native antibacterial agent(s). Methods: In this study, 170 isolates were examined by the cross-streak method against G+ and G- indicators. Isolates with antimicrobial activity were compared using turbidity and well diffusion tests. The candidate isolate, DDBCC70, was molecularly and biochemically characterized. Then, the production of an antibacterial agent was physicochemically optimized. The supernatant was saturated ammonium sulfate. SDSPAGE and Thin-Layer Chromatography (TLC) analyses, cytotoxicity, and hemagglutination tests were performed. Results: First, 23 isolates were detected with antimicrobial activity against at least three of the indicator strains. DDBCC70 was distinguished with the broad-spectrum of antibacterial effects of the Cell-Free Supernatants (CFSs). The black pigments on BHI and a 98% similarity in 16S rDNA and similarity in biochemical tests confirmed the strain of DDBCC70 as Bacillus atrophaeus (B. atrophaeus). The highest amount of the antibacterial agent, Bac70, was obtained from the modified brain heart infusion medium. It was revealed that 70% ammonium sulfate-saturated Bac70 was 3.8 and 1.6 times more effective on Pseudomonas aeuroginosa (P. aeuroginosa) and Klebsiella pneumoniae (K. pneumoniae). Bac70, a >25 kDa protein and a safe compound for blood cells, neither agglutinated human erythrocyte nor lysed sheep blood. The purified bacteriocin-like molecule destroyed biofilms from P. aeruginosa and Staphylococcus aureus (S. aureus). Moreover, the fraction of Bac70 from the TLC plate showed higher inhibitory effects against K. pneumoniae. Conclusion: Based on the above-mentioned features, Bac70 is a potential alternative therapeutic agent in pharmaceutical, food preservative and biotech-related industries.