Selection of antimicrobial peptides derived from Bacillus cereus: Investigation of their antimicrobial activity and mechanism of action against Staphylococcus aureus

Staphylococcus aureus is a prevalent pathogenic bacterium associated with foodborne illnesses, posing significant concerns for food safety. This study explored the effectiveness of Bacillus cereus in eliminating S. aureus in mixed culture experiments. Proteomics results revealed down-regulation of protein expression, particularly the ATP synthesis subunit Beta protein, as a potential mechanism for this elimination. Bioinformatics analysis identified a promising antimicrobial peptide sequence (KLVHRARRIQFFLSQNFH) named BaD9. BaD9 exhibited a minimum bactericidal concentration (MBC) against S. aureus of 3.91 mu g/mL, achieving bacterial eradication within 0.5 h. Further investigations, including transmission electron microscopy (TEM), demonstrated BaD9's ability to disrupt the cell membrane of S. aureus. Treatment of S. aureus genomic DNA with a high concentration of BaD9 resulted in abnormal electrophoresis patterns, indicating interference with DNA integrity. Additionally, BaD9 induced changes in its secondary structure. Notably, mammalian red blood cell experiments confirmed the non- hemolytic nature of BaD9 at 8 x MBC concentration. These findings contribute valuable insights into the potential antibacterial mechanisms of B. cereus against S. aureus, offering a reference for antibacterial peptide screening. BaD9's demonstrated efficacy and safety profile support its potential application as a promising antibacterial resource.