Genome mining, synthesis, antibacterial mechanism, and application of the gut commensal-derived antibacterial peptide CR24.

The growing occurrence of antimicrobial resistance has called for an urgent need to develop new sources of antimicrobial agents against multidrug-resistant strains. The trillions of microbes living in the gut become gradually a promising source of novel antimicrobial agents. In this study, we isolated a candidate strain with good antibacterial activity identified as Bacillus haynesii strain B1 from the sheep intestine and obtained a novel antimicrobial peptide through B. haynesii strain B1 genome mining, denoted as CR24. The CR24 showed an excellent and broad-spectrum antibacterial ability, no significant cytotoxicity, and very low levels of hemolytic activity. The mode of antibacterial action suggested that CR24 had bactericidal activity and could destroy cell membrane integrity, increase cell membrane permeability, and eventually lead to cell death. Moreover, we also demonstrated that APH (3')-IIIa phosphotransferase might provide a potential intracellular target for CR24 against neomycin-resistant Staphylococcus aureus. The anti-S. aureus skin wound infection revealed that CR24 exhibited good antibacterial properties in vivo and could accelerate wound healing and skin regeneration. In conclusion, these findings demonstrate CR24 is a promising and attractive candidate for further antimicrobial drug development and underscore the importance of developing new antimicrobial drugs from gut commensals.