The antibiotic resistance crisis has been a global health threat for decades, because bacterial pathogens, viruses, and other parasites evolve to resist current antibiotics. This has led to unmet needs for the discovery of new compounds that are different from the current antimicrobials. Antimicrobial peptides (AMPs), as promising alternatives to conventional antibiotics, have attracted growing interest owing to their lower likelihood of causing bacteria to develop resistance compared with antibiotics. In this study, we rationally designed a series of peptides, evaluated their antibacterial activities, and investigated their modes of action against bacteria.

Bacterial initiation factor 1 (IF1) is a small protein but plays a critical role in regulating bacterial protein biosynthesis. According to our structural studies on IF1 proteins from three representative bacterial pathogens—Pseudomonas aeruginosa, Clostridioides difficile, and Helicobacter pylori—and their interactions with the 30S ribosomal subunits, we designed a series of IF1-derived short peptides. These peptides were tested for inhibitory activities against various bacteria, including Gram-positive and Gram-negative strains. The results showed that the MIC (minimum inhibitory concentration) of IF1-peptides is as low as 20 uM against P. aeruginosa ATCC 47085, 60 uM against C. difficile ATCC 43593, and 18 uM against Staphylococcus epidermitis ATCC 12228 and Bacillus cereus ATCC 14579. Further investigation of the mode of action showed that IF1-derived peptides did not affect the bacterial membrane integrity based on the SEM results; however, they displayed dose-dependent inhibition against bacterial protein synthesis. These results suggest IF1-derived peptides as new type of antibacterial candidate. Since bacterial IF1 is a highly conserved element of the prokaryotic translational apparatus, these results provide a potential avenue for the rational design of new antimicrobials.