Isolation and characterization of antimicrobial peptides from Lactobacillus: Exploring mechanisms of action

The rise of antibiotic-resistant bacteria necessitates the development of novel antimicrobial agents. In this study, antimicrobial peptides (AMPs) were isolated from Lactobacillus sp., yielding Bioactive Peptide I (BAP I) and Bioactive Peptide III (BAP III). Purified via gel filtration chromatography (GFC), these peptides were characterized by MALDI-TOF MS and SDS-PAGE, which confirmed their molecular masses as 4168.14 Da and 8076.45 Da, respectively, and verified their high purity. Both peptides demonstrated potent antibacterial activity against Pseudomonas aeruginosa, Streptococcus sanguinis, Bacillus cereus, and Staphylococcus aureus, with BAP I exhibiting superior efficacy. This enhanced activity is likely due to its amphipathic structure and hydrophobic C-terminal region, which promote effective bacterial membrane disruption as evidenced by FE-SEM imaging. In addition to compromising membrane integrity, both BAP I and BAP III inhibited bacterial DNA polymerase activity, as shown by reduced PCR product formation. Complementary Circular Dichroism (CD) spectroscopy analysis indicated that peptide binding induced conformational changes in Taq polymerase, reducing its α-helical and β-sheet content while increasing the proportion of random coil structures—thus enhancing the enzyme's flexibility. Molecular docking and dynamics studies further revealed stable interactions between the peptides and the enzyme, suggesting a dual mechanism of action that targets both the bacterial membrane and DNA replication processes. Collectively, these findings highlight the significant potential of BAP I and BAP III as novel antimicrobial agents against multidrug-resistant infections. Future research should focus on evaluating their safety and clinical efficacy, as well as exploring their synergistic potential with existing antibiotics to advance these peptides as therapeutic alternatives.