Novel antimicrobial peptides derived from Brevibacillus laterosporus DSM 25 targeting MurT ligase exhibit broad-spectrum activity against drug-resistant pathogens

Abstract

The rapid rise of multidrug-resistant pathogens, poses a serious global threat, highlighting the need for new antimicrobial solutions. In this context, antimicrobial peptides (AMPs) have emerged as strong therapeutic candidates. Among potential targets, the MurT ligase, an ATP-dependent and highly conserved enzyme in Gram-positive bacteria that supports cell-wall stability and resistance towards antibiotics, stands out as an attractive yet underexplored candidate for anti-Gram-positive drug development. In this study, we predicted 100 potential AMPs from Brevibacillus laterosporus DSM 25 proteome, most of which possessed desirable AMP features such as cationicity, hydrophobicity, and non-toxicity. Docking and simulation analysis identified two peptides, BLA4 and BLA60, as the most stable and strong binders to MurT compared with its native ligand over 200 ns. Helical wheel projection analysis revealed a distinct amphipathic nature in both peptides, suggesting favorable membrane-penetration properties, which were subsequently validated through in vitro antibacterial assays. Both AMPs demonstrated potential antibacterial activity, with minimum inhibitory concentrations of 32 µg/mL against the drug-resistant Gram-positive MRSA strain and 64 µg/mL against the Gram-negative Klebsiella quasipneumoniae. Notably, time-kill kinetics displayed BLA60 as faster bactericidal in nature compared to BLA4. SEM analysis revealed peptide-induced membrane perforation and structural degradation in bacterial cells. Further in vitro and in vivo validation of these novel AMPs may support their potential as promising candidates and structural templates for broad-spectrum antibacterial drug development.