Insights into the mode of action of the two-peptide lantibiotic lichenicidin

Lantibiotics are promising candidates to address the worldwide problem of antibiotic resistance. They belong to a class of natural compounds exhibiting strong activity against clinically relevant Gram-positive bacterial strains, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE). Lichenicidin is a class II two-peptide lantibiotic. The presence of the two mature peptides, Blia and Blip, is necessary for full activity against target bacteria. This work aims at clarifying the synergistic activity of both peptides in their interaction with the target membranes. The effect of lichenicidin was tested against S. aureus cells and large unilamellar vesicles. Lichenicidin increases the net surface charge of S. aureus, as shown by zeta-potential measurements, without reaching electroneutralization. In addition, lichenicidin causes cell surface perturbations that culminate in the leakage of its internal contents, as observed by atomic force microscopy. Blia seems to have low affinity for S. aureus, however, it contributes to increase the affinity of Blip, because together they present higher affinity than separately. In contrast, Blia seems to provide an anchoring site for lichenicidin in lipid II-containing membranes. Interestingly, Blip alone can induce high levels of membrane leakage, but this effect appears to be faster in the presence of Blia. Based on this information, we propose a mechanism of action of lichenicidin.

Automated summary

Lantibiotics are a promising solution to antibiotic resistance, particularly against Gram-positive bacteria like MRSA and VRE. Work on lichenicidin has shown that the interaction between the two peptides, Blia and Blip, is necessary for full activity against target bacteria. The mechanism of action involves an increase in net surface charge and observed cell surface perturbations that result in leakage of internal contents.