Differential Stability of Aurein 1.2 Pores in Model Membranes of Two Probiotic Strains

Aurein 1.2 is an antimicrobial peptide from the skin secretion of an Australian frog. In previous experimental work, we reported a differential action of aurein 1.2 on two probiotic strains Lactobacillus delbrueckii subsp. Bulgaricus (CIDCA331) and Lactobacillus delbrueckii subsp. Lactis (CIDCA133). The differences found were attributed to the bilayer compositions. Cell cultures and CIDCA331-derived liposomes showed higher susceptibility than the ones derived from the CIDCA133 strain, leading to content leakage and structural disruption. Here, we used Molecular Dynamics simulations to explore these systems at atomistic level. We hypothesize that if the antimicrobial peptides organized themselves to form a pore, it will be more stable in membranes that emulate the CIDCA331 strain than in those of the CIDCA133 strain. To test this hypothesis, we simulated pre-assembled aurein 1.2 pores embedded into bilayer models that emulate the two probiotic strains. It was found that the general behavior of the systems depends on the composition of the membrane rather than the pre-assemble system characteristics. Overall, it was observed that aurein 1.2 pores are more stable in the CIDCA331 model membranes. This fact coincides with the high susceptibility of this strain against antimicrobial peptide. In contrast, in the case of the CIDCA133 model membranes, peptides migrate to the water-lipid interphase, the pore shrinks and the transport of water through the pore is reduced. The tendency of glycolipids to make hydrogen bonds with peptides destabilize the pore structures. This feature is observed to a lesser extent in CIDCA 331 due to the presence of anionic lipids. Glycolipid transverse diffusion (flip-flop) between monolayers occurs in the pore surface region in all the cases considered. These findings expand our understanding of the antimicrobial peptide resistance properties of probiotic strains.