Fengycin induces ion channels in lipid bilayers mimicking target fungal cell membranes

Abstract

The one-sided addition of fengycin (FE) to planar lipid bilayers mimicking target fungal cell membranes up to 0.1 to 0.5 μM in the membrane bathing solution leads to the formation of well-defined and well-reproducible single-ion channels of various conductances in the picosiemens range. FE channels were characterized by asymmetric conductance-voltage characteristic. Membranes treated with FE showed nonideal cationic selectivity in potassium chloride bathing solutions. The membrane conductance induced by FE increased with the second power of the lipopeptide aqueous concentration, suggesting that at least FE dimers are involved in the formation of conductive subunits. The pore formation ability of FE was not distinctly affected by the molecular shape of membrane lipids but strongly depended on the presence of negatively charged species in the bilayer. FE channels were characterized by weakly pronounced voltage gating. Small molecules known to modify the transmembrane distribution of electrical potential and the lateral pressure profile were used to modulate the channel-forming activity of FE. The observed effects of membrane modifiers were attributed to changes in lipid packing and lipopeptide oligomerization in the membrane.

1,3-Thiazine, 1,2,3,4-Dithiadiazole, and Thiohydrazide Derivatives Affect Lipid Bilayer Properties and Ion-Permeable Pores Induced by Antifungals

“…It is known that the antifungal cyclic lipopeptide produced by Bacillus subtilis , Fen, acts by making the plasma membrane of the target cell more permeable ( Vanittanakom et al, 1986 ; Patel et al, 2011 ). The Fen-induced increase in membrane permeability is related to the formation of ion channels of various conductances and non-ideal cationic selectivity ( Zakharova et al, 2019 ). It was also shown that the alteration in membrane dipole potential does not affect the pore-forming ability of this lipopeptide while the membrane adsorption of small molecules that decreased the lipid packing density enhances the steady-state Fen-induced transmembrane current ( Zakharova et al, 2019 ).…”

“…The Fen-induced increase in membrane permeability is related to the formation of ion channels of various conductances and non-ideal cationic selectivity ( Zakharova et al, 2019 ). It was also shown that the alteration in membrane dipole potential does not affect the pore-forming ability of this lipopeptide while the membrane adsorption of small molecules that decreased the lipid packing density enhances the steady-state Fen-induced transmembrane current ( Zakharova et al, 2019 ). Thus, the significant effects of C3, C6, and C8 on lipid packing ( Figure 3 and Table 4 ) indicate their potential applications for up-regulating the pore-forming ability of Fen.…”

“…Table 3 summarizes the data obtained. The almost 10-fold increase in I ∞ value in the presence of C6 can be explained by the strong dependence of the pore forming ability of Fen on the presence of negatively charged species in the bilayer ( Zakharova et al, 2019 ) or the more pronounced disordering effect of C6 on negatively charged bilayers containing PG compared to neutral ones made from PC. The electrostatic repulsion of the negatively charged lipids and C6 molecules should cause a significant decrease in the membrane packing density impacting the oligomerization of lipopeptide molecules that form pores.…”

“…Fen-induced transmembrane current (Zakharova et al, 2019). Thus, the significant effects of C3, C6, and C8 on lipid packing (Figure 3 and Table 4) indicate their potential applications for up-regulating the pore-forming ability of Fen.…”

Genetic and Physiological Characterization of the Antibacterial Activity ofBacillus subtilissubsp.inaquosorumStrain T1 Effective AgainstpirABVp-Bearing Vibrioparahaemolyticus

“…The mode of action of many Bacillus spp. NRPS-and PKS-derived anitmicrobials is through membrane perturbation or depolarization (15), e.g., fengycin (41) and iturin A (42), blockage of peptidoglycan biosynthesis, e.g., bacilysin (34), or selective inhibition of protein synthesis, e.g., difficidin (34). Regardless of mechanism, both co-culture and cell-free supernatant experiments demonstrated that D4 was capable of overcoming the T1 NRPS-PKS inhibitory activity, with growth levels reaching those obtained for untreated cultures.…”