Effect of the lipopeptide antibiotic, iturin A, on morphology and membrane ultrastructure of yeast cells.

The effects of iturin A, at fungicidal concentrations, on yeast cells were studied by scanning electron microscopy and by transmission electron microscopy. A depression, observed in each iturin A-treated cell, was the consequence of the release of electrolytes and other cytoplasmic components. Iturin A passes through the cell wall and disrupts the plasma membrane with the formation of small vesicles and the aggregation of intramembranous particles.

Effect of iturin A, a lipopeptide from Bacillus subtilis on morphology and ultrastructure of human erythrocytes.

Iturin A, a lipopeptide from Bacillus subtilis, induced morphological modifications of human erythrocytes and a concomitant release of exovesicles. The modifications depended on the lipopeptide concentration and on the incubation time. Crenation of cells occurred while invaginations appeared when the incubation time was increased.

Surfactin/iturin A interactions may explain the synergistic effect of surfactin on the biological properties of iturin A.

Iturin A and surfactin are two lipopeptides extracted from a same strain of Bacillus subtilis. Iturin A possesses antibiotic and antifungal activities and surfactin is a strong surfactant. The presence of surfactin, at a concentration at which, alone, it is inactive, increases to a very large extent the haemolysis percent induced by iturin A.

Interactions of bioactive lipopeptides, iturin A and surfactin from Bacillus subtilis.

The antifungal activity of iturin A and its interaction with erythrocyte membranes were enhanced in the presence of surfactin. The modification of the properties of iturin A was explained by the formation of mixed iturin A-surfactin micelles. Such mixed micelles were easily generated when both lipopeptides were in aqueous solutions in the absence of mineral salts but the formation of these micelles did not occur when the solutions contained a high molarity of mineral cations.