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. This synergistic effect seems to be in relation with interactions between iturin A and surfactin. Iturin A adsorbs to and penetrates into surfactin monolayers. Iturin A and surfactin are miscible and interact specifically in mixed monolayers.