Interaction of Tolaasin I and WLIP, Lipodepsipeptides of Pseudomonas tolaasii and P. 'reactans ', with Biological and Model Membranes

The activity of tolaasin I and White Line Inducing Principle (WLIP), produced in vitro by virulent strains of Pseudomonas tolaasii and P. “reactans”, respectively, was comparatively evaluated on red blood cells and large unilamellar vesicles. Tolaasin I and WLIP caused red blood cell haemolysis through a colloid-osmotic shock apparently caused by transmembrane pores formation. Both lipodepsipeptides were able to form channels in lipid vesicles. Their activity was dependent on the toxin concentration and liposomes composition, and independent on the pH. Studies of dynamic light scattering suggested a detergent-like activity for WLIP at high concentration (higher than 27 µM). This effect was not detected for tolaasin I at the concentrations tested (up to 28.2 µM).