Membrane-damaging action of alveolysin from Bacillus alvei

We investigated membrane damage to human diploid, embryonic lung fibroblasts caused by highly purified alveolysin by measuring leakage of cytoplasmic markers and uptake of various metabolites, and we observed a leakage pattern typical of SH-activated cytolysins. However, the mode of membrane interaction resembled the mode of membrane interaction of theta-toxin from Clostridium perfringens rather than that of streptolysin O in the following respects: the activity on fibroblast membranes was high compared with the activity on sheep erythrocytes; the toxin did not bind irreversibly to fibroblast cytoplasmic membranes; considerable membrane damage was caused at 0 degrees C; and inhibition of amino acid uptake occurred in the absence of significant structural membrane damage. These findings imply that data on membrane effects caused by streptolysin O cannot be related indiscriminately to other SH-activated cytolysins. With regard to the mode of membrane interaction, two apparently different groups of SH-activated cytolysins exist.