Effect of staphylococcal alpha-toxin on mitochondrial Mg2+ (Na+, K+) activated adenosine triphosphatase

Ultrastructural changes in HEp-2 cells treated with staphylococcal alpha-toxin

The effect of highly purified staphylococcal alpha-toxin on HEp-2 neoplastic cells growing in culture was studied by electron microscopy. In addition to some nuclear modifications, the most significant morphological changes were in mitochondrial structure, alpha-toxin seems to induce a defined sequence of changes in mitochondrial configuration which can be summarized as an earlier phase of 'condensation' of mitochondrial structure and a later phase of mitochondrial swelling with an intermediate 'transitional' configuration. The significance of these findings is discussed in the light of the present state of knowledge of the biological characteristics of staphylococcal alpha-toxin.

The hemolysins of Staphylococcus aureus

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Uptake of fluorochrome-labelled exotoxins by different cell types in culture

The uptake of diphtheria toxin and of Staphylococcus alpha-toxin by two different human cell types cultured in vitro (the HEp-2 continuous cell line and human adult hepatocytes) was studied by fluorescence microscopy and phase-contrast microscopy. The behavior of these two bacterial exotoxins was quite different. Diphtheria toxin was incorporated into cells by pinocytosis, whereas alpha-hemolysin penetrated into the cytoplasm probably through lesions in the cell membrane. In addition, the penetration of diphtheria toxin into the cells was not inhibited by specific antiserum, whereas anti-alpha-haemolysin inhibited the penetration of alpha-tpxin through the cell membrane. The significance of these findings is discussed.