Fig. 1.

Cytotoxicity. A. ACHN cells were incubated at 37°C for 24 hours with serial dilutions of purified epsilon-toxin (■, 7.8 to 500 nM) or aerolysin (□, 0.04 to 2.5 nM). Cytotoxicity was assessed by addition of CellTiter Blue reagent to detect metabolically active cells. Results were normalized to the fluorescent signal from untreated cells (100%) and cells treated with 1% Triton (0%). Results represent the mean and standard deviation of quadruplicate samples. B. ACHN cells were incubated at 37°C for 90 minutes or 24 hours with 500 nM epsilon-toxin or 2.5 nM aerolysin. Cytotoxicity was assessed by addition of CellTiter Blue reagent to detect metabolically active cells. Results were normalized to the fluorescent signal from untreated cells (100%) and cells treated with 1% Triton (0%). Results represent the mean and standard deviation of triplicate samples. C. ACHN cells were incubated at 37°C for 90 minutes with 500 nM epsilon-toxin or 2.5 nM aerolysin. Extracellular LDH was measured using the CytoTox-ONE Homogeneous Membrane Integrity Assay (Promega). Results represent the mean and standard deviation of triplicate samples. These experiments were performed at least three times with similar results.