Abstract
Clostridium novyi alpha-toxin and C. difficile toxins A and B (all 200 to 300 kDa) and C. botulinum C2-I toxin (50 kDa) caused a delayed and persistent retraction and rounding of microinjected cells. Microinjected phalloidin acted fast and reversibly. Unlike C2-I toxin, phalloidin passed through the intercellular junctions. Specific antitoxin applied to the medium did not prevent the action of microinjected C. novyi or C. difficile toxin B. Microinjected antitoxin protected against the toxins applied with the medium or injected into the same cells.