Clostridium botulinum
Botulinum toxin is a neurotoxin present in the cytoplasm of the anaerobic bacterium "Clostridium botulinum". It binds presynaptically with high affinity to sites on cholinergic nerve terminals, decreasing release of acetylcholine, thereby blocking neuromuscular transmission, and causing flaccid muscle paralysis. Crotoxin appears to act similarly.