Tetanus toxin is an extremely potent
neurotoxin produced by the vegetative cell of
Clostridium tetani in
anaerobic conditions, causing
tetanus. It has no known function for clostridia in the soil environment where they are normally encountered. It is also called
spasmogenic toxin, or
TeNT. The LD
50 of this toxin has been measured to be approximately 1 ng/kg, making it second only to
Botulinum toxin as the deadliest toxin in the world. However, these tests are conducted solely on mice which may react to the toxin differently from humans and other animals.