Toxin

The toxin that causes diphtheria is produced by a normally benign bacterium when infected with a certain virus.

Fructose is a toxin.

The neurological system is compromised by this toxin.

Until recently, the last time anyone in Harpers Ferry heard the call of a peregrine falcon, was fifty years ago. This crow-sized raptor, whose natural range is the rugged coastal areas in North America, was nearly decimated by the pesticide DDT. Since the toxin was banned in 1972, the peregrine has made a slow but dramatic recovery.

Botox's appeal as a skin enhancer was discovered by chance. Doctors knew that botulinum bacteria kill by paralyzing the diaphragm and preventing victims from breathing. The toxin the bacteria produce, botulin, blocks brain messages to muscles.

The blue-ringed octopus Hapalochlaena lunulata has tetrodotoxin, the deadly toxin it also releases in a bite, in their ink but the concentrations and effect in inking are not known.