What is the deadliest organism?

The deadliest organism is often considered to be the bacterium Clostridium botulinum, which produces the potent botulinum toxin. This toxin is responsible for botulism, a severe form of food poisoning, and is estimated to be one of the most toxic substances known, with a lethal dose for humans as low as 2 nanograms per kilogram of body weight. Other contenders include certain venomous creatures, like the box jellyfish and the inland taipan snake, but the potency of botulinum toxin places it at the top in terms of lethality.