A chemical, physical, or biological agent that causes disease or some alteration of the normal structure and function of an organism. Usually refers to poisonous substance produced during the metabolism and growth of certain microorganisms and some higher plant and animal species, or any poisonous isomer, homolog, or derivative of such a substance. It causes either permanent or reversible injury to the health of a living thing on contact or absorption, typically by interacting with biological macromolecules such as enzymes and receptors. Onset of effects may be immediate or delayed, and impairments may be slight or severe. (NCI)

A poison made by certain bacteria, plants, or animals, including insects.

A poison, usually one produced by a living organism.

Poison, usually protein, produced by higher plants, animals, or microorganisms that is toxic to other living organisms.

(toxins, biological) Specific, characterizable, poisonous chemicals, often PROTEINS, with specific biological properties, including immunogenicity, produced by microbes, higher plants (PLANTS, TOXIC), or ANIMALS.

Toxin, any substance poisonous to an organism. The term is sometimes restricted to poisons spontaneously produced by living organisms (biotoxins). Besides the poisons produced by such microorganisms as bacteria, dinoflagellates, and algae, there are toxins from fungi (mycotoxins), higher plants...