An exotoxin is a soluble protein excreted by a microorganism, including bacteria, fungi, algae, and protozoa. An exotoxin can cause damage to the host by destroying cells or disrupting normal cellular metabolism.Both gram negative and gram positive bacteria produce exotoxins. They are highly potent and can cause major damage to the host. Exotoxins may be secreted, or, similar to endotoxins, may be released during lysis of the cell.Most exotoxins can be destroyed by heating. They may exert their