Today's society is well aware that bacteria can cause many illnesses. Sometimes, however, it is not the bacteria themselves that actually cause the damage to our bodies. In some instances, the symptoms of the diseases are actually the result of exotoxins circulating throughout the body.
An exotoxin is a special type of molecule that is secreted by a microorganism. Although the blame is usually put on bacteria, exotoxins are also found to be produced by fungi, algae, and other organisms. As the name suggests, these molecules are toxins and cause damage to our body's cells. They way they inflict their damage varies depending on the type of toxin, but most exert their power by interfering with the normal metabolism of the cell are entirely destroying the cell.
The prefix "exo" indicates that these types of toxins exist outside the bacterial cell itself. After being produced inside the cell body, the toxin is released from the cell and into the environment. If this bacteria in located within a human body, that toxin is released into the blood steam where it can travel and cause damage throughout the body. This is slightly different from "endotoxins", which remain inside the bacterial cell. It isn't until the bacteria is destroyed and bursts (called lysis), which releases all the bacteria's contents into the blood steam, including the toxins.
One very common type of exotoxin is called tetanospasmin. This is the toxin responsible for the disease Tetanus, also called Lockjaw. This toxin is produced by a species of bacteria called C. Tetani and when it enters the body, such as through an open wound, it causes the muscles of the body to contract and remain contracted for a long period of time. This makes it difficult to move, swallow, or do other tasks involving your muscles. Luckily, a vaccine to prevent the effects of the Tetanus disease has been developed. This vaccine prepares your body's immune system by exposing it to an inactive form of the tetanospamin toxin. By doing this, your body is able to quickly recognize the toxin in the future if an infection occurs. Then your immune system is able to attack and destroy the toxin before symptoms appear.
Exotoxins are a fascinating but potentially dangerous class of molecules. These bacteria by-products have caused damage to people for centuries, but thanks to modern medicine, we are able to understand how these toxin affect the body and we are now able to manufacture effective treatments to prevent their harmful effects.