Bacteria

Bacteria are one-celled life forms called organisms that can be seen only with a microscope.

Not all bacteria are harmful. Some bacteria that live in the body are helpful. For instance, some bacteria that live in the intestines, help digest food, destroy disease-causing organisms and provide nutrients.

But bacteria may also cause illness. Many disease-causing bacteria make powerful chemicals called toxins that damage cells and make you ill. Other bacteria can get into and damage tissues. Some infections caused by bacteria include:

• Strep throat.
• Tuberculosis.
• Urinary tract infections.