Definition of Bacteria

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Bacteria are single--celled microorganisms that lack nuclei and other organized cell structures. They are ubiquitous in nature, and are found in rocks, soil, snow and water, from the highest icy peaks to the deepest ocean trenches. Bacteria are vital to all other lifeforms, as they play a critical role in the recycling of nutrients.

They are also important to the physiology of other living organisms.

For instance, the bacteria in the human gut are important for our digestion.

Bacteria that can cause disease are called pathogenic bacteria. Controlling pathogenic bacteria with antibiotics has been perhaps the most important advance in medicine over the past century. Doctors usually classify bacteria as gram-positive or gram-negative based, based on whether they take on a purple color when exposed to gram stain. Bacteria come in a variety of shapes and sizes. They may be shaped like rods, spheres or spirals.

Pronunciation: bac-TEER-ee-uh

Also Known As: prokaryotes, bugs

Edited by Richard N. Fogoros, MD

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