Bacteria

(bak-TEER-ee-uh) A large group of single-cell microorganisms. Some cause infections and disease in animals and humans. The singular of bacteria is bacterium.

(singular: Bacterium) Single-celled organisms that are found throughout nature and can be beneficial or cause disease.

A single-celled organism. Bacteria are found throughout nature and can be beneficial or pathogenic. See also cell

Any of numerous unicellular microorganisms, existing either as free living organisms or as parasites, and having a broad range of biochemical, often pathogenic properties.

Single-celled organisms, free-living or parasitic, that break down the wastes and bodies of dead organisms, making their components available for reuse by other organisms.

A small single-cell organism. Bacteria do not have an organized nucleus, but they do have a cell membrane and protective cell wall. Bacteria can be used to ferment sugars to ethanol.

One-celled organisms. Many act as decomposers that break down dead organic matter into substances that dissolve in water and are used as nutrients by plants.