BACTERIUM

[bac.te.ri.um] n, pl -ria [NL, fr. Gk bakterion staff] (ca. 1849): any of a group (as Kingdom Procaryotae or Kingdom Monera) of prokaryotic unicellular round, spiral, or rod-shaped single-celled microorganisms that are often aggregated into colonies or motile by means of flagella, that live in soil, water, organic matter, or the bodies of plants and animals, and that are autotrophic, saprophytic, or parasitic in nutrition and important because of their biochemical effects and pathogenicity