noun (plural bacteria /-ˈti(ə)rēə/)
- a member of a large group of unicellular microorganisms that have cell walls but lack organelles and an organized nucleus, including some that can cause disease.
Bacteria are widely distributed in soil, water, and air, and on or in the tissues of plants and animals. Formerly included in the plant kingdom, they are now classified separately (as prokaryotes). They play a vital role in global ecology, as the chemical changes they bring about include those of organic decay and nitrogen fixation. Much modern biochemical knowledge has been gained from the study of bacteria because they grow easily and reproduce rapidly in laboratory cultures
mid 19th century: modern Latin, from Greek baktērion, diminutive of baktēria 'staff, cane' (because the first ones to be discovered were rod-shaped). Compare with bacillus
See bacteria (usage).