A genus of strictly aerobic bacteria (family Brucellaceae) containing minute, gram-negative non-spore-bearing, coccobacilli. Motile and nonmotile species occur; motile cells are peritrichous. The metabolism of these organisms is respiratory. They require nicotinic acid, cysteine, and methionine; hemin (X factor) and coenzyme I (V factor) are not required. They are parasites and pathogens of the mammalian respiratory tract; type species is Bordetella pertussis. [J. Bordet]