spirillum

‖n. [ NL., dim. of L. spira a coil. ] 1. (Biol.) A genus of common gram-negative motile microorganisms (family Spirillaceae) having the form of spiral-shaped filaments. They are obligately microaerophilic, and do not ferment carbohydrates. Stedman. [ 1913 Webster ]

2. A species of bacteria (Borrelia recurrentis, also known as Obermeier's spirillum), once believed to belong to the genus Spirillum, which causes relapsing fever. [ PJC ]