What is a genus of common motile microörganisms (Spirobacteria) having the form of spiral-shaped filaments. One species is said to be the cause of relapsing fever called?

spirillum — A genus of common motile microörganisms (Spirobacteria) having the form of spiral-shaped filaments. One species is said to be the cause of relapsing fever. (Webster's 1913.)

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