sentences:  Rickettsia
  
  Rickettsia is a genus of nonmotile, Gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long).The term "rickettsia" has nothing to do with rickets (which is a deficiency disease resulting from lack of vitamin D); the bacterial genus "Rickettsia" was named after Howard Taylor Ricketts, in honour of his pioneering work on tick-borne spotted fever.