Gram-negative, motile, straight rods. Cells are 0.5 to 0.8 um wide and 2 to 5 um long with round ends and two to five unipolar flagella. The flagella are unsheathed. In general, C. showae strains are catalase positive while C. rectus strains are catalase negative. The G + C content of the DNA is 44-46%.