TABLE 1.

Effect of ionic strength on the swimming speed of V. cholerae 1854 and V. alginolyticus VIO5

Strain– mediuma	NaCl (mM)	KCl (mM)	Motile fractionb (motile cells/total cells)	Swimming speedc (μm/s)
1854-LB	300		0.19	44.7
	200	100	0.33	56.8
	100	200	0.43	61.4
	200		0.65	83.0
	100		0.68	99.1
1854-VPG	300		0.44	84.0
	200	100	0.38	79.1
	100	200	0.40	71.7
	200		0.37	75.2
	100		0.40	74.2
VIO5-VPG	300		0.46	61.2
	200	100	0.43	61.4
	100	200	0.54	58.5
	200		0.47	61.8
	100		0.50	60.1

^aV. cholerae 1854 and V. alginolyticus VIO5 were cultured until late log phase in the indicated medium. 

^bCells harvested at late log phase were resuspended in TMN medium (pH 7.5) containing various concentrations of salts, and motility was measured and recorded on videotape. To suppress the directional change of swimming, 10 mM serine was added to the medium as an attractant. The motile fraction was determined by counting the number of motile cells among the total cells in one video image and averaging the findings in at least three images in one condition. 

^cThe average swimming speeds were obtained by measuring at least 20 swimming tracks of cells generated from the integrated video images.