EFFECT OF TEMPERATURE ON MOTILITY AND CHEMOTAXIS OF ESCHERICHIA-COLI

The swimming velocity of E. coli at various constant temperatures increased with increasing temperature. The frequency of tumbling had a peak at 34.degree. C and was very low both at 20.degree. and at 39.degree. C. The swimming tracks near the surface of a slide glass showed curves, and the curvature increased with temperature. When the temperature of a bacterial suspension was suddenly changed, a transient change of the tumbling frequency was observed. A temperature drop induced a temporary increase in the tumbling frequency; a quick rise of temperature resulted in a temporary suppression of the tumbling. These dynamic responses to sudden changes of temperature were not observed in the smoothly swimming nonchemotactic strains bearing the mutations cheA, cheC and a mutant with the metF [methionine synthesis deficient] mutation under a smooth swimming condition.