Electrokinetic movement of Escherichia coli in capillaries

The movement of Escherichia coli K-12 has been studied in capillaries with an 8 mu m inside diameter under a DC electric field. At low applied voltage s (< 0.2 V cm(-1)), bacterial motility is the predominant mode of motion, w ith bacteria swimming, tumbling and moving unidirectionally towards the ano de and the cathode, although a significant difference between the mean movi ng speeds towards the two electrodes was observed. When the electric field was removed, the mean swimming speeds were the same for both directions. At higher voltages, all the cells were swept by electro-osmotic flow exclusiv ely towards the cathode.