Electrokinetic movement of Escherichia coli in capillaries

The movement of Escherichia coli K-12 has been studied in capillaries with an 8 μm inside diameter under a DC electric field. At low applied voltages (< 0.2 V cm⁻¹), bacterial motility is the predominant mode of motion, with bacteria swimming, tumbling and moving unidirectionally towards the anode and the cathode, although a significant difference between the mean moving 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 exclusively towards the cathode.