Electrophoresis of motile bacteria.

For over 30 years the technique of microelectrophoresis has been used to study the surface properties of bacteria and other particles of microscopic size. Since flagella undoubtedly act as cellular surface components, they would be expected to contribute to the electrophoretic behavior of the cells. Likewise, vital motion might be expected to complicate electrophoretic measurements of flagellated cells. In preparing bacteria for the usual electrophoretic measurements, the bacterial cells are washed at least 3 times by centrifuging and resuspending in the desired buffer solution. This washing is necessary to remove the culture medium, waste products, and other constituents of the growth environment which might affect the cellular surfaces. Measurements are usually carried out within a few minutes after washing. In previous investigations (Harden and Harris, 1953; and Harris, 1953) of bacteria capable of vital motion, no motility due to flagella was observed. The objectives of this investigation were to prepare washed suspensions of motile bacteria for electrophoretic studies in such a way as to preserve their motility and to determine, if possible, the magnitude of the electrical potential necessary to overcome this vital motion.