The Effect of “Low Voltage” X-rays on the Electrophoretic Migration Velocity, Viability and pH of Escherichia coli Suspensions

Bacteria under normal environmental conditions have a negative electrophoretic potential. Recently two of us, Lisse and Tittsler (1931), reported that the irradiation of Escherichia coli with ultraviolet or even Mazda bulb rays affected the electrophoretic migration velocity, viability, lysis and pH of an aqueous suspension. As a result of these studies we came to the conclusion that when these rays kill bacteria they first stimulate, a process accompanied by an increase in the electrophoretic migration velocity, and later destroy, a process accompanied by a decrease in this velocity. In brief, this work suggested the hypothesis that stimulation and injury are reversible processes in which the electrophoretic potential tends to return to normal, whereas death is an irreversible process in which there is no such return. The validity of this hypothesis may be questioned in view of the fact that Winslow, et al. (1923) reported "that heat-killed bacterial cells exhibit essentially the same curve of migration velocity as that of living cells." According to the principles of photochemistry one is led to believe that certain effects, for example, those observed after