Correlation between membrane potential, cell shape, and motile activity in Amoeba proteus

The various motile activities and cell shapes of Amoeba proteus grown in Chalkley's solution are correlated with definitive electrical membrane potentials. The same correlations were found when definitive motile activities and cell shapes were experimentally induced by changing the pH of the culture medium. The highest values of membrane potential (−70 mV) were measured in monopodial amebae during active locomotion. In resting cells, which prevail in acid or basic media, the membrane potential decreases to −5 mV. In those resting cells, which also stop internal cytoplasmic movement at basic pH, the membrane potential turns positive (+9 mV − +30 mV).