The mechanism of electric-current generation by Escherichia coli JAM 1016 and the effect of an anion-exchange resin on the amount of the current were investigated by using the electrode system developed by MATSUNAGA et al.(1). The current was increased by addition of succinic acid or glucose, and the increased current was diminished by arsenite. Rotenone and antimycin A3, inhibitors of the respiratory chain, increased the current at lower concentrations and decreased it at higher. These results indicate that the current primarily results from respiratory activity, and that the source of electrons transferred to the electrode is located along the respiratory process. The current was diminished by addition of the resin. This result suggests that electrons can be transferred from cells to resin as well as to the electrode. The transfer of electrons to the resin changed the rate of glucose uptake and enhanced the respiratory activity of the organism.Recently MATSUNAGA et al. (1) developed an electrode system for measuring microbial populations. They reported that Saccharomyces cerevisiae and Lactobacillus fermenti generated electric current when they came into contact with the electrode and that the amount of the current was proportional to the microbial population. But the mechanism of current generation was not fully understood.On the other hand, the importance of the liquid-solid interface to microorganisms has been asserted by many authors. I supposed that the interface might affect the current, and that through this effect the physiological properties of microorganisms might be changed.On this assumption I studied the following: (1) the mechanism of the current generation by E. coli; (2) the effect of an anion-exchange resin (Dowex 1) on the current; (3) the effect of the resin on the rates of glucose uptake and product formation.